6487 Picoammeter/Voltage Source Keithley Manual

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Model 6487 Picoammeter/Voltage Source
Reference Manual
6487-901-01 Rev. B / March 2011

G R E A T E R

M E A S U R E

O F

C O N F I D E N C E

Model 6487
Picoammeter/Voltage Source
Reference Manual

© 2002-2011, Keithley Instruments, Inc.
Cleveland, Ohio, U.S.A.
All rights reserved.
Any unauthorized reproduction, photocopy, or use the information herein, in whole or in part,
without the prior written approval of Keithley Instruments, Inc. is strictly prohibited.
All Keithley Instruments product names are trademarks or registered trademarks of Keithley
Instruments, Inc. Other brand names are trademarks or registered trademarks of their respective
holders.
The Lua 5.0 software and associated documentation files are copyright © 1994-2008, Tecgraf,
PUC-Rio. Terms of license for the Lua software and associated documentation can be accessed at
the Lua licensing site (http://www.lua.org/license.html).
Keithley's standard terms and conditions of sale in effect at the time of acceptance of buyer's order
by Keithley shall apply to all purchase of goods and performance of services from Keithley, to the
exclusion of any additional or different terms and conditions, including any terms or conditions
which buyer may purport to apply under any buyer's request for quotation, purchase order or similar
document, or which buyer may offer in response to these terms. A copy of Keithley's current terms
can be accessed at http://www.keithley.com/company/termsandconditions (these "Terms"). To
obtain a printed copy of these Terms, please contact your local sales office or send an email to
orders@keithley.com. Buyer's assent to these Terms, and only these Terms, shall be conclusively
presumed from buyer's acceptance of delivery of the products and/or services provided by Keithley.

Document number: 6487-901-01 Rev. B / March 2011

Safety Precautions

The following safety precautions should be observed before using this product and any associated instrumentation.
Although some instruments and accessories would normally be used with non-hazardous voltages, there are
situations where hazardous conditions may be present.
This product is intended for use by qualified personnel who recognize shock hazards and are familiar with the safety
precautions required to avoid possible injury. Read and follow all installation, operation, and maintenance
information carefully before using the product. Refer to the user documentation for complete product specifications.
If the product is used in a manner not specified, the protection provided by the product warranty may be impaired.
The types of product users are:
Responsible body is the individual or group responsible for the use and maintenance of equipment, for ensuring
that the equipment is operated within its specifications and operating limits, and for ensuring that operators are
adequately trained.
Operators use the product for its intended function. They must be trained in electrical safety procedures and proper
use of the instrument. They must be protected from electric shock and contact with hazardous live circuits.
Maintenance personnel perform routine procedures on the product to keep it operating properly, for example,
setting the line voltage or replacing consumable materials. Maintenance procedures are described in the user
documentation. The procedures explicitly state if the operator may perform them. Otherwise, they should be
performed only by service personnel.
Service personnel are trained to work on live circuits, perform safe installations, and repair products. Only properly
trained service personnel may perform installation and service procedures.
Keithley Instruments products are designed for use with electrical signals that are rated Measurement Category I
and Measurement Category II, as described in the International Electrotechnical Commission (IEC) Standard IEC
60664. Most measurement, control, and data I/O signals are Measurement Category I and must not be directly
connected to mains voltage or to voltage sources with high transient over-voltages. Measurement Category II
connections require protection for high transient over-voltages often associated with local AC mains connections.
Assume all measurement, control, and data I/O connections are for connection to Category I sources unless
otherwise marked or described in the user documentation.
Exercise extreme caution when a shock hazard is present. Lethal voltage may be present on cable connector jacks
or test fixtures. The American National Standards Institute (ANSI) states that a shock hazard exists when voltage
levels greater than 30V RMS, 42.4V peak, or 60VDC are present. A good safety practice is to expect that hazardous
voltage is present in any unknown circuit before measuring.
Operators of this product must be protected from electric shock at all times. The responsible body must ensure that
operators are prevented access and/or insulated from every connection point. In some cases, connections must be
exposed to potential human contact. Product operators in these circumstances must be trained to protect
themselves from the risk of electric shock. If the circuit is capable of operating at or above 1000 volts, no conductive
part of the circuit may be exposed.
Do not connect switching cards directly to unlimited power circuits. They are intended to be used with impedancelimited sources. NEVER connect switching cards directly to AC mains. When connecting sources to switching cards,
install protective devices to limit fault current and voltage to the card.
Before operating an instrument, make sure the line cord is connected to a properly grounded power receptacle.
Inspect the connecting cables, test leads, and jumpers for possible wear, cracks, or breaks before each use.
When installing equipment where access to the main power cord is restricted, such as rack mounting, a separate
main input power disconnect device must be provided in close proximity to the equipment and within easy reach of
the operator.
04/09

For maximum safety, do not touch the product, test cables, or any other instruments while power is applied to the
circuit under test. ALWAYS remove power from the entire test system and discharge any capacitors before:
connecting or disconnecting cables or jumpers, installing or removing switching cards, or making internal changes,
such as installing or removing jumpers.
Do not touch any object that could provide a current path to the common side of the circuit under test or power line
(earth) ground. Always make measurements with dry hands while standing on a dry, insulated surface capable of
withstanding the voltage being measured.
The instrument and accessories must be used in accordance with specifications and operating instructions, or the
safety of the equipment may be impaired.
Do not exceed the maximum signal levels of the instruments and accessories, as defined in the specifications and
operating information, and as shown on the instrument or test fixture panels, or switching card.
When fuses are used in a product, replace with the same type and rating for continued protection against fire hazard.
Chassis connections must only be used as shield connections for measuring circuits, NOT as safety earth ground
connections.
If you are using a test fixture, keep the lid closed while power is applied to the device under test. Safe operation
requires the use of a lid interlock.
If a

screw is present, connect it to safety earth ground using the wire recommended in the user documentation.

The ! symbol on an instrument means caution, risk of danger. The user should refer to the operating instructions
located in the user documentation in all cases where the symbol is marked on the instrument.
The
symbol on an instrument means caution, risk of danger. User standard safety precautions to avoid
personal contact with these voltages.
The
The

symbol on an instrument shows that the surface may be hot. Avoid personal contact to prevent burns.
symbol indicates a connection terminal to the equipment frame.

If this
symbol is on a product, it indicates that mercury is present in the display lamp. Please note that the lamp
must be properly disposed of according to federal, state, and local laws.
The WARNING heading in the user documentation explains dangers that might result in personal injury or death.
Always read the associated information very carefully before performing the indicated procedure.
The CAUTION heading in the user documentation explains hazards that could damage the instrument. Such
damage may invalidate the warranty.
Instrumentation and accessories shall not be connected to humans.
Before performing any maintenance, disconnect the line cord and all test cables.
To maintain protection from electric shock and fire, replacement components in mains circuits - including the power
transformer, test leads, and input jacks - must be purchased from Keithley Instruments. Standard fuses with
applicable national safety approvals may be used if the rating and type are the same. Other components that are
not safety-related may be purchased from other suppliers as long as they are equivalent to the original component
(note that selected parts should be purchased only through Keithley Instruments to maintain accuracy and
functionality of the product). If you are unsure about the applicability of a replacement component, call a Keithley
Instruments office for information.
To clean an instrument, use a damp cloth or mild, water-based cleaner. Clean the exterior of the instrument only. Do
not apply cleaner directly to the instrument or allow liquids to enter or spill on the instrument. Products that consist
of a circuit board with no case or chassis (e.g., data acquisition board for installation into a computer) should never
require cleaning if handled according to instructions. If the board becomes contaminated and operation is affected,
the board should be returned to the factory for proper cleaning/servicing.

Table of Contents
1

Getting Started
Introduction ................................................................................ 1-2
Overview of this manual ............................................................ 1-2
General information ................................................................... 1-3
Warranty information .......................................................... 1-3
Contact information ............................................................ 1-3
Safety symbols and terms ................................................... 1-3
Unpacking and Inspection .................................................. 1-3
Reference manual ............................................................... 1-4
Additional references .......................................................... 1-4
Power-up .................................................................................... 1-5
Line power connection ........................................................ 1-5
Line frequency .................................................................... 1-6
Power-up sequence ............................................................. 1-7
Front panel operation ................................................................. 1-8
Status and error messages .......................................................... 1-8
Default settings .......................................................................... 1-8
Front panel setup operation ................................................. 1-9
Remote setup operation ...................................................... 1-9
Menus ....................................................................................... 1-12
Main menus ....................................................................... 1-12
Configuration menus ......................................................... 1-13
SCPI programming .................................................................. 1-14
Optional command words ................................................. 1-14
Query commands .............................................................. 1-14

2
Measurement Concepts
and Connections
Connection fundamentals ...........................................................
Input connector ...................................................................
Voltage source output connectors .......................................
Maximum input levels ........................................................
Low-noise input cables .......................................................
Voltage source test leads .....................................................
Basic connections to DUT .........................................................
Current measurement connections ......................................
Ohms measurement connections ........................................
Voltage source connections .................................................
Voltages greater than 505V .................................................
Noise and safety shields ......................................................
Using a test fixture .....................................................................

2-2
2-2
2-2
2-3
2-3
2-4
2-4
2-4
2-5
2-6
2-6
2-8
2-8

General purpose test fixture ................................................ 2-9
Model 8009 resistivity test fixture ..................................... 2-11
Floating measurements ...................................................... 2-12
Interlock .................................................................................... 2-13
Interlock connections ........................................................ 2-13
Interlock operation ............................................................ 2-14
Interlock programming ...................................................... 2-14
Analog output ........................................................................... 2-14
Measurement considerations .................................................... 2-16

3
Measurements and
Sourcing Voltage
Measurement overview ............................................................... 3-2
Current measurements ......................................................... 3-2
Voltage source ..................................................................... 3-2
Performance considerations ........................................................ 3-3
Warm-up period ................................................................... 3-3
Voltage offset correction ..................................................... 3-3
Autozero .............................................................................. 3-3
Zero check and zero correct ................................................ 3-4
Current measurements ................................................................ 3-7
Procedure ............................................................................. 3-7
Programming example ...................................................... 3-11
Ohms measurements ................................................................. 3-11
Overview ........................................................................... 3-11
Procedure ........................................................................... 3-12
SCPI programming — ohms measurements ..................... 3-14
Programming example — ohms measurements ................ 3-15
Voltage source operation .......................................................... 3-15
Voltage source edit keys .................................................... 3-15
Configuring the voltage source ......................................... 3-15
Sourcing voltage ................................................................ 3-16
Operate considerations ...................................................... 3-18
Compliance indication ....................................................... 3-18
Open interlock indication .................................................. 3-18
SCPI commands — voltage source ................................... 3-19
Programming example — voltage ..................................... 3-20
Alternating voltage ohms mode ................................................ 3-21
Overview ........................................................................... 3-21
Storing A-V ohms readings ............................................... 3-23
Recalling A-V ohms readings ........................................... 3-24
Operating considerations ................................................... 3-25
SCPI commands — A-V ohms ......................................... 3-28
Programming example — A-V ohms measurements ........ 3-31

4
Range, Units, Digits,
Rate, and Filters
Range, units, and digits .............................................................. 4-2
Range .................................................................................. 4-2
Units .................................................................................... 4-3
Digits ................................................................................... 4-4
SCPI programming — range and digits .............................. 4-4
Rate ............................................................................................ 4-6
SCPI programming — rate ................................................. 4-7
Damping ..................................................................................... 4-8
Filters ......................................................................................... 4-8
Median filter ........................................................................ 4-9
Median filter control ........................................................... 4-9
Digital filter ....................................................................... 4-10
SCPI programming — filters ............................................ 4-12

Relative, mX+b, m/X+b, and log
Relative ......................................................................................
Setting and controlling relative ...........................................
SCPI programming — relative ..........................................
mX+b, m/X+b (reciprocal), and logarithmic .............................
mX+b and m/X+b ...............................................................
Configuring and controlling mX+b and m/X+b .................
Logarithmic .........................................................................
SCPI programming — mX+b, m/X+b, and log ..................

5-2
5-2
5-4
5-5
5-5
5-5
5-6
5-7

Buffer and Sweeps
Buffer operations ........................................................................ 6-2
Store .................................................................................... 6-2
Recall .................................................................................. 6-2
Buffer timestamps ............................................................... 6-3
Buffer statistics ................................................................... 6-4
SCPI programming ............................................................. 6-4
Programming example ........................................................ 6-8
Voltage sweeps ........................................................................... 6-8
Overview ............................................................................. 6-8
Sweep operation ................................................................ 6-10
Recalling sweep data ........................................................ 6-10
Operating considerations .................................................. 6-10
Sweep example ................................................................. 6-11
SCPI programming — sweeps .......................................... 6-12
Programming example ...................................................... 6-15

Triggering
Trigger models ............................................................................ 7-2
Idle and initiate .................................................................... 7-4
Trigger model operation ...................................................... 7-5
Trigger model configuration — front panel ........................ 7-8
SCPI programming ................................................................... 7-10
Programming example ...................................................... 7-11
External triggering .................................................................... 7-12
Input trigger requirements ................................................. 7-12
Output trigger specifications ............................................. 7-13
External trigger example ................................................... 7-13

Limit Tests and Digital I/O
Limit testing ................................................................................ 8-2
Binning ....................................................................................... 8-5
Component handler interface .............................................. 8-7
Component handler types .................................................... 8-8
Digital output clear pattern ................................................ 8-10
Digital I/O port ......................................................................... 8-11
Sink mode — controlling external devices ....................... 8-12
Source mode — logic control ............................................ 8-14
Setting digital output lines ................................................. 8-14
SCPI programming — digital output pattern .................... 8-15
Front panel operation — limit tests .......................................... 8-16
Limit test configuration ..................................................... 8-16
Performing limit tests ........................................................ 8-17
SCPI programming — limit tests ............................................. 8-18
Programming example ...................................................... 8-21

Remote Operation
Selecting and configuring an interface ....................................... 9-2
Interfaces ............................................................................. 9-2
Languages ............................................................................ 9-2
Interface selection and configuration procedures ................ 9-3
GPIB operation and reference .................................................... 9-4
GPIB bus standards ............................................................. 9-4
GPIB bus connections ......................................................... 9-4
Primary address ................................................................... 9-6
General IEEE-488 bus commands ...................................... 9-7
Front panel GPIB operation ................................................ 9-9
Programming syntax ......................................................... 9-10
RS-232 interface reference ....................................................... 9-16
Sending and receiving data ................................................ 9-16

RS-232 settings ................................................................. 9-16
RS-232 connections .......................................................... 9-18
Error messages .................................................................. 9-19

Status Structure
Overview .................................................................................. 10-2
Clearing registers and queues ................................................... 10-4
Programming and reading registers ......................................... 10-5
Programming enable registers ........................................... 10-5
Reading registers ............................................................... 10-6
Status byte and service request (SRQ) ..................................... 10-7
Status byte register ............................................................ 10-7
Service request enable register .......................................... 10-8
Serial polling and SRQ ..................................................... 10-9
Status byte and service request commands ....................... 10-9
Status register sets .................................................................. 10-10
Register bit descriptions .................................................. 10-10
Queues .................................................................................... 10-17
Output queue ................................................................... 10-18
Error queue ..................................................................... 10-19

Common Commands
Common commands ................................................................ 11-2

SCPI Signal Oriented Measurement Commands

DISPlay, FORMat, and SYSTem
DISPlay subsystem .................................................................. 13-2
FORMat subsystem .................................................................. 13-4
SYSTem subsystem .................................................................. 13-9

SCPI Reference Tables
General notes ............................................................................ 14-2

Performance Verification
Introduction ..............................................................................
Verification test requirements ..................................................
Environmental conditions .................................................
Warm-up period ................................................................
Line power ........................................................................
Recommended test equipment .................................................
Verification limits .....................................................................

15-2
15-2
15-2
15-3
15-3
15-3
15-5

Example reading limits calculation ................................... 15-5
Calibrator voltage calculations ................................................. 15-5
Performing the verification test procedures .............................. 15-6
Test considerations ............................................................ 15-6
Restoring factory defaults ................................................. 15-6
Offset voltage calibration ......................................................... 15-7
Current measurement accuracy ................................................ 15-7
20µA-20mA range accuracy .............................................. 15-7
2nA-2µA range accuracy ................................................... 15-8
Voltage source output accuracy .............................................. 15-10

Calibration
Introduction .............................................................................. 16-2
Environmental conditions ......................................................... 16-2
Temperature and relative humidity .................................... 16-2
Warm-up period ................................................................. 16-2
Line power ......................................................................... 16-2
Calibration considerations ........................................................ 16-3
Calibration cycle ....................................................................... 16-3
Recommended calibration equipment ...................................... 16-3
Calibration errors ...................................................................... 16-4
Calibration menu ...................................................................... 16-5
Aborting calibration .................................................................. 16-6
Current calculations .................................................................. 16-6
Calibration procedure ............................................................... 16-7
Preparing for calibration .................................................... 16-7
Offset voltage calibration .................................................. 16-7
Current calibration ............................................................. 16-8
Voltage source calibration ............................................... 16-12
Entering calibration dates and saving calibration ............ 16-13
Locking out calibration ................................................... 16-14
Calibration support ................................................................. 16-14
Changing the calibration code ......................................... 16-14
Resetting the calibration code ......................................... 16-15
Displaying calibration dates ............................................ 16-15
Displaying the calibration count ..................................... 16-15

Routine Maintenance
Introduction .............................................................................. 17-2
Setting line voltage and replacing line fuse .............................. 17-2
Front panel tests ........................................................................ 17-3
DISP test ............................................................................ 17-4
KEY test ............................................................................ 17-4

Specifications

Status and Error Messages
Eliminating common SCPI errors .............................................
-113, "Undefined header" ..................................................
-410, "Query INTERRUPTED" .........................................
- 420, "Query UNTERMINATED" ....................................

B-7
B-7
B-7
B-8

DDC Emulation Commands
DDC language ........................................................................... C-2
Sweeps or A-V ohms in DDC mode ................................ C-10
Status words ..................................................................... C-11
Status byte format ............................................................ C-12

IEEE-488 Bus Overview
Introduction ............................................................................... D-2
Bus description .......................................................................... D-3
Bus lines .................................................................................... D-4
Data lines ........................................................................... D-5
Bus management lines ....................................................... D-5
Handshake lines ................................................................. D-5
Bus commands .......................................................................... D-6
Uniline commands ............................................................. D-9
Universal multiline commands .......................................... D-9
Addressed multiline commands ....................................... D-10
Address commands .......................................................... D-10
Unaddress commands ...................................................... D-10
Common commands ........................................................ D-11
SCPI commands ............................................................... D-11
Command codes ............................................................... D-11
Typical command sequences ............................................ D-12
IEEE command groups .................................................... D-13
Interface function codes .......................................................... D-14

E
IEEE-488 and SCPI
Conformance Information
Introduction ................................................................................ E-2
GPIB 488.1 Protocol .................................................................. E-3
Selecting the 488.1 protocol ....................................................... E-4
Protocol differences ................................................................... E-5
Message exchange protocol (MEP) .................................... E-5
Using SCPI-based programs ............................................... E-5
NRFD hold-off .................................................................... E-6

NDAC hold-off ...................................................................
Trigger-on-talk ...................................................................
Message available ...............................................................
General operation notes ......................................................
SRQ when buffer fills with 200 readings ...........................

E-6
E-7
E-7
E-7
E-8

Remote Calibration
Introduction ............................................................................... F-2
Calibration commands ............................................................... F-2
Remote calibration overview ..................................................... F-3

Applications Guide
Measurement considerations ..................................................... G-2
Leakage currents and guarding .......................................... G-2
Input bias current ................................................................ G-3
Voltage burden .................................................................... G-4
Noise and source impedance .............................................. G-5
Electrostatic interference and shielding ............................. G-7
Making connections ......................................................... G-10
Typical range change transients ....................................... G-12
Steps to minimize impact of range change transients ...... G-16
Zero check on / off response ............................................ G-17
Applications ............................................................................. G-18
Diode leakage current ....................................................... G-18
Capacitor leakage current ................................................. G-19
Measuring high resistance ................................................ G-19
Alternating voltage ohms measurement ........................... G-20
Cable insulation resistance ............................................... G-21
Surface insulation resistance (SIR) .................................. G-22
Photodiode characterization prior to dicing ..................... G-23
Focused ion beam applications ........................................ G-25
Using switching systems to measure multiple current sources G-26

Getting Started
•

Introduction — Description of the Model 6487 Picoammeter.

•

Overview of this manual — Provides content of this manual.

•

General information — Covers general information that includes warranty information, contact information, safety symbols and terms, and inspection.

•

Power-up — Covers line power connection, line voltage setting, fuse replacement,
power line frequency, and the power-up sequence.

•

Front panel operation — Shows the location of front panel controls, displays, and
indicators.

•

Status and error messages — Status and error messages.

•

Default settings — Covers the five instrument setup configurations available to the

user: three user defined, GPIB defaults, or factory defaults.
•

Menus — Listing of the main and configuration menu items.

•

SCPI programming — Explains how SCPI commands are presented in this
manual.

1-2

Getting Started

Model 6487 Reference Manual

Introduction
The Model 6487 is a high resolution bus-programmable (RS-232 and IEEE-488)
picoammeter. The Model 6487 has the following current measurement ranges: 8 ranges,
from 20mA down to the 2nA range. The Model 6487 also has a built-in ±500V DC voltage
source and an ohms function that includes an alternating voltage mode for enhanced high
resistance measurement accuracy.

Overview of this manual
This manual describes how to connect, program, and maintain the Model 6487
Picoammeter. The sections of the manual are organized as follows:
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–

Section 1: Getting Started
Section 2: Measurement Concepts and Connections
Section 3: Measurements and Sourcing Voltage
Section 4: Range, Units, Digits, Rate, and Filters
Section 5: Relative, mX+b, m/X+b, and log
Section 6: Buffer and Sweeps
Section 7: Triggering
Section 8: Limit Tests and Digital I/O
Section 9: Remote Operation
Section 10: Status Structure
Section 11: Common Commands
Section 12: SCPI Signal Oriented Measurement Commands
Section 13: DISPlay, FORMat, and SYSTem
Section 14: SCPI Reference Tables
Section 15: Performance Verification
Section 16: Calibration
Section 17: Routine Maintenance

Appendices to this manual contain specifications and also provide additional information
on specific topics. The appendices are organized as follows:
–
–
–
–
–
–
–

Appendix A: Specifications
Appendix B: Status and Error Messages
Appendix C: DDC Emulation Commands
Appendix D: IEEE-488 Bus Overview
Appendix E: IEEE-488 and SCPI Conformance Information
Appendix F: Remote Calibration
Appendix G: Applications Guide

Model 6487 Reference Manual

Getting Started

1-3

General information
Warranty information
Warranty information is located at the front of this manual. Should your Model 6487
require warranty service, contact the Keithley representative or authorized repair facility in
your area for further information. When returning the instrument for repair, be sure to fill
out and include the service form at the back of this manual to provide the repair facility
with the necessary information.

Contact information
Worldwide phone numbers are listed at the front of this manual. If you have any questions,
please contact your local Keithley representative or call one of our Application Engineers
at 1-800-348-3735 (U.S. and Canada only).

Safety symbols and terms
The following symbols and terms may be found on the instrument or used in this manual:
The ! symbol on an instrument indicates that the user should refer to the operating
instructions located in the manual.
The
symbol on the instrument shows that high voltage may be present on the terminal(s). Use standard safety precautions to avoid personal contact with these voltages.
The
symbol on an instrument shows that it can source or measure 1000 volts or more,
including the combined effect of normal and common mode voltages. Use standard safety
precautions to avoid personal contact with these voltages.
The WARNING heading used in this manual explains dangers that might result in personal injury or death. Always read the associated information very carefully before performing the indicated procedure.
The CAUTION heading used in this manual explains hazards that could damage the
instrument. Such damage may invalidate the warranty.

Unpacking and Inspection
Inspection for damage
The Model 6487 was carefully inspected electrically and mechanically before shipment.
After unpacking all items from the shipping carton, check for any obvious signs of physical damage that may have occurred during transit. (There may be a protective film over the
display lens, which can be removed.) Report any damage to the shipping agent immediately. Save the original packing carton for possible future shipment. Before removing the
Model 6487 from the bag, observe the following handling precautions.

1-4

Getting Started

Model 6487 Reference Manual

Handling precautions
•
•

•

Always grasp the Model 6487 by the covers.
After removing the Model 6487 from its anti-static bag, inspect it for any obvious
signs of physical damage. Report any such damage to the shipping agent
immediately.
When the Model 6487 is not installed and connected, keep the unit in its anti-static
bag and store it in the original packing carton.

Package content
The following items are included with every Model 6487 order:
•
•
•
•
•
•
•
•
•

Model 6487 Picoammeter with line cord
Protective triax Shield/Cap (CAP-31)
7078-TRX-3 Triax cable
Model 8607 1kV Source banana cable set
CS-459 4-Pin Female interlock connector
Accessories as ordered
Certificate of calibration
Model 6487 User’s Manual (P/N 6487-900-00)
Product information CD-ROM that contains PDFs of the User’s and Reference
Manuals

Reference manual
If a printed copy of the Model 6487 Reference Manual is required, order the manual package. The Keithley part number for the reference manual package is 6487-901-00. The
manual package includes an instruction manual and any pertinent addenda.

Additional references
While reading this document, you may find it helpful to consult the following documentation for reference:
Model 6487 User’s Manual — Supplied in printed form and as a PDF on the Product
Information CD-ROM included with your shipment, this manual contains basic operating
information for the user.
Low Level Measurements handbook — Keithley’s guide for effective low current, low
voltage, and high impedance measurements. Refer to www.keithley.com for more details.

Model 6487 Reference Manual

Getting Started

1-5

Power-up
Line power connection
Follow the procedure below to connect the Model 6487 to line power and turn on the
instrument.
1.

Check to see that the line voltage indicated in the window of the fuse holder assembly (Figure 1-1) is correct for the operating voltage in your area. If not, refer to the
procedure in Section 17 for setting line voltage and fuse replacement.

`^rqflk

Operating the instrument on an incorrect line voltage may cause damage to the instrument, possibly voiding the warranty.

Figure 1-1
Rear panel

MADE IN
U.S.A.

CAT I

IEEE-488

ANALOG OUT

(CHANGE IEEE ADDRESS
WITH FRONT PANEL MENU)

DIGITAL I/O

!
505V PK
505V PK
505V PK

TRIGGER LINK

INPUT

RS-232

V-SOURCE OUTPUT
505V PK TO CHASSIS

HI INTERLOCK
505V
MAX

120

FUSE

LINE

400mAT
(SB)

100 VAC
120 VAC

200mAT
(SB)

220 VAC
240 VAC

LINE RATING
50, 60Hz
50 VA MAX

Power Module

2.
3.

Before plugging in the power cord, make sure that the front panel power switch is
in the off (O) position.
Connect the female end of the supplied power cord to the AC receptacle on the rear
panel. Connect the other end of the power cord to a grounded AC outlet.

1-6

Getting Started

Model 6487 Reference Manual

t^okfkd

The power cord supplied with the Model 6487 contains a separate
ground wire for use with grounded outlets. When proper connections
are made, instrument chassis is connected to power line ground
through the ground wire in the power cord. Failure to use a grounded
outlet may result in personal injury or death due to electric shock.

Turn on the instrument by pressing the front panel power switch to the on (I)
position.

Line frequency
The Model 6487 operates at line frequencies of 50 or 60Hz. When auto detect is enabled
(factory default), line frequencies are automatically sensed and set accordingly, therefore
there are no switches to set. Use the :SYSTem:LFRequency? command (query) to read the
line frequency. The factory default setting is Auto-Detect enabled.
If the power line is noisy, auto detect may not be able to lock in on a frequency. If this
occurs, set the frequency manually. This may be accomplished using the front panel (see
the following procedure) or over the bus. Refer to Table 1-1 for commands.

Front panel procedure
1.
2.
3.
4.
5.
klqb

Press MENU.
Scroll to the LFREQ: menu item using the and RANGE keys. The present setting is displayed.
Press the cursor key.
Use the and RANGE keys to scroll to the desired menu item:
AUTOXX, 50, or 60
Press ENTER.
In the setting of AUTOXX, XX is the currently detected frequency.

SCPI programming — line frequency
Table 1-1
SCPI commands — line frequency
Command
SYSTem
:LFRequency
:AUTO
:AUTO?
[:STATE]
[:STATE]?
:LFRequency?

Description
SYSTem Subsystem:
Set power line frequency (in Hz) to 50 or 60.
Turn automatic frequency detection ON or OFF.
Read the present automatic detected line frequency
state (1 = on, 0 = off).

Read present line frequency setting.

Model 6487 Reference Manual

Getting Started

1-7

Power-up sequence
The following power-up sequence occurs when the Model 6487 is turned on:
1.

klqb

The Model 6487 performs self-tests on its EPROM and RAM with all digits and
annunciators turned on. If a failure is detected, the instrument momentarily displays an error message and the ERR annunciator turns on. Error messages are
listed in Appendix B.
If a problem develops while the instrument is under warranty, return it to
Keithley Instruments Inc., for repair.
If the instrument passes the self-tests, the firmware revision levels are displayed.
For example:
6487 A01
After the firmware revision levels are displayed, the detected line frequency is
displayed.
For example:
FREQ: 60Hz
After the detected line frequency is displayed, information on the selected remote
interface is displayed:
a. GPIB — If the GPIB is the selected interface, the instrument will display the
selected language (SCPI, 488.1, or DDC) and primary address.
Examples:
SCPI ADDR: 22
DDC ADDR: 22
b. RS-232 — If RS-232 is the selected interface, the instrument will display the
baud rate setting. For example:
RS-232: 9600b
If the FACTory setup is selected as the power-on setup, the unit is placed in the
default reading mode after the communication information is displayed. If a setup
other than FACTory is selected, the configured setup will be displayed. For example, if the USR1 setup (User Setup #1) is selected:
USING USR1
To configure power-on set up:
1. Display PWR-ON: menu, press CONFIG and then SETUP.
2. Use and RANGE keys to scroll through the menu items.
3. Press ENTER to select or EXIT to quit without changing power-on setup.

1-8

Getting Started

Model 6487 Reference Manual

Front panel operation
Figure 1-2 shows the front panel of the Model 6487. For a detailed description of the various controls, displays, and indicators, see Section 1 of the Model 6487 User’s Manual.
Figure 1-2
Front panel

6487 PICOAMMETER /VOLTAGE SOURCE
VOLTAGE
SOURCE
OPERATE

V-SOURCE
CONFIG/
LOCAL

I|Ω

MATH

FILT

ZCHK

REL

OPER

RANGE
AUTO

COMM

DISP

TRIG

LIMIT

DIGITS

RATE

RANGE

POWER
SAVE

SETUP

STORE RECALL

AZERO

DAMP

EXIT

ENTER

Status and error messages
Status and error messages are displayed momentarily. During operation and programming,
you will encounter a number of front panel messages. Typical messages are either of status
or error variety, as listed in Appendix B.
Messages, both status and error, are held in queues. For information on retrieving messages from queues, see Section 10.

Default settings
The Model 6487 can be restored to one of five setup configurations: factory default
(FACT), three user-saved (USR0, USR1, and USR2), and bus default (GPIB). As shipped
from the factory, the Model 6487 powers up to the factory default settings. Factory default
settings provide a general purpose setup for front panel operation, while the bus default
(GPIB) settings do the same for remote operation. Factory and GPIB default settings are
listed in Table 1-2.
The instrument will power up to whichever default setup was saved as the power-on setup.
klqb

At the factory, the factory default setup is saved into the USR0, USR1, and USR2
setups.

Model 6487 Reference Manual

Getting Started

1-9

Front panel setup operation
To save a user setup
1.
2.
3.
4.

Configure the Model 6487 for the desired measurement application.
Press SAVE to access the save setup menu.
Use the or RANGE key to display the desired memory location
(0 = USR0, 1 = USR1, 2 = USR2).
Press ENTER.

To restore any setup
1.
2.
3.

Press SETUP to display the restore menu:
Use the or RANGE key to display the desired setup (FACT, USR0, USR1,
USR2, or GPIB).
Press ENTER.

To select power-on setup
1.
2.
3.

Press CONFIG and then SETUP to display the power-on menu.
Use the or RANGE key to display the desired setup (FACT, USR0, USR1,
USR2, or GPIB).
Press ENTER.

Remote setup operation
Saving and restoring user setups
The *SAV and *RCL commands are used to save and recall user setups. These commands
are documented in Section 11.

Restoring factory or GPIB default setups
The SYSTem:PRESet command returns Model 6487 to the factory defaults and the
*RST command returns it to the GPIB defaults. The *RST command is documented in
Section 11 and SYSTem:PRESet is covered in Section 13.

Selecting power-on setup
The SYSTem:POSetup command is used to select which setup to return to on power-up.
The SYSTem:POSetup command is documented in Section 13.

1-10

Getting Started

Model 6487 Reference Manual

Table 1-2
Default settings
Setting
Arm Layer (CONFIG ARM):
Arm-In Source Event
Arm Count
Input Trigger Link Line
Source Bypass
Output Trigger Link Line
Output Trigger

Factory

GPIB

(:SYStem:PRESet)

(*RST)

IMM
INF
1
NEVER
2
Off

*
1
*
*
*
*

Buffer (STORE):
Count
Damping (DAMP)
Digital Filter (FILT):
Count
Type

Disabled
No effect
On
Off
10
Moving

*
*
*
*
*
*

Display Resolution (DIGITS)
Format byte order
Function
GPIB:
Address
Language

5 -digits
Swapped
Amps
No effect (On at factory)
No effect (22 at factory)
No effect (SCPI at factory)

Limit Tests:
Limit 1 and Limit 2:
HI and LO Values

Disabled
1, -1

*
*
*

Log (MATH)
Median Filter (FILT):
Rank
MX+B (MATH):
“M” Value
“B” Value
Units

OFF
Off
1
Disabled
1.0
0.0
X

*
*
*
*
*
*
*

M/X+B (MATH)
“M” Value
“B” Value
Units

Disabled
1.0
0.0
X

*
*
*
*

Ohms Mode
Range

Normal
AUTO

*
*

*
Normal
*
*
*
*

*This factory (:SYStem:PRESet) and bus (*RST) GPIB defaults are the same. Bus settings that are different
*from factory reset are as shown.

Model 6487 Reference Manual

Getting Started

1-11

Table 1-2 (cont.)
Default settings
Setting

Factory

GPIB

(:SYStem:PRESet)

(*RST)

Rate:
Slow
NPLC
6.0 (60Hz) or 5.0 (50Hz)
Rel:
Off
Rel Value (VAL)
0.0
RS-232:
No effect (Off at factory)
All Settings
No effect
Trigger Layer (CONFIG TRIG):
IMM
Trig-In Source Event
1
Trigger Count
0
Trigger Delay
1
Input Trigger Link Line
NEVER
Source Bypass
2
Output Trigger Link Line

*
*
*
*
*
*
*
*
*
*
*
*
*

Units
Voltage Source:
Operate
Amplitude
Range
Current Limit
10V Range Interlock
Sweeps:
Start Voltage
Stop Voltage
Step Voltage
Center Voltage
Span Voltage
Delay
Zero Check
Zero Correct

No effect

Off
0V
10V
25mA
Off

*
*
*
*
*

0V
10V
1V
5V
10V
1s
Enabled
Disabled

*
*
*
*
*
*
*
*

*This factory (:SYStem:PRESet) and bus (*RST) GPIB defaults are the same. Bus settings that are different
*from factory reset are as shown.

1-12

Getting Started

Model 6487 Reference Manual

Menus
Main menus
Many aspects of operation are configured through the main menus summarized in
Table 1-3. Refer to the section listed in the table for in-depth information. To access the
main menus, press the MENU key. Use the and RANGE keys to scroll through the menu
items and the and cursor keys to change options. Press ENTER to save any changes
made and leave the menu. Press EXIT to leave the menu without saving changes.
klqb

The MENU key is used to access the menu structure. However, if in remote for
IEEE-488 bus operation (REM annunciator is lit), pressing the menu key has no
effect. Press the LOCAL key to place the unit in local operation, then press the
MENU key to access the menu items.

Table 1-3
Main MENU structure
Menu item
CAL

TSTAMP
UNITS
TEST
SNUM
LFREQ

Description
Provides path to the following calibration submenu items:
VOFFSET, COUNT, RUN, VSRC-RUN, DATES, UNLOCK,
LOCK, and SAVE. See reference section for verification and
calibration information.
Timestamp format can be ABSolute or DELTa.
Readings can be displayed in ENGineering units or
SCIentific notation.
Run display or key tests.
Displays the units serial number.
Line frequency can be manually set to 50 or 60 Hz, or
AUTOmatically set. The number after AUTO indicates present
detected frequency value.

Reference
Section 15,
Section 16

Section 6
Section 6
Section 17
Section 11
“Line frequency,”
page 1-6

Model 6487 Reference Manual

Getting Started

1-13

Configuration menus
Many keys have configuration menus that allow you to configure various Model 6487
operating modes. Table 1-4 summarizes the various configuration menus available. To
access a configuration menu, press CONFIG and then the corresponding front panel key.
Table 1-4
Configuration menus
Key*

Description

Reference

I|Ω

Configure normal or alternating voltage ohms modes.

Section 3

MATH

Set up MX + B, M/X + B, and LOG math functions.

Section 5

FILT

Configure median and average filters.

Section 4

REL

Enter relative value.

Section 4

OPER

Select DC or SWEEP mode, set source amplitude and current limit.

Section 3

COMM

Configure GPIB or RS-232 interface.

Section 9

TRIG

Configure trigger parameters.

Section 7

LIMIT

Set up and enable limit tests.

Section 8

RATE

Set integration rate in number of power line cycles (NPLCs).

Section 4

SETUP

Select power-on setup.

page 9

STORE

Select number of readings to store in buffer.

Section 6

RANGE

Set upper auto range limit.

Section 4

RANGE

Set lower auto range limit.

Section 4

* Press CONFIG followed by indicated key to access configuration menu.

1-14

Getting Started

Model 6487 Reference Manual

SCPI programming
SCPI programming information is integrated with front panel operation throughout this
manual. SCPI commands are listed in tables and additional information that pertains
exclusively to remote operation is provided after each table. The SCPI tables may reference you to other sections of this manual.
klqb

Except for Section 14, most SCPI tables in this manual are abridged. That is,
they do NOT include most optional command words and query commands.
Optional command words and query commands are summarized as follows.

Optional command words
In order to be in conformance with the IEEE-488.2 and SCPI standards, the Model 6487
accepts optional command words. Any command word that is enclosed in brackets ([]) is
optional and need not be included in the program message.

Query commands
Most command words have a query form. A query command is identified by the question
mark (?) that follows the command word. A query command requests (queries) the programmed status of that command. When a query command is sent and the Model 6487 is
addressed to talk, the response message is sent to the computer.

Measurement Concepts
and Connections
•

Connection fundamentals — Covers fundamental information about connecting
test circuits to the picoammeter.

•

Basic connections to DUT — Details connecting test circuits to the picoammeter
for both current and ohms measurements.

•

Using a test fixture — Discusses using general test fixtures as well as the
Model 8009 test fixture.

•

Interlock — Covers interlock connections and operation.

•

Analog output — Covers analog output connections and discusses considerations
when using the analog output.

•

Measurement considerations — Summarizes considerations that could affect
overall measurement accuracy.

2-2

Measurement Concepts and Connections

Model 6487 Reference Manual

Connection fundamentals
The following provides important fundamental information on input connections to the
Model 6487. Typical connection drawings are provided in “Basic connections to DUT,”
page 2-4. More detailed connections for specific measurements are in Section 3.

Input connector
The rear panel INPUT connector is a 3-lug female triax connector (Figure 2-1). Make connections using a male terminated triax cable (“Low-noise input cables,” page 2-3.)
Figure 2-1
Triax input connector
CAT I

Chassis Ground

Input Low

Input High

Voltage source output connectors
The rear panel V-SOURCE OUTPUT HI and LO connectors (see Figure 1-1 in Section 1)
are used to connect the voltage source to the DUT. The voltage source is primarily used for
ohms measurements but can also be used for stand-alone source operation. See “Ohms
measurement connections,” page 2-5 and “Voltage source connections,” page 2-6 for
details.

Model 6487 Reference Manual

Measurement Concepts and Connections

2-3

Maximum input levels
The maximum input levels to the Model 6487 are summarized in Figure 2-2.
t^okfkd

The maximum safe voltage between the voltage source or ammeter
common and chassis ground (common mode voltage) is 505V peak.
Exceeding this voltage can create a shock hazard.

`^rqflk

Maximum continuous input voltage is 505V peak.

Figure 2-2
Maximum input levels
Input HI
Max Continuous
Input = 505V Peak
505V Peak

Input LO
505V Peak
Chassis Ground

Low-noise input cables
When making precision measurements, you should always use low-noise cables for
INPUT connections. The following low-noise cables are recommended for use with the
Model 6487:
Model 237-ALG-2 Triax Cable — This 2m (6.6 ft) low-noise triax cable terminated with
a 3-slot male triax connector on one end and 3 alligator clips on the other end.
Models 7078-TRX-3, 7078-TRX-10, and 7078-TRX-20 Triax Cables — These are lownoise triax cables terminated at both ends with 3-slot male triax connectors. The -3 model
is 3 ft. (0.9m) in length, the -10 model is 10 ft. (3m) in length, and the -20 model is 20 ft.
(6m) in length.
klqb

As a general rule, always use the shortest possible cable for measurements.

2-4

Measurement Concepts and Connections

Model 6487 Reference Manual

Voltage source test leads
When using the voltage source, the test leads must be rated for 505V minimum and should
include safety sheaths. These test leads are recommended for use with the Model 6487:
Model 8606 High Performance Probe Tip Kit — Consists of two spade lugs, two alligator clips, and two spring hook test probes. (The spade lugs and alligator clips are rated at
30V RMS, 42.4V peak; the test probes are rated at 1000V.) These components are
designed to be used with high performance test leads terminated with banana plugs, such
as the Model 8607 High Performance Banana Cables.
Model 8607 High Performance Banana Cables — Consists of two high voltage (1000V)
banana cables. The cables are terminated with banana plugs that have retractable sheaths.
t^okfkd

Use only test leads with a minimum rating of 505V peak for connections to the voltage source to avoid a possible shock hazard.

Basic connections to DUT
Current measurement connections
Basic connections for current measurements are shown in Figure 2-3; the DUT is the
current to be measured. Circuit high is connected to the center conductor of the input
connector and circuit low is connected to the connector’s input LO (inner shield).
Figure 2-3
Basic current measurement connections
6487

DUT
INPUT*
LO

* Maximum Continuous Input: 505V Peak

Model 6487 Reference Manual

Measurement Concepts and Connections

2-5

t^okfkd

If it is possible for the DUT or external supply to present more than
505V to the input HI, it is imperative that the connection between
input LO and the external voltage source be sufficiently low impedance
and capable of carrying the short-circuit current of the source, in order
that the LO not exceed 505V.

`^rqflk

Current limiting resistors are required for DUTs capable of forcing
voltages 505V or greater. Damage to the instrument may result if voltages greater than 505V are forced on the Model 6487 INPUT HI.

Ohms measurement connections
Basic connections for ohms measurements are shown in Figure 2-4; the DUT is the resistance to be measured. Circuit high is connected to the center conductor of the INPUT connector and circuit low is connected to the V-SOURCE OUTPUT HI terminal. Note that
INPUT LO and V-SOURCE OUTPUT LO are connected together externally.
Figure 2-4
Basic ohms connections
6487

HI
INPUT*

DUT
LO

LO
V-SOURCE OUTPUT
HI
* Maximum Continuous Input: 505V Peak.

2-6

Measurement Concepts and Connections

Model 6487 Reference Manual

Voltage source connections
Basic connections for using the voltage source independently are shown in Figure 2-5; the
DUT is the load for the voltage source. DUT high is connected to V-SOURCE OUTPUT
HI and DUT LO is connected to V-SOURCE OUTPUT LO.
`^rqflk

Do not connect external sources to the 6487 voltage source. External
sources may damage the 6487 voltage source.
Figure 2-5
Basic voltage source connections
6487

HI
HI
V-Source
Output

DUT
LO

Voltages greater than 505V
Occasionally, when making very high resistance measurements, it may be necessary to use
an external voltage source with voltages greater than the maximum tolerable input voltage
of 505V. In the event that the resistance to be measured becomes shorted or an incorrect
value of resistance is inserted in the test setup, the voltage source can permanently damage
the Model 6487. To prevent this damage, the following steps should be taken as a protection precaution.
To prevent accidental damage, a series resistor should be added to the test setup. The minimum value of this series resistor depends on the lowest current range to be used in the
measurement. If it will not be necessary to use the lower measurement ranges, a smaller
series resistor can be used, reducing the effect it will have on measurement accuracy. The
lowest necessary measurement range can be determined from the measurement range
accuracy specs, the applied voltage, and largest resistance desired to measure. If using
auto range, program the Model 6487 to not use its lowest ranges when autoranging.

Model 6487 Reference Manual

Measurement Concepts and Connections

2-7

To set the auto range lower limit from the front panel:
1.
2.
3.
4.

Press the CONFIG key.
Press the down RANGE key ( ).
Use the and RANGE keys to scroll through the available lower limit settings.
Press ENTER to save the displayed value as the lower limit. Press EXIT to return
to the previous setting.

To set the auto range lower limit over the bus, use [CURRent]:RANGe:AUTO:LLIMit
(Section 4).
Use the following formula to determine the minimum resistance for proper current limiting resistors:
– 505V-⎞ R
---------------------------------------------------------MinR series = ⎛ SourceVoltage
⎝
⎠ in
505V

Lowest range to be used

Rin

2nA or 20nA
200nA or 2μA
20μA or 200μA
2mA or 20mA

11MΩ
3.5MΩ
50kΩ
510Ω

The series limiting resistor should have a minimum power rating of:
2

MinPowerRating = SourceVoltage ⁄ R series

Example: If measuring 100GΩ resistances using an external voltage source of 750V, and
thus, a lowest necessary current range of 20nA, the minimum series resistance that will
prevent damage in the case of a shorted resistor would be:
minimum Rseries = (750V - 505V)/505V×11 MΩ = 12.25MΩ
minimum power rating = (750V)2/14MΩ =41mW
klqb

The 12.25MΩ in series will increase the measured resistance to 100.012GΩ

The Model 6487 can be programmed to calculate the resistance and subtract the series
resistance. Using the M/X+B function, in the example above, one would set M to 500, B to
-14e6, and the units character to “omega”. For more details on the M/X+B function, see
Section 5.

2-8

Measurement Concepts and Connections

Model 6487 Reference Manual

Noise and safety shields
Figure 2-6 shows typical measurement shielding. In Figure 2-6(A), a noise shield is used
to prevent unwanted signals from being induced on the picoammeter input. Amps
measurements below 1μA may benefit from effective shielding. Typically, the noise shield
is connected to picoammeter input LO. Additionally, Figure 2-6(B) shows an added safety
shield connected to earth ground and Model 6487 chassis. This type of shielding should be
used whenever hazardous voltages will be present in the test circuit.
t^okfkd

The maximum safe voltage between picoammeter LO and chassis
ground (common mode voltage) is 505V peak. The Model 6487 does
not internally limit the LO-to-chassis voltage. Exceeding 505V can create a shock hazard.
If it is possible for the DUT or external supply to present more than
505V to the input HI, it is imperative that the connection between
input LO and the external voltage source be sufficiently low impedance
and capable of carrying the short-circuit current of the source, in order
that the LO not exceed 505V.

`^rqflk

The LO to chassis breakdown voltage is 505V. Exceeding this voltage
may cause damage to the instrument.

Figure 2-6
Shielding for measurements (unguarded)

Metal Noise Shield

Chassis
Ground

DUT
INPUT

INPUT

LO
A. Noise Shield

Metal Safety
Shield

DUT
Safety
Earth
Ground

B. Safety Shield

Using a test fixture
Whenever possible, use a shielded low-leakage test fixture to make precision measurements and for safety when high voltages (>30V) are used.

Model 6487 Reference Manual

Measurement Concepts and Connections

2-9

General purpose test fixture
A general purpose test fixture is shown in Figure 2-7. This test fixture will accommodate a
variety of connection requirements.
Figure 2-7
General purpose test fixture connections
Metal Chassis

To Voltage
Source A

Insulated
Terminal
Post (6)
DUT

To 6487 B
Input
To 6487 A
COMMON

Metal Guard Plate

Banana Jacks

3-Lug Female Triax Connector

Safety
Earth
Ground

Test fixture chassis
•
•
•

The chassis of the test fixture should be metal so that it can function as a shield for
the DUT or test circuit.
The test box must have a lid that closes to prevent contact with live circuitry.
The test fixture must have a screw terminal that is used exclusively for connection
to safety earth ground.

t^okfkd

To provide protection from shock hazards, the test fixture chassis must
be properly connected to safety earth ground. A grounding wire (#18
AWG or larger) must be attached securely to the test fixture at a screw
terminal designed for safety grounding. The other end of the ground
wire must be attached to a known safety earth ground.

2-10

Measurement Concepts and Connections

Model 6487 Reference Manual

Guard plate
A metal guard plate will provide guarding or noise shielding for the DUT or test circuit. It
will also serve as a mounting panel for DUT or test circuits. The guard plate must be insulated with appropriate spacing from the chassis of the test fixture commensurate with the
external source used.

Connectors, terminals, and internal wiring
Basic connector requirements include a female triax connector and two banana jacks. The
banana jacks provide for connection to the power supply (either the internal voltage source
or an external power supply). The banana jacks must be insulated from the chassis of the
test fixture.
DUT and test circuits are to be mounted on the guard plate using insulated terminals. To
minimize leakage, select terminals that use virgin Teflon insulators.
Inside the test fixture, use an insulated wire to connect the shell of the triax connector to
the guard plate (the guard plate will serve as a noise shield).

Handling and cleaning test fixtures
Dust, body oil, solder flux, and other contaminants on connector and terminal insulators
can significantly decrease the leakage resistance resulting in excessive leakage currents.
Contaminants on DUT and test circuit components can create a leakage path. The leakage
currents may be large enough to corrupt low-level measurements.
Handling tips:
•
•
•

Do not touch the bodies of DUT or test circuit components. If you can not handle
them by their leads, use clean cotton gloves to install them in the test fixture.
Do not touch any connector or terminal insulator.
If installing a test circuit that is on a PC board, handle the board by the edges. Do not
touch any board traces or components.

Cleaning tips:
•
•

•

Use dry nitrogen gas to clean dust off connector and terminal insulators, DUT, and
other test circuit components.
If you have just built the test fixture, remove any solder flux using methanol along
with clean foam-tipped swabs or a clean soft brush. Clean the areas as explained in
the next tip.
To clean contaminated areas, use methanol and clean foam-tipped swabs. After
cleaning a large area, you may want to flush the area with methanol. Blow dry with
dry nitrogen gas.
After cleaning, the test fixture (and any other cleaned devices or test circuits)
should be allowed to dry in a 122° F (50° C) low-humidity environment for several
hours.

Model 6487 Reference Manual

Measurement Concepts and Connections

2-11

Model 8009 resistivity test fixture
This test fixture allows volume resistivity in the range from 103 to 1018¾-cm and surface
resistivity in the range from 103 to 1017¾/sq. Features include:
•
•
•

•

A 3-lug triax connector and dual binding posts make connections to the
Model 6487 simple.
Guarded electrodes that can accommodate samples up to 1/8” thick and 4” x 4”.
Safety Interlock: When properly connected to the Model 6487, the V-source goes
into a high impedance state when the test fixture’s lid is opened. Note that this
could leave a charged device in the fixture.
Screw terminal on the test fixture for safety earth ground.

For typical connections to the Model 6487, refer to Figure 2-8.
Figure 2-8
Typical connections for measurements using the Model 8009 test fixture
6517-ILC-3 Safety Interlock Cable

Model 6487

Model 8009
MADE IN
U.S.A.

CAT I
ANALOG OUT

(CHA
WITH

DIGITAL I/O

!
505V PK
505V PK
505V PK

SOURCE

TRIGGER LINK

INPUT

LID
INTERLOCK

LO
TRIAX
XXX MAX
HI/LO

RS-232

V-SOURCE OUTPUT
505V PK TO CHASSIS

HI INTERLOCK

MAX INPUT
XXXXV

505V
MAX

120

METER

FUSE

LINE

400mAT
(SB)

100 VAC
120 VAC

200mAT
(SB)

220 VAC
240 VAC

7078-TRX-3 Triax Cable

8607 Banana Plug Cables

Warning: Connect fixture ground to
safety earth ground using
safety ground wire supplied
with the test fixture.

2-12

Measurement Concepts and Connections

Model 6487 Reference Manual

Floating measurements
Figure 2-9 shows an example where the Model 6487 floats.
t^okfkd

Before attempting floating measurements, make sure to have a thorough understanding of any dangers involved. Take adequate precautions before connecting any instruments or power sources. Also, make
sure to read and understand information contained in “Connection
fundamentals,” page 2-2. Death or injury due to electrical shock can
result if adequate safety measures are not taken.
The maximum safe voltage between picoammeter LO and chassis
ground (common mode voltage) is 505V. The Model 6487 does not
internally limit the LO-to-chassis voltage. Exceeding 505V can create a
shock hazard.
If it is possible for the DUT or external supply to present more than
505V to the input HI, it is imperative that the connection between
input LO and the external voltage source be sufficiently low impedance
and capable of carrying the short-circuit current of the source, in order
that the LO not exceed 505V.

`^rqflk

Connecting COMMON or ANALOG OUT to earth while floating the
input may damage the instrument.
The LO-to-chassis breakdown voltage is 505V. Exceeding this voltage
may cause damage to the instrument.

Figure 2-9
Floating measurements

R1
R3

20V

–
R2

20V

6487
Picoammeter

Model 6487 Reference Manual

Measurement Concepts and Connections

2-13

Interlock
The Model 6487 has a built-in interlock that works in conjunction with the voltage source.
The interlock prevents the voltage source from being operated on the 50V and 500V
ranges, and optionally on the 10V range, to assure safe operation.

Interlock connections
Figure 2-10 shows interlock connections and the pin diagram of the INTERLOCK
connector. Typically, the INTERLOCK connector is connected to the same type of
connector on the test fixture. A normally open switch is connected to pins 1 and 2 of the
INTERLOCK connector as shown. When the switch is open, the interlock is asserted and
the voltage source cannot be placed in operate on the 50V or 500V voltage source ranges,
and optionally for the 10V range.
t^okfkd

If the voltage source is operating when the interlock is asserted, the
voltage source will change to a high impedance state, possibly leaving
charged DUT capacitance.

Figure 2-10
Interlock connections
Model 6487

Test Fixture

MADE IN
U.S.A.

CAT I

IEEE-488

ANALOG OUT

(CHANGE IEEE ADDRESS
WITH FRONT PANEL MENU)

DIGITAL I/O

!
505V PK
505V PK
505V PK
TRIGGER LINK

INPUT

RS-232

V-SOURCE OUTPUT
505V PK TO CHASSIS

HI INTERLOCK
505V
MAX

Interlock
Connector

120

FUSE

LINE

400mAT
(SB)

100 VAC
120 VAC

200mAT
(SB)

220 VAC
240 VAC

LINE RATING
50, 60Hz
50 VA MAX

Interlock
Connector

Interlock
Cable

Test Fixture
Pin 1

Pin 2
INTERLOCK

Normally
Open
Switch

Interlock Asserted
(Output Inhibited)
with Open Switch

2-14

Measurement Concepts and Connections

Model 6487 Reference Manual

Interlock operation
The interlock is always operational for the 50V and 500V voltage source ranges. To enable
the voltage source output, pins 1 and 2 of the INTERLOCK connector must be shorted
together. For the 10V range, the interlock is optional and can be controlled with interlock
programming (see below).

Interlock programming
Table 2-1 summarizes the commands associated with controlling the 10V range interlock
and determining if the interlock is asserted. For example, to enable the 10V range interlock, send SOURce[1]:VOLTage:INTerlock[:STATe] ON. See Section 3 and Section 14
for information on additional voltage source commands.
Table 2-1
Interlock commands
Command
SOURce[1]
:VOLTage
:INTerlock
[:STATe]
:FAIL?

Description

Default

SOURce1 Subsystem:
Interlock control:
Enable or disable 10V range interlock.1
Query if interlock is asserted:2
1 = asserted; source cannot be turned on.

OFF

1. Interlock is always enabled for 50V and 500V ranges and cannot be programmed.
2. Query can be used for all three source ranges: 10V, 50V, and 500V.

Analog output
The Model 6487 has an analog output on the rear panel. The ANALOG OUT provides a
scaled, inverting ±2V output. A full-scale reading corresponds to ±2V output.
t^okfkd

The maximum safe voltage between the voltage source or ammeter and
chassis ground (common mode voltage) is 505V DC. Exceeding this
voltage can create a shock hazard.

`^rqflk

Connecting COMMON or ANALOG OUT to earth while floating the
input may damage the instrument.

klqb

Analog outputs will be at same voltages as applied to the triax shell.

Connections for using this output are shown in Figure 2-11. For a full-scale input (i.e.
2mA on the 2mA range), the output will be -2V. Example analog outputs are listed in
Table 2-2.

Model 6487 Reference Manual

Measurement Concepts and Connections

2-15

The 2V analog output signal is not corrected during calibration. Gain errors of up to 2.5%
may appear at this output, depending on range.
The output impedance is <100¾. To minimize the effects of loading, the input impedance
of the device connected to the ANALOG OUT should be as high as possible. For example,
for a device that has an input impedance of 1M¾, the error due to loading will be approximately 0.01%. High capacitance connected to the analog output will increase the rise time.
An internal 1k¾ resistance is connected between COM and analog common for protection. The effects of this resistance on analog output accuracy are negligible.
Rel and the result of mX+b, m/X+b, or LOG have no affect on the analog output. The 2V
analog output is scaled only to the actual input.
Figure 2-11
Typical analog output connections
A. Connections

Measuring Device
(i.e. Chart recorder)

MADE IN
U.S.A.

CAT I

IEEE-488

ANALOG OUT

(CHANGE IEEE ADDRESS
WITH FRONT PANEL MENU)

DIGITAL I/O

!
505V PK
505V PK
505V PK

TRIGGER LINK

INPUT

RS-232

V-SOURCE OUTPUT
505V PK TO CHASSIS

HI INTERLOCK
505V
MAX

120

FUSE

LINE

400mAT
(SB)

100 VAC
120 VAC

200mAT
(SB)

220 VAC
240 VAC

LINE RATING
50, 60Hz
50 VA MAX

Test Lead
Model 6487 Rear Panel

B. Equivalent Circuit
* 1kΩ included for protection.
Virtually 0Ω for accuracy purposes.
Input from
Prescaler

<100Ω

Analog Output

COM
A
A

Model 6487

1kΩ∗

R L = Input Resistance of
measuring device

2-16

Measurement Concepts and Connections

Model 6487 Reference Manual

Table 2-2
Example 2V analog output values
Range

Applied signal

Analog output value (nominal)*

20nA
2mA

10.5nA
-1.65mA

-1.05V
1.65V

* Output values are within ±(2.5% + 2mV) of nominal value.

Measurement considerations
There are a variety of factors to consider when making low-level measurements. These
considerations are summarized in Table 2-3 and are detailed in Appendix G of this manual
and Appendix B of the Model 6487 User’s Manual. For comprehensive information on all
measurement considerations, refer to the Low Level Measurements handbook, which is
available from Keithley Instruments. Check www.keithley.com for more details on the
handbook.
Table 2-3
Summary of measurement considerations
Considerations
Input bias current
Voltage burden
Noise

Ground loops
Triboelectric effects
Piezoelectric and stored
charge effects
Electrochemical effects
Humidity
Light
Electrostatic interference
Magnetic fields
Electromagnetic
interference (EMI)

Description
See Appendix G for details
Offset current of Model 6487 could affect low current measurements.
Offset voltage of Model 6487 could cause errors if it is high in relation to the
voltage of the measured circuit.
Noise generated by source resistance and source capacitance.
See Model 6487 User’s Manual Appendix B for details
Multiple ground points can create error signals.
Charge currents generated in a cable by friction between a conductor and the
surrounding insulator (i.e. bending a triax cable).
Currents generated by mechanical stress on certain insulating materials.
Currents generated by the formation of chemical batteries on a circuit board
caused by ionic contamination.
Reduces insulation resistance on PC boards and test connection insulators.
Light sensitive components must be tested in a light-free environment.
Charge induced by bringing a charged object near your test circuit.
The presence of magnetic fields can generate EMF (voltage).
EMI from external sources (i.e. radio and TV transmitters) can affect sensitive
measurements.

Measurements and
Sourcing Voltage
•

Measurement overview — Explains the basic measurement and voltage source
capabilities of Model 6487.

•

Performance considerations — Covers warm-up period, voltage offset correction,
autozero, zero check, and zero correct.

•

Current measurements — Provides a basic procedure to measure current.

•

Ohms measurements — Covers methods to set up and use the ohms measurement
function.

•

Voltage source operation — Discusses configuring and using the voltage source.

•

Alternating voltage ohms mode — Discusses the alternating voltage mode that
can be used to improve accuracy and repeatability of very high resistance
measurements.

3-2

Measurements and Sourcing Voltage

Model 6487 Reference Manual

Measurement overview
Current measurements
The basic current measurement capabilities of the Model 6487 are summarized in
Table 3-1. Accuracy for each measurement function and range is listed in the specifications (Appendix A).
Table 3-1
Basic current measurement capabilities
Range

Maximum Reading

5 -Digit Resolution

2nA
20nA
200nA
2uA
20uA
200uA
2mA
20mA

±2.1nA
±21nA
±210nA
±2.1µA
±21µA
±210µA
±2.1mA
±21mA

10fA
100fA
1pA
10pA
100pA
1nA
10nA
100nA

Voltage source
The basic voltage source output capabilities of the Model 6487 are summarized in
Table 3-2. Accuracy specifications are shown in Appendix A.
Table 3-2
Basic voltage source output capabilities
Range

Maximum Output

Step Size

10V
50V
500V

±10.1V
±50.5V
±505V

200µV
1mV
10mV

Model 6487 Reference Manual

Measurements and Sourcing Voltage

3-3

Performance considerations
Warm-up period
Model 6487 can be used within one minute after it is turned on. However, the instrument
should be turned on and allowed to warm up for at least one hour before use to achieve
rated accuracy. If the instrument has been exposed to extreme temperatures, allow extra
time for the internal temperature to stabilize.

Voltage offset correction
Voltage offset correction should be performed periodically to null input amplifier offsets.
To perform correction:
1.
2.
3.
4.
5.
6.

Press the MENU key, select CAL, then press ENTER.
The unit will display the following:
CAL: VOFFSET
Press ENTER. The instrument will prompt as follows:
INPUT CAP
Connect the triax shielding cap to the INPUT jack.
Press ENTER to complete voltage offset correction.
Press EXIT to return to normal display.

To perform correction via remote, connect the triax shielding cap to the INPUT, then send
CALibration:UNPRotected:VOFFset.

Autozero
To help maintain stability and accuracy over time and changes in temperature, the
Model 6487 periodically measures internal voltages corresponding to offsets (zero) and
amplifier gains. These measurements are used in the algorithm to calculate the reading of
the input signal. This process is known as autozeroing.
When autozero is disabled, the offset and gain measurements are not performed. This
increases measurement speed up to three times. However, the zero and gain reference
points can eventually drift resulting in inaccurate readings of the input signal. It is recommended that autozero only be disabled for short periods of time.
To disable autozero from the front panel, press the AZERO button. This button toggles
autozero on and off. It can also be enabled by restoring factory or GPIB default conditions.
When autozero is enabled, a colon will be displayed after the reading.
For example:
Autozero disabled:
Autozero enabled:

0.00258 nA +00.0
0.00258 nA: +00.0

3-4

Measurements and Sourcing Voltage

Model 6487 Reference Manual

SCPI programming
Table 3-3
SCPI commands — autozero
Command
SYSTem
:AZERo
[:STATe]

Description

Default

SYSTem Subsystem:
Enable or disable autozero.

SYSTem:AZERo[:STATe]
Sending this command over the bus does not update the display while in remote. To verify
the AZERo state, send the query. The displayed autozero state will be updated when the
instrument is placed back in local.
Programming example
The following examples enable or disable the autozero feature:
SYST:AZER ON
SYST:AZER OFF
SYST:AZER?

' Enable autozero.
' Disable autozero.
' Query autozero. 1=on, 0=off

Zero check and zero correct
Zero check
When zero check is enabled (on), the input amplifier is reconfigured to shunt the input signal to low with the input impedance (Figure 3-1).
klqb

The ZCHK key toggles zero check on and off. If zero check is enabled
(“ZEROCHK” message displayed), press ZCHK to disable it.

From the front panel, enable/disable zero check by pressing the ZCHK key (ZEROCHK
message displayed). Refer to Table 3-4 for bus commands.
klqb

Leave zero check enabled when connecting or disconnecting input signals.

Figure 3-1
Equivalent input impedance with zero check enabled

Input

CIN

RIN

510Ω ||200nF .......... 2mA, 20mA
50kΩ || 2nF.............. 20mA, 200μA
3.5MΩ || 120pF ....... 200nA, 2μA
11MΩ || 100pF ........ 2nA, 20nA

Model 6487 Reference Manual

Measurements and Sourcing Voltage

3-5

Zero correct
klqb

The Model 6487 saves a single Zero Correct value (not one for each range). For
best results, acquire a new Zero Correct value after changing to the desired
range.

The Model 6487 has a zero correct feature to algebraically subtract the voltage offset term
from the measurement (to actually reduce the voltage at the input terminals, see “Voltage
offset correction,” page 3-3). Perform the following steps to algebraically zero correct the
measurement:
klqb

1.
2.
3.
4.
5.
klqb

The REL key toggles zero correct on and off if zero check is enabled
(“ZEROCCHK” message displayed). The MON annunciator turns on when zero
correct is enabled.
Enable zero check (“ZEROCHK” message displayed).
Select the range that will be used for the measurement or select the lowest range.
Press REL to enable zero correct (“ZCORRECT ON” message displayed briefly).
Press ZCHK to disable zero check.
Readings can now be taken from the display. The MON annunciator indicates that
the displayed reading is zero corrected.
With regard to the zero correct feature:
•

The Model 6487 will remain zero corrected even if it is upranged. If
downranged, re-zero the instrument.

•

The Model 6487 does not have to be re-zero corrected as long as the
ambient temperature remains stable.

•

Zero correction cancels the voltage offset term of the amplifier. With both
zero check and zero correct enabled, the instrument may not display a
perfectly zeroed reading.

•

If the Model 6487 is operating at or near TCAL, zero correction will have
very little effect. TCAL is the internal temperature of the Model 6487 when it
was last calibrated.

3-6

Measurements and Sourcing Voltage

Model 6487 Reference Manual

SCPI programming — zero check and zero correct
Table 3-4
SCPI commands — zero check and zero correct
Commands
SYSTem
:ZCHeck
[:STATe]

:ZCORrect
[:STATe]
:ACQuire
INITiate

Description

Default

SYSTem Subsystem:
Zero check:
Enable or disable zero check. When
Zero check is on, the reading on the
display is replaced with ZEROCHK.

Zero correct:
Enable or disable zero correct.
Acquire a new zero correct value.

OFF

Ref

A
B

Trigger a reading.

A) SYSTem:ZCORrect[:STATe]
This method to perform zero correction is consistent with the way it is performed from the
front panel. That is, zero correction is performed while zero check is enabled. The zero
correct state can be turned on and off repeatedly without requiring a new value. If no ACQ
has been performed since the most recent reset, zero is used for the ACQ value.

B) SYSTem:ZCORrect:ACQuire
The zero correct value can only be acquired while zero check is enabled and zero correct
state is off. The internal offset measured at that moment will become the correction value.
Zero correction can then be applied and zero check disabled. This acquire method makes it
convenient if you need to re-zero the instrument often.
klqb

Before sending a SYST:ZCOR:ACQ command, send a SYST:ZCOR:STAT OFF
command. Failure to do so means that you have a higher chance of getting a bad
Zero Correct value, particularly if your last Zero Correction was accomplished
on a different range.

Model 6487 Reference Manual

Measurements and Sourcing Voltage

3-7

The following command sequence uses the acquire method to zero correct the 200µA
range:
*RST
SYST:ZCH ON
CURR:RANG 2E-4
INIT
SYST:ZCOR:STAT OFF
SYST:ZCOR:ACQ
SYST:ZCH OFF
SYST:ZCOR ON

'
'
'
'
'
'
'
'
'

Set instrument to known default
conditions in one-shot trigger mode.
Enable zero check.
Set instrument to 200uA range.
Trigger one reading.
Turn zero correct off.
Acquire zero correct value.
Disable zero check.
Perform zero correction.

The INITiate command in the above sequence is used to trigger a reading. This reading is
the offset that is acquired as the zero correct value. See Section 7 for more information on
INITiate.
klqb

Sending the :ACQuire command while zero check is disabled will result in an
error. The command will not be executed.

Current measurements
Procedure
t^okfkd

The maximum safe voltage between picoammeter LO and chassis
ground (common mode voltage) is 505V. The Model 6487 does not
internally limit the LO to chassis voltage. Exceeding 505V can create a
shock hazard.
If it is possible for the DUT or external supply to present more than
505V to the input HI, it is imperative that the connection between
input LO and the external voltage source be sufficiently low impedance
and capable of carrying the short-circuit current of the source, in order
that the LO not exceed 505V.

`^rqflk

The LO to chassis breakdown voltage is 505V. Exceeding this voltage
may cause damage to the instrument.
The maximum input voltage and current to Model 6487 is 505V peak
and 21mA. Exceeding either of these values may cause damage to the
instrument that is not covered by the warranty.

To achieve optimum precision for low-level current measurements, input bias current and
voltage burden can be minimized by performing the offset correction procedure. Information about these offsets are provided in “Measurement considerations” on page -2.

3-8

Measurements and Sourcing Voltage

klqb

Model 6487 Reference Manual

After overloading with high voltage, it may take several minutes for the input
current to drop to within specified limits. Input current can be verified by placing the protection cap on the input connector and then use the ground link to
connect COMMON and CHASSIS ground. With the instrument on the 2nA range
and zero check disabled, allow the reading to settle until the input bias current is
within specifications. The specifications for input bias current are included in
the offset portion of the accuracy specification listed in Appendix A.

Perform the following steps to measure current:

Step 1. Select current function
Press the I | ¾ key to make sure the current function is selected.

Step 2. Enable zero check
Zero check should always be enabled before making connection changes. The ZCHK key
toggles zero check on and off. When on, the “ZEROCHK” message is displayed.

Step 3. Perform zero correction
To achieve optimum accuracy for low current measurements, it is recommended that you
zero correct the picoammeter:
•
•

Select the 2nA range (which is the lowest range).
Press the REL key so that the MON annunciator is on.

Step 4. Select a manual measurement range or enable auto range
Use the RANGE and keys to select a manual measurement range or press AUTO to
enable auto range. With auto range enabled, the instrument will automatically go to the
most sensitive range to make the measurement. See Section 4 for details on range.

Step 5. Connect the current to be measured to the picoammeter
Basic connections for measurements are shown in Figure 3-2.

Model 6487 Reference Manual

t^okfkd

klqb

Measurements and Sourcing Voltage

3-9

A safety shield is advisable whenever floating measurements are being
made (see “Floating measurements,” page 2-12). Connections for the
safety shield are shown in Figure 3-2. The metal safety shield must
completely surround the noise shield or floating test circuit and it must
be connected to safety earth ground using #18 AWG or larger wire.

When not making floating measurements, it is recommended that you ground
measurement LO at only one place in the circuit, such as with the ground link
connection on the rear panel of the Model 6487.
Fundamental information on making connections to the picoammeter input is
provided in Section 2.

Step 6. Disable zero check and take a reading from the display
If the readings are noisy, you may want to use filtering to reduce noise. Use filtering if the
noise is caused by a noisy input signal. Filtering is covered in Section 4.
Figure 3-2
Connections for amps
Red (HI)
Metal Noise Shield
Green
(Chassis)
237-ALG-2
Cable

Metal Safety Shield
Safety
Earth
Ground

Black (LO)

MADE IN
U.S.A.

CAT I

IEEE-488

ANALOG OUT

(CHANGE IEEE ADDRESS
WITH FRONT PANEL MENU)

DIGITAL I/O

!
505V PK
505V PK
505V PK

TRIGGER LINK

INPUT

RS-232

V-SOURCE OUTPUT
505V PK TO CHASSIS

HI INTERLOCK
505V
MAX

120

FUSE

LINE

400mAT
(SB)

100 VAC
120 VAC

200mAT
(SB)

220 VAC
240 VAC

Model 6487

LINE RATING
50, 60Hz
50 VA MAX

3-10

Measurements and Sourcing Voltage

Model 6487 Reference Manual

SCPI programming
Table 3-5
SCPI commands — amps function
Commands
[SENSe]
:DATA?
:FUNCtion ‘CURRent’
INITiate
READ?

Description
SENSe Subystem:
Return latest “raw” reading.
Select current function.
Trigger one or more readings.
Trigger and return reading(s).

Default

CURR

Ref
A
B
C
D

A) SENSe:DATA?
This command does not trigger a reading. It simply returns the last “raw” reading string. It
will not return the result of any instrument calculation. The reading reflects what is
applied to the input.
While Model 6487 is busy performing measurements, the :DATA? command will not
return the reading string until the instrument finishes and goes into the idle state.
klqb

The format that the reading string is returned in is set by commands in
Section 13.
If there is no reading available when :DATA? is sent, an error (-230) will occur.

B) FUNCtion ‘CURRent’
Use this command to select the current function instead of the ohms function.

C) INITiate
To return a fresh (new) reading, you can send the INITiate command to trigger one or
more readings before sending :DATA?. Details on INITiate are provided in Section 7.

D) READ?
The READ? command can be used to return “fresh” readings. This command triggers and
returns the readings. See Section 12 for details.

Model 6487 Reference Manual

Measurements and Sourcing Voltage

3-11

Programming example
The following command sequence will perform one zero corrected amps measurement:
*RST
FUNC ‘CURR’
SYST:ZCH ON
CURR:RANG 2e-9
INIT
SYST:ZCOR:STAT OFF
SYST:ZCOR:ACQ
SYST:ZCOR ON
CURR:RANG:AUTO ON
SYST:ZCH OFF
READ?

'
'
'
'
'
'
'
'
'
'
'
'
'

Return 6487 to RST defaults.
Select current function.
Enable zero check.
Select the 2nA range.
Trigger reading to be used as zero
correction.
Turn zero correct off.
Use last reading taken as zero
correct value.
Perform zero correction.
Enable auto range.
Disable zero check.
Trigger and return one reading.

Ohms measurements
Overview
To measure ohms with the Model 6487, you must set up the voltage source to the desired
range, value, and current limit (see “Voltage source operation,” page 3-15), choose an
appropriate current measurement range (or use auto range), and enable the ohms function.
With the ohms function enabled, the Model 6487 calculates the measured resistance from
the voltage source value and the measured current: R = V/I. When setting up the voltage
source, choose as high a voltage value as possible for maximum current, keeping in mind
such factors as the power dissipation and voltage coefficient of the resistance being tested.
klqb

Ohms measurements can be made using either the DC or alternating voltage
modes. See “Alternating voltage ohms mode,” page 3-21 for information on the
alternating voltage mode.

3-12

Measurements and Sourcing Voltage

Model 6487 Reference Manual

Procedure
t^okfkd

Always turn off the Model 6487 power before changing voltage source
connections to avoid a possible shock hazard.

Perform the following steps to measure resistance:

Step 1. Set up voltage source
Press either of the V-SOURCE adjustment keys, then use a manual RANGE key to set the
voltage source range. Set the voltage and current limit to the desired values using the cursor and RANGE keys.

Step 2. Perform zero correction
To achieve optimum accuracy for high resistance measurements, it is recommended that
you zero correct the picoammeter before enabling the ohms function. To do so, make sure
that zero check and the 2nA range are selected, then press the REL key to perform zero
correction. The MON annunciator will be on when zero correct is enabled.

Step 3. Select a manual current range or enable auto range
Use the manual RANGE keys to select a manual measurement range or press AUTO to
enable auto range. When using manual ranging, choose an appropriate value based on the
voltage source setting and the expected measured resistance: I = V/R.

Step 4. Connect the resistance to be measured to the picoammeter
Basic connections for ohms measurements are shown in Figure 3-3. Note that both the
picoammeter INPUT and the V-SOURCE OUTPUT jacks are connected to the resistance
under test.
t^okfkd

A safety shield is advisable whenever measurements are being made
with voltages over 30V DC. Connections for the safety shield are
shown in Figure 3-3. The metal safety shield must completely surround
the noise shield or floating test circuit and it must be connected to
safety earth ground using #18 AWG or larger wire.

Step 5. Select ohms function
Press the I|¾ key to make sure the ohms function is selected.

Step 6. Turn on voltage source
Press the OPER key to turn on the voltage source output. The VOLTAGE SOURCE
OPERATE indicator will turn on.

Model 6487 Reference Manual

Measurements and Sourcing Voltage

3-13

Step 7. Disable zero check and take a reading from the display
Press ZCHK to disable zero check and display readings. If the readings are noisy, use filtering to reduce noise.
klqb

For any ohms measurements, the ohms reading is invalid and unknown if the
voltage source is in compliance. Therefore, a value of -9.9e+36 will be returned
over the GPIB and the message I-LIMIT will be displayed on the front panel for
both normal readings and buffer recall readings for any ohms readings where
the voltage source went into compliance.

Figure 3-3
Connections for ohms measurements
Red (HI)
Metal Noise Shield
Green
(Chassis)
237-ALG-2
Cable

Metal Safety Shield

DUT

Safety
Earth
Ground

Black (LO)

DUT = Device Under Test.

V-SOURCE
OUTPUT
MADE IN
U.S.A.

CAT I

IEEE-488

ANALOG OUT

(CHANGE IEEE ADDRESS
WITH FRONT PANEL MENU)

DIGITAL I/O

!
505V PK
505V PK
505V PK

TRIGGER LINK

INPUT

RS-232

V-SOURCE OUTPUT
505V PK TO CHASSIS

HI INTERLOCK
505V
MAX

120

FUSE

LINE

400mAT
(SB)

100 VAC
120 VAC

200mAT
(SB)

220 VAC
240 VAC

Model 6487

LINE RATING
50, 60Hz
50 VA MAX

3-14

Measurements and Sourcing Voltage

Model 6487 Reference Manual

SCPI programming — ohms measurements
Table 3-6
SCPI commands — basic ohms measurements
Commands*
Measurements:
[SENSe[1]]
[:CURRent[:DC]]
:OHMS
:RANGe
:AUTO

Description

Ref

OFF

SENSe[1] subsystem:
Enable or disable ohms function.
Select manual current range (-0.021 to 0.021A).
Enable or disable auto current range.

Sourcing voltage:
SOURce[1]
SOURce[1] subsystem:
:VOLTage
Voltage source commands:
[:LEVel]
[:IMMediate]
[:AMPLitude]
Set output voltage (-505V to +505V).
:RANGe
Set voltage source range (10, 50, or 500).
:ILIMit
Set current limit (25μA, 250μA, 2.5mA, or 25mA).
:STATe
Turn voltage source output on or off.
READ?

Default

0V
10V
25mA
OFF

Trigger and return reading(s).

* Zero correct and zero check commands not included. See Table 3-4.

A) [SENSe[1]][:CURRent[:DC]]:OHMS
Use this command to turn the ohms function on or off. When the ohms function is enabled,
the Model 6487 calculates the reading from the measured current and the voltage source
setting: R = V/I. Additional OHMS commands control the alternate voltage ohms mode as
described in “Alternating voltage ohms mode,” page 3-21.

B) SOURce[1]:VOLTage
These commands select the voltage source range, set the source level and current limit,
and turn the source output on and off. Additional voltage source commands control voltage sweeps (see Section 6).

Model 6487 Reference Manual

Measurements and Sourcing Voltage

3-15

Programming example — ohms measurements
The following command sequence will perform one zero-corrected resistance
measurement:
*RST
FORM:ELEM READ,UNIT
SYST:ZCH ON
RANG 2e-9
INIT
SYST:ZCOR:ACQ
SYST:ZCOR ON
RANG:AUTO ON
SOUR:VOLT:RANG 10
SOUR:VOLT 10
SOUR:VOLT:ILIM 2.5e-3
SENS:OHMS ON
SOUR:VOLT:STAT ON
SYST:ZCH OFF
READ?

'
'
'
'
'
'
'
'
'
'
'
'
'
'
'
'
'

Return 6487 to GPIB defaults.
Measurement, units elements only.
Enable zero check.
Select the 2nA range.
Trigger reading to be used as zero
correction.
Use last reading taken as zero
correct value.
Perform zero correction.
Enable auto current range.
Select 10V source range.
Set voltage source output to 10V.
Set current limit to 2.5mA.
Enable ohms function.
Put voltage source in operate.
Disable zero check.
Trigger and return one reading.

Voltage source operation
Voltage source edit keys
The V-SOURCE and keys will operate in the same manner as the RANGE and keys if
they are not being used to change the voltage source values. The AUTO key acts as a
shortcut to set the V-SOURCE to 0V.

Configuring the voltage source
To set up the voltage source:
1.
2.
3.

Press CONFIG then OPER.
Select either the DC mode for normal operation or SWEEP for voltage sweeps (see
Section 6 for details on sweeps). Press ENTER.
After the mode is selected, the reading disappears and is replaced with a fullresolution value of the voltage source with the left-most position highlighted for
editing.
Use the RANGE and arrows to change the voltage source range and indicate the
range selected (10V, 50V, or 500V).

3-16

Measurements and Sourcing Voltage

Model 6487 Reference Manual

Enter the desired voltage source value, then press ENTER. Voltage values are
changed immediately from this configuration by pressing the arrow keys. The and
arrows are used to select the digit being edited and the V-SOURCE and keys
change the value. The digits will not increment beyond the limit for the present
source range with subsequent source arrow key presses.

klqb

The V-SOURCE and keys will operate in the same manner as the RANGE
and keys if they are not being used to change the voltage source values.

After the voltage value and range is selected, press ENTER to advance to the current limit display and select the desired current limit. The current limit display
offers different choices depending on the source range (Table 3-7). Pressing
ENTER or EXIT from this display returns you to the normal readings display.

Table 3-7
Voltage source current limits
Source Range:

Selectable Current Limit

10.0000V Range

25µA

250µA

2.5mA

50.000V Range

25µA

250µA

2.5mA

500.00V Range

25µA

250µA

2.5mA

25mA

Sourcing voltage
t^okfkd

Always turn off the Model 6487 power before changing voltage source
connections to avoid a possible shock hazard.

Perform the following steps to source voltage:

Model 6487 Reference Manual

Measurements and Sourcing Voltage

3-17

Step 2. Connect the load to the source output
Basic connections for sourcing voltage are shown in Figure 3-4.
t^okfkd

A safety shield is advisable whenever measurements are being made
with voltages over 30V DC. Connections for the safety shield are
shown in Figure 3-4. The metal safety shield must completely surround
the noise shield or floating test circuit and it must be connected to
safety earth ground using #18 AWG or larger wire.

Step 3. Turn on voltage source
Press the OPER key to turn on the voltage source output. The VOLTAGE SOURCE
OPERATE indicator will turn on.
`^rqflk

Do not connect external sources to the 6487 voltage source. External
sources may damage the 6487 voltage source.

Figure 3-4
Connections for sourcing voltage

Metal Safety Shield
Load

Safety
Earth
Ground
V-SOURCE
OUTPUT
MADE IN
U.S.A.

CAT I

IEEE-488

ANALOG OUT

(CHANGE IEEE ADDRESS
WITH FRONT PANEL MENU)

DIGITAL I/O

!
505V PK
505V PK
505V PK
TRIGGER LINK

INPUT

RS-232

V-SOURCE OUTPUT
505V PK TO CHASSIS

HI INTERLOCK
505V
MAX

120

FUSE

LINE

400mAT
(SB)

100 VAC
120 VAC

200mAT
(SB)

220 VAC
240 VAC

Model 6487

LINE RATING
50, 60Hz
50 VA MAX

3-18

Measurements and Sourcing Voltage

Model 6487 Reference Manual

Operate considerations
OPER (operate) key
The OPER (operate) key will function to turn the voltage source off, even if the instrument
is operating under remote control (REM annunciator on), assuming that the LLO (Local
Lockout) function has not been employed. While in remote, the OPER key will only turn
the source off. To turn it on, the Model 6487 must be in local (see Section 9).

Voltage source off state
The voltage source is not in a high-impedance state when it is turned off. Rather, it is in a
state that acts just like the voltage source was programmed to 0V on the selected range. It
will enter this state on power-up after the VOLTAGE SOURCE OPERATE light blinks. In
contrast, the safety interlock will cause the voltage source to go into a high-impedance
state instead of 0V output and the source will stay in the high-impedance state until the
operate state is changed to on. The exception is the 10V range where the interlock is
optional. The OPERATE light and front panel display do not indicate the difference
between 0V output and high-impedance output caused by an open interlock. The interlock
status is available by query via remote (see Table 3-8).

Compliance indication
At any time, it is possible that the voltage source will go into compliance (current limit
reached). Should this situation occur, the OCOMP annunciator (Output Compliance) will
flash and the displayed voltage value for readings of less than 6 digits will alternate
between showing the value and displaying “CMPL”. If you are in a menu where the voltage source value is not shown on the right-most four characters of the display, only the
flashing OCOMP annunciator will be shown.

Open interlock indication
If the interlock is asserted (opened) while the unit is on 50 or 500V range, the voltage
source will also technically be in compliance. However, there will be no indication of that
status over the front panel or in the status registers (Section 10). The open interlock takes
precedence.

Model 6487 Reference Manual

Measurements and Sourcing Voltage

3-19

SCPI commands — voltage source
Table 3-8
SCPI commands — voltage source
Commands
SOURce[1]
:VOLTage
[:LEVel]
[:IMMediate]
[:AMPLitude]
:RANGe
:ILIMit
:STATe
:INTerlock
:FAIL?

Description

Default

Ref

0V
10V
25mA
OFF
OFF

A
B
C
D
E

SOURce[1] subsystem:
Voltage source commands:

Set output voltage level (-505V to +505V).
Set voltage source range (10, 50, or 500V).
Set current limit (25μA, 250μA, 2.5mA, or 25mA).1
Turn voltage source output on or off.
Enable or disable interlock for 10V range.2
Query interlock state (1 = asserted, and source
output cannot be turned on).

1. 25mA not available for 50V and 500V ranges.
2. See Section 2 for interlock operation.

A) [:LEVel] [:IMMediate] [:AMPLitude]
Use this command to set the voltage source output level from -505V to 505V. Note that if
the STATe is on, then the voltage will change as soon as this command is processed. Sending a value outside of the present range will generate Error -222 “Parameter Out of
Range”. To go to a higher value, you must first change the source range.

B) RANGe
This command selects the range: 10V, 50V, or 500V. If you choose a range lower than the
present level, the level will be changed to the maximum value for that range. The range
selected will be the one that best accommodates the value sent. A value of 10.01, for
example, will select the 50V range.

C) ILIMit
Use this command to set the voltage source current limit to 25μA, 250μA, 2.5mA, or
25mA. Note, however, that the maximum current limit for the 50V and 500V ranges is
2.5mA.

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Measurements and Sourcing Voltage

Model 6487 Reference Manual

D) STATe
This command turns the voltage source output on or off. However, the voltage source output cannot be turned on if the interlock is asserted. When the voltage source is turned off,
the source will be a low-impedance 0V source (limited to approximately 1mA) and will
discharge small capacitances (DUT, cables, etc.).

INTerlock

These commands control the interlock for the 10V range and query whether or not the
interlock is asserted. Note that for the 50 and 500V ranges, this setting is ignored since the
interlock is directly tied to the hardware and cannot be bypassed. Therefore, this command
has no effect when the source is on any range other than the 10V range. Attempting to turn
off the interlock state while on the 50 or 500V ranges will generate a -221 “Settings Conflict” error. Upranging from the 10V range will always cause the interlock to be enabled.
When you range back down to the 10V range, the interlock state will be reset to what it
was when you left the 10V range. See Section 2 for more interlock information.
t^okfkd

When the interlock is asserted, the voltage source will change to a
high-impedance state. This situation could leave any connected device
charged to the last programmed voltage.

Programming example — voltage
The following command sequence will output 5V on the 10V range with a 2.5mA limit:
*RST
SOUR:VOLT:RANG 10
SOUR:VOLT 5
SOUR:VOLT:ILIM 2.5e-3
SOUR:VOLT:STAT ON

'
'
'
'
'

Return 6487 to GPIB defaults.
Select 10V source range.
Set voltage source output to 5.
Set current limit to 2.5mA.
Put voltage source in operate.

Model 6487 Reference Manual

Measurements and Sourcing Voltage

3-21

Alternating voltage ohms mode
Overview
Ohms can be measured in one of two ways: DC (normal) or alternating voltage (A-V). The
alternating voltage ohms method is especially useful when the resistance or device being
measured exhibits high background currents or high noise currents. These are typical
problems seen when measuring high resistances, devices with moderate to high capacitance, or when adequate shielding is unavailable. By measuring current differences caused
by a change in applied voltage, the alternating voltage method greatly reduces effects of
currents that are not caused by the applied voltage, i.e., not resistive current. The A-V
mode consists of switching the source level between 0V and a user-selected value
(Figure 3-5). During each phase, one or several readings are collected into separate buffers
for that phase, designated V-High and V-Zero. A third buffer is created by subtracting the
n-th reading of the V-Zero buffer from its counterpart in the V-High buffer and storing
these differences in a buffer designated V-Delta. Both from the front panel and via remote,
A-V ohms readings always come from the V-Delta buffer.
The purpose of the alternating voltage ohms mode is to improve the accuracy and
repeatability of very high resistance measurements, which are subject to errors from
background currents in the test setup. By taking two current measurements, one at a
specific step voltage and a second at 0V, these background currents can be largely nulled
out and the resistance calculated from the source voltage and measured current is closer to
the actual DUT resistance. Data stored in the buffer can also be averaged to improve
repeatability.
Key test parameters for A-V ohms include the step voltage, measurement time, and the
number of test cycles. The optimum step voltage value depends on the measured resistance and desired current. The measurement time must be carefully chosen to assure adequate settling during both the step-voltage (V-High) and 0V (V-Zero) phases of the
measurement. The number of cycles to measure and average is often a compromise
between improvement in repeatability and the overall measurement time.
Figure 3-5
Alternating voltage ohms
One Cycle

Time
V-High

V-Zero (0V)

Time

3-22

Measurements and Sourcing Voltage

Model 6487 Reference Manual

Figure 3-6 shows a comparison of the A-V voltage and the resulting current. When the
voltage first makes a transition from low to high or high to low, the current initially
increases to maximum and then decays to its quiescent value. The decay period, of course,
depends on the RC time constant (τ) of the circuit being tested.
Figure 3-7 demonstrates the clear advantages of A-V ohms. The decaying curve shows
how current decays time without averaging, while the steady-steady current plot at the bottom shows substantially improved results due to averaging of the A-V readings.
Figure 3-6
A-V voltage and current

Current

Voltage

Figure 3-7
Averaged A-V current
18
15
12
With Averaging

Current
(nA)

9
Without
Averaging

6
3
1
0
0

Time (s)

Model 6487 Reference Manual

Measurements and Sourcing Voltage

3-23

Storing A-V ohms readings
Follow the steps below to setup and use the A-V ohms mode. Refer to Table 3-9 for A-V
ohms configuration menu items.
klqb

The following procedure assumes the Model 6487 is connected to the DUT. See
Figure 3-3 and Section 2 for details on ohms connections.

klqb

Before starting the configuration process for A-V ohms, make sure the 6487 is
on a current measurement range high enough to not overflow with the applied VHI value. Autorange is turned off while A-V ohms is running.

Table 3-9
A-V ohms menu selections
Menu Item
V-HI

Description

Default

High source voltage value (-505 to 505V).

10V

TIME

Time for each A-V phase.

15s*

ONE-SHOT

Enable (YES) or disable (NO) one shot mode (one reading per phase).

YES

CYCLES

Number of A-V cycles (one high and low step): 1 to 9999.

AUTOCLEAR

Enable (Y) or disable (N) buffer auto clear with A-V ohms.

* Default depends on integration time when entering A-V ohms menu: 15s for 1 PLC or greater, 1s for 0.1 PLC, and 0.1s for 0.02 PLC.

1.
2.

Press CONFIG then I | ¾ to access the ohms configuration menu.
Select ALT-VOL, then press ENTER. The unit will prompt for the high voltage
value:
V-HI:+10.0000
If you have “regular” readings in the buffer, you will be prompted to clear the
buffer. Use CONFIG → STOR 0000 RDGs → ENTER to clear
Enter the desired high voltage level, then press ENTER. The unit will prompt for
the time that the voltage source value will be at each phase in the A-V cycle:
TIME: 15.00 s
Enter the desired time, then press ENTER. The Model 6487 will prompt for the
one-shot mode:
ONE-SHOT: YES
Select either YES to enable the one-shot mode (taking only one current measurement at the end of each phase) or NO to disable the one-shot mode (taking current
measurements continuously during each phase, which will result in a difference
buffer of many points, detailing the step response of the DUT), then press ENTER.
The unit will prompt for the number of A-V cycles:
CYCLES: 0003

3-24

Measurements and Sourcing Voltage

7.
8.
9.

klqb

Model 6487 Reference Manual

Set the desired number of A-V cycles, then press ENTER. The unit will prompt
you as to whether or not you wish to clear the buffer automatically when a new
A-V measurement is started:
AUTOCLEAR: Y
Select Y or N as desired, then press ENTER.
At this point, the voltage source is in operate at 0V and the unit displays the
message TRIG TO STRT.
To start storing A-V ohms readings, press the TRIG key. The asterisk (*) character
will turn on to indicate the A-V readings are being stored. It will turn off when
storage is complete.
To halt the A-V process, press the EXIT key once. The voltage source turns off
and the I|¾ TO REARM message will display. A second press of the EXIT key
takes you back to the normal reading display. From this reading display, you can
still press the I|¾ once and the A-V ohms sequence will again be armed.
Alternatively from this reading display, press CONFIG → I|¾ and change the
selection back to NORMAL to take regular (not A-V) ohms readings.
Pressing the EXIT or OPER key while A-V ohms is in progress will cause the
message I|¾ TO REARM to appear.

Recalling A-V ohms readings
Over the front panel, you can view both amps and ohms A-V readings during the recall
process. To do so, press the RECALL key, then use the and cursor keys to cycle among
amps, ohms, voltage source, and time values for each reading. Use the RANGE and
keys to cycle through individual readings or buffer statistics, which are calculated on the
basis of the amps readings (see Figure 3-8 for recall sequence).
Note that the maximum current will result in a minimum ohms reading and vice-versa.
The MIN reading applies to the minimum current (maximum ohms), while the MAX reading applies to the maximum current (minimum ohms).
Expressing the standard deviation in ohms is not meaningful; therefore it cannot be
viewed in ohms and will always show a blank (“---------”). The same applies for the Pk-Pk
display. Average will be converted to ohms.

Model 6487 Reference Manual

Measurements and Sourcing Voltage

3-25

Buffer Statistics

Amps

*Maximum current will result in minimum ohms and vice-versa.
The MIN value applies to the minimum amps (maximum ohms) reading.
The MAX value applies to the maximum amps (minimum ohms) reading.

Ohms

▲

Reading Value (Ohms)
Reading Value (Ohms)
Reading Value (Ohms)
Reading Value (Ohms)
Reading Value (Ohms)
Reading Value (Ohms)
Reading Value (Ohms)
Reading Value (Ohms)
Reading Value (Ohms)
Reading Value (Ohms)
---------------------------Minimum Value (Ohms)*
Maximum Value (Ohms)*

▲

XX
XX

Reading Value (Amps)
Reading Value (Amps)
Reading Value (Amps)
Reading Value (Amps)
Reading Value (Amps)
Reading Value (Amps)
Reading Value (Amps)
Reading Value (Amps)
Reading Value (Amps)
Readingg Value (Amps)
p
Standard Deviation Value
Average Value
Peak to Peak Value
Minimum Value (Amps)*
Maximum Value (Amps)*

▲

RANGE

10
9
8
7
6
5
4
3
2
1

▲

RANGE

RDG
NO.
RDG
NO.
RDG
NO.
RDG
NO.
RDG
NO.
RDG
NO.
RDG
NO.
RDG
NO.
RDG
NO.
RDG
NO.
STD
DEV
AVERAGE
PK-PK
MIN
AT
MAX
AT

▲

Figure 3-8
A-V ohms reading recall sequence

Vsource
Vsource
Vsource
Vsource
Vsource
Vsource
Vsource
Vsource
Vsource
Vsource
---------------------------Vsource
Vsource

Timestamp
Timestamp
Timestamp
Timestamp
Timestamp
Timestamp
Timestamp
Timestamp
Timestamp
Timestamp
Timestamp
---------------------------Timestamp
Timestamp

Voltage Source

Buffer
Timestamps

Operating considerations
Range
Auto range cannot be used with A-V ohms. Auto range will be automatically disabled
when arming A-V ohms from the front panel. Over the GPIB, however, sending the
CURR:OHMS:AVOL:ARM command with auto range on will result in error +852 “No
A-V ohms with Autorange”. Also, only the following ranges can be used: 20nA, 2µA,
200µA, and 20mA. If on any other range, the unit will uprange to the closest allowed range.

Filtering
The median and average filters are not used in the A-V ohms mode. Once the A-V ohms
process is complete, the state of the filters will be restored.

Rate and autozero
During A-V ohms, integration rates are restricted to either 0.02 PLC, 0.1 PLC, 1 PLC, 6 PLC,
or 60 PLC. Autozero is turned off but restored after completion if it was previously on. If the
integration rate is set to any other value, it will be set to the closest of these settings. However,
the original integration rate will not be restored at the conclusion of the A-V ohms cycle.
Integration times of 0.02 PLC and 0.1 PLC will automatically cause the display to be disabled during the A-V ohms run. After the desired number of cycles has completed (or an
OHMS:AVOL:ABORt command is received), the display will be restored.

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Model 6487 Reference Manual

Triggering considerations
When A-V ohms is selected, the ARM-IN trigger source is forced to TIMER and the time
interval selected will be slightly higher than that required for the A/D integration. For
example, at 1 PLC the integration time is 16.67 msec, so sending the OHM:AVOL:ARM
command will set the ARM-IN timer interval to 18 msec. (The detailed table is below.)
Likewise, the ARM-IN count will be set to INFinite. When exiting A-V ohms with an
AVOL:OHMS:ABOR command or when the desired number of cycles has completed, the
previous trigger model settings will be restored. See Section 7 for additional triggering
information.
PLC
0.02
0.1
1
5 (50Hz)
6 (60Hz)
50 (50Hz)
60 (60Hz)

50Hz measurement interval
(milliseconds)
0002
0004
0022
0102

60Hz measurement interval
(milliseconds)
0002
0004
0018
0102

1002

Trigger state after A/V ohms
Once an A-V ohms reading sequence has been completed, the instrument will be left in the
trigger IDLE state. If you are operating remotely (GPIB or RS-232), over the front panel,
normal readings will resume after completing A-V ohms (although the “I/¾ TO REARM”
message will obscure these readings untill you press EXIT). Send an INIT:IMM command
to resume taking readings. See Section 7 for more triggering information.

Normal ohms with A-V ohms
Normal ohms (SENS:OHMS:STAT) is not compatible with A-V ohms since the latter
relies on differences between current measurements in time. Therefore, the I | ¾ key is
ignored and the SENS:OHMS:STAT command is rejected with an error +850 “Not
Allowed with A-V Ohms” while A-V ohms is armed.

Buffer operation
The same memory space is used for the regular 3,000 point buffer as for the three A-V
ohms buffers. If there are already readings in the buffer, attempting to arm A-V ohms readings results in a -225 “Out of Memory” error. To avoid inadvertently writing over any
desired readings, either send a TRAC:CLEar command over the bus or attempt to store 0
readings to manually clear the buffer from the front panel. From the front panel, attempting to select A-V ohms from the CONFIG -> OHMS menu will generate the message
“CLEAR BUFFER” if there are already readings in the buffer.
The converse also applies if you have collected some A-V ohms readings and then press
the STORE key. If the buffer has stored A-V ohms readings, you will be given the
“CLEAR BUFFER” prompt so that you do not inadvertently write over the A-V ohms

Model 6487 Reference Manual

Measurements and Sourcing Voltage

3-27

data you have collected (easy to do, since STORE is located right next to RECALL).
When working remotely, sending the TRAC:FEED:CONT NEXT command while there
are A-V ohms readings in the buffer will result in a -225 “Out of Memory” error. Send
TRAC:CLEar to clear out the buffer before attempting to store buffer readings.

Command restrictions
When A-V ohms is running, the following commands are locked out. Attempting any of
them returns error +850 “Not Allowed with A-V Ohms.”
SENS:CURR:DC:MED:STAT
SENS:CURR:DC:MED:RANK
SENS:CURR:DC:AVER:TCON
SENS:CURR:OHMS:STAT
SENS:CURR:DC:NPLC
SENS:CURR:DC:RANG
SENS:CURR:DC:RANG:AUTO
SOUR:VOLT[:LEV][:IMM][:AMPL]
SOUR:VOLT:STATe
SOUR:VOLT:RANGe
TRAC:FEED
TRAC:FEED:CONT
TRAC:POIN
TRAC:TST:FORM
TRAC:DATA?
SYST:AZER:STAT
DISP:ENAB
Tight timing is crucial to getting reliable results with A-V ohms. Anything that changes
the timing between readings would make it impossible to continue averaging in with any
previously collected readings. Therefore, the following command is locked out from the
GPIB while A-V ohms readings are present in the buffer. You must first clear the buffer
with TRAC:CLEar, otherwise an error +851 “Not allowed with A-V Ohms buffer” will be
generated.
SENS:CURR:DC:NPLC
Over the front panel, pressing any key (for example RATE) that would change one of the
settings associated with this command will automatically cause the buffer to be cleared if
the following conditions are true:
•
•
•

There are A-V ohms readings present in the buffer.
SENS:CURR:OHMS:AVOL:CLE:AUTO is set to OFF.
The front panel ohms mode is set for ALT-VOL.

If the buffer is cleared by one of these key presses, a “BUF CLEARED” message will be
displayed. Regardless of whether the buffer gets cleared by the key press (it does not, for
instance, if the OHMS:AVOL:CLE:AUTO setting is true), you also will have to re-enter
the CONFIG-> I | Ω menu to select a new time interval before making another A-V ohms
run from the front panel.

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Model 6487 Reference Manual

Interlock
Attempting to run A-V ohms from the front panel while the interlock is open and failing
will result in the error message “CLOSE INTLCK” being displayed. If trying to run
remotely with the :ARM command the error event +802 “Output Blocked by Interlock” is
generated.

SCPI commands — A-V ohms
Table 3-10
SCPI commands — A-V ohms
Commands

Description

Default

Ref

To make measurements:
[SENSe[1]]
SENSe[1] subsystem:
[:CURRent[:DC]]
Current measurement commands:
:OHMS
Ohms mode commands:
:AVOLtage
Path to A-V ohms commands:
[:ARM]
Arm A-V ohms mode.
[:ARM]?
Query if A-V ohms is armed. (1 = armed).
:ABORt
Abort A-V ohms mode.
:VOLTage
Set high voltage value (-505 to 505V).
:TIME
Set time interval for each phase.
:POINts?
Query number of points.
:ONEShot
Enable or disable one-shot mode.
:CYCLes
Set number of A-V cycles (1 to 9999).
:UNITs
Select AMPS or OHMS units.
:CLEar
Clear A-V ohms buffer.
:AUTO
Enable/disable A-V buffer auto clear.
:BCOunt?
Query number of A-V points.

10V
15s*
ON
3
AMPS
ON

A
A
B
C
D
E
F
G
H
I
I
J

To access A/V readings:
TRACe
:DATA? [BUFFER]
:MODE?
CALCulate3
:FORMat
:DATA?

TRACe subsystem:
Request data from BUFFER.
Query buffer mode: DC or AVOLtage.
CALCulate3 Subsystem:
Select buffer statistic; MINimum, MAXimum,
MEAN, SDEViation, or PKPK.
Read the selected buffer statistic.

*Default depends on integration rate: 15s for 1 PLC or greater, 1s for 0.1 PLC, and 0.1s for 0.02 PLC.

BUFFER

K
L

MEAN

Section 6

Model 6487 Reference Manual

Measurements and Sourcing Voltage

3-29

A) OHMS:AVOLtage[:ARM]
This command arms the A-V ohms mode. Once this command is sent, the next INIT command starts A-V readings. Sending this command, if there are normal readings in the
buffer, results in error -225 “Out of Memory”. Use TRAC:CLEar to clear out the buffer. If
there are A-V ohms readings in the A-V buffers, this command will automatically clear
those buffers in preparation for the next run if the OHMS:AVOL:CLEar:AUTO state is
true. Note that ARMing the A-V ohms mode will also set the source value to zero and turn
operate on. The ARM command is not allowed if the picoammeter is in auto range
(CURR:RANG:AUTO ON); attempting to send the ARM command if autoranging results
in error +852 “No A-V ohms with Autorange”. If the combination of integration time and
programmed TIME interval would result in more than the maximum 1,000 readings per
phase, error +853 “Too Many A-V Ohms Readings” is returned.
The :ARM? query returns a “1” if A-V ohms has been armed even if the unit is still in the
idle state (See Section 7).
klqb

We strongly recommend that no commands except for the INIT be sent after
sending the OHMS:AVOL:ARM command.

B) OHMS:AVOLtage:ABORt
This command closes the A-V buffer and resets the source value back to 0V. The source is
also placed in standby.

C) OHMS:AVOLtage:VOLTage
This command sets the positive voltage. During each A-V cycle, the voltage source level
alternates between 0V and this programmed value.

D) OHMS:AVOLtage:TIME
This command sets the time interval in seconds that the source will be in each phase. The
number of readings collected per phase will be determined by the integration period and
trigger delay, if any. Note that changing the time will clear out any A-V buffer data that
has been collected regardless of whether CLEar:AUTO is enabled or not. Sending a time
value that would result in more than the maximum of 1000 readings per phase based on
the present integration time will result in error +853 “Too Many A-V Ohms Readings”.
The default time interval depends on the integration time selected.
60Hz
Time (milliseconds)

0.02 PLC

0.1 PLC

1 PLC

6 PLC

60 PLC

102

1002

0.02 PLC

0.1 PLC

1 PLC

5 PLC

50 PLC

102

1002

50Hz
Time (milliseconds)

3-30

Measurements and Sourcing Voltage

Model 6487 Reference Manual

OHMS:AVOLtage:POINts?

This query returns the number of points per phase based on the user-supplied TIME value
above. If the number of points would be greater than the maximum of 1,000 (for example,
if you had set a new integration rate but not yet changed the AVOL:TIME value), then
-999 will be returned. A -999 return value indicates that you cannot send the
OHMS:AVOL:ARM command until you adjust either the time interval or the integration
rate to obtain a valid number of points.

OHMS:AVOLtage:ONEShot

This command controls the one-shot A-V ohms mode. If the one-shot mode is ON, then
only a single reading is collected for each voltage phase at the end of the TIME interval
given above.

G) OHMS:AVOLtage:CYCLes
This command sets the number of cycles to run A-V ohms. A cycle is defined as one
V-High and one V-Zero step.

H) OHMS:AVOLtage:UNITs
This command sets the units that the A-V ohms readings will be stored and returned in,
amps or ohms.

OHMS:AVOLtage:CLEar

CLE manually clears the A-V ohms buffers. TRAC:CLEar will also do the same thing.
AUTO ON enables A-V ohms auto-clear. If enabled, arming the next A-V ohms run will
clear out the buffers. If disabled, subsequent A-V ohms runs will get averaged in with the
saved readings.

OHMS:AVOLtage:BCOunt?

This query returns the number of V-High/V-Low cycles that have been averaged to result
in the data stored in the A-V ohms buffer.

K) TRACe:DATA? [BUFFER]
This query returns data either from the normal buffer or the A-V ohms buffer. If A-V ohms
is not on and no A-V ohms readings have been collected, normal buffer readings will be
returned. If A-V ohms readings have been collected, A-V ohms readings will be returned.

TRACe:MODE?

This query returns the type of data stored in the buffer (either DC or AVOLtage).

Model 6487 Reference Manual

Measurements and Sourcing Voltage

3-31

Programming example — A-V ohms measurements
The following command sequence will perform A-V ohms measurements with a 5V high
value, 10s per phase, and 5 A-V cycles:
*RST
TRAC:CLE
RANG 20e-3
OHMS:AVOL:VOLT 5
OHMS:AVOL:ONES OFF
OHMS:AVOL:CLE:AUTO ON
OHMS:AVOL:TIME 10
OHMS:AVOL:CYCL 5
OHMS:AVOL:UNIT OHMS
SYST:ZCH OFF
OHMS:AVOL:ARM
INIT

TRAC:DATA?

'
'
'
'
'
'
'
'
'
'
'
'
'
'
'
'

Return 6487 to GPIB defaults.
Clear buffer of all readings.
Select 20mA range (turn off auto).
Set high voltage to 5V.
Disable one-shot mode.
Enable buffer auto clear.
Set time per phase to 10s. (A)
Set number of A-V cycles to 5. (B)
Select ohms units.
Disable zero check.
Arm A-V ohms, turn on source.
Trigger A-V readings.
Wait for time [(A) × 2] × cycles (B)
before requesting readings. 100s in
this example.
Request data from A-V ohms buffer.

Range, Units, Digits,
Rate, and Filters
•

Range, units, and digits — Provides details on measurement range, reading units,
and display resolution selection. Includes the SCPI commands for remote
operation.

•

Rate — Provides details on reading rate selection. Includes the SCPI commands
for remote operation.

•

Damping — Provides details on damping, including the SCPI commands for
remote operation.

•

Filters — Explains how to configure and control the digital and median filters.
Includes the SCPI commands for remote operation.

4-2

Range, Units, Digits, Rate, and Filters

Model 6487 Reference Manual

Range, units, and digits
Range
The ranges for current measurements are listed in Table 4-1.
Table 4-1
Measurement ranges
nA

μA

2nA
20nA
200nA

2μA
20μA
200μA

2mA
20mA

The full scale readings for every measurement range are 5% over range. For example, on
the 20µA range, the maximum input current is ± 21µA. Input values that exceed the maximum readings cause the overflow message (OVRFLOW) to be displayed.

Manual ranging
To select a range, press the RANGE or key. The instrument changes one range per
key-press. If the instrument displays the OVRFLOW message on a particular range, select
a higher range until an on-range reading is displayed. Use the lowest range possible without causing an overflow to ensure best accuracy and resolution.

Autoranging
When using autorange, the instrument automatically goes to the most sensitive available
range to measure the applied signal. Up-ranging occurs at 105% of range, while
down-ranging occurs at the range value. For example, if on the 20µA range, the instrument
will go up to the 200µA range when the input signal exceeds 21µA. While on the 200µA
range, the instrument will go down to the 20µA range when the input level goes below
20µA.
The AUTO key toggles the instrument between manual ranging and autoranging. The
AUTO annunciator turns on when autoranging is selected. To disable autoranging, press
AUTO or the RANGE or . Pressing AUTO to disable autoranging leaves the instrument on the present range.
Every time an autorange occurs, a search for every available range of the selected function
is performed. The time it takes to perform the search could slow down range change speed
significantly. Setting upper and/or lower autorange limits can reduce search time.
klqb

Range limits and groups are not in effect for manual ranging. Every range is
accessible with manual range selection.

Model 6487 Reference Manual

Range, Units, Digits, Rate, and Filters

4-3

Autorange limits
Search time for amps can be reduced by setting upper and/or lower autorange limits. For
example, if you know the maximum input will be around 1µA, set the upper current range
limit to 2µA. This eliminates the 20µA, 200µA, 2mA, and 20mA ranges from the search,
thereby increasing the range change speed. Should the input exceed 2.1µA, the
OVRFLOW message will be displayed.
Perform the following steps to set upper and/or lower autorange limits.
1.
2.

3.
4.

Press CONFIG key (CONFIGURE: will be displayed).
Display the desired limit (UPPER or LOWER):
a. Press the RANGE key to display the present UPPER range limit.
b. Press the RANGE key to display the present LOWER range limit.
Scroll through the available range limits using the or RANGE key.
Press ENTER when the desired range is flashing.

klqb

If you attempt to select an incompatible range limit, it will be ignored and TOO
LARGE or TOO SMALL will be displayed briefly. For example, if the lower
range limit is 20µA, trying to set the upper limit to 2µA will result in the TOO
SMALL error.

klqb

Changing the display resolution is not allowed if displaying readings in scientific notation.

Units

Readings can be displayed using engineering (ENG) units (i.e. 1.236 mA) or scientific
(SCI) notation (i.e. 1.236E-03A). Perform the following steps to change the units setting:
1.
2.
3.
4.
5.
6.

Press MENU key.
Scroll down to the UNITS item using the or RANGE key (UNITS: will be
flashing).
Press ENTER to select setting (ENG or SCI will be flashing).
Use the or key to display the desired units setting.
Press ENTER.
Press EXIT to return to normal display.

klqbp 1. The units setting can only be changed from the front panel (no remote
operation).
2. Scientific notation provides more resolution on small values than
engineering units.

4-4

Range, Units, Digits, Rate, and Filters

Model 6487 Reference Manual

Digits
The DIGITS key sets display resolution for the Model 6487. Display resolution can be set
from 3 to 6 digits. This single global setting affects display resolution for all measurement ranges.
To set display resolution, press (and release) the DIGITS key until the desired number of
digits is displayed.
klqb

Changing the integration rate does not change display resolution. Also changing
display resolution does not change the rate setting.
The voltage source value will not be displayed with the 6 digit setting.

SCPI programming — range and digits
Table 4-2
SCPI commands — digits
Commands
[:CURRent]
:RANGe
[:UPPer]
: AUTO
:ULIMit
:LLIMit

For Digits:
DISPlay
:DIGits

Description
Measure current:
Range selection:
Specify expected reading; -0.021 to 0.021 (A).
See Table 4-3.
Enable or disable autorange.
Specify upper range limit for autorange:
-0.021 to 0.021 (A).
Specify lower range limit for autorange:
-0.021 to 0.021 (A).

DISPlay Subsystem:
Set display resolution: 4 to 7, where of:
4 = 3 digit resolution
5 = 4 digit resolution
6 = 5 digit resolution
7 = 6 digit resolution
Note: Rational numbers can be used. For
example, to set 5 resolution send a value
of 4.5 (the 6487 rounds it to 5).

Default

200μA
ON
20mA
2nA

Model 6487 Reference Manual

Range, Units, Digits, Rate, and Filters

4-5

Programming example — range and digits
The following command sequence selects the 20mA range and sets display resolution to 3:
*RST
CURR:RANG 0.02
DISP:DIG 3.5

' Restore RST defaults.
' Set to 20mA range.
' Set display resolution to 3 digits.

Table 4-3
Ranges and values
Range
20mA
2mA
200µA
20µA
2µA
200nA
20nA
2nA

value
2E-2 or 0.02
2E-3 or 0.002
2E-4 or 0.0002
2E-5 or 0.00002
2E-6 or 0.000002
2E-7 or 0.0000002
2E-8 or 0.00000002
2E-9 or 0.000000002

Display (5 digit
resolution)
00.0000mA
0.00000mA
000.000µA
00.0000µA
0.00000µA
000.000nA
00.0000nA
0.00000nA

4-6

Range, Units, Digits, Rate, and Filters

Model 6487 Reference Manual

Rate
The RATE key selects the integration time of the A/D converter. This is the period of time
the input signal is measured. The integration time affects the amount of reading noise, as
well as the ultimate reading rate of the instrument. The integration time is specified in
parameters based on a number of power line cycles (NPLCs), where 1 PLC for 60Hz is
16.67msec (1/60) and 1 PLC for 50Hz (and 400Hz) is 20msec (1/50).
In general, the Model 6487 has a parabola-like shape for its speed vs. noise characteristics
and is shown in Figure 4-1. The Model 6487 is optimized for the 1 PLC to 10 PLC reading
rate. At these speeds (lowest noise region in the graph), The Model 6487 will make corrections for its own internal drift and still be fast enough to settle a step response <100ms.
Figure 4-1
Speed vs. noise characteristics

Lowest
noise
region

Voltage
Noise

166.7μs

16.67ms

166.67ms

Integration Time

The rate setting is global for all ranges. Therefore, it does not matter what range is presently selected when you set rate.
There are two ways to set rate. You can select slow, medium, or fast by using the RATE
key or you can set the number of power cycles from the NPLC menu that is accessed by
pressing CONFIG / LOCAL (while in LOCAL) and then RATE.
RATE Key — The RATE key selections are explained as follows:
•
•
•

SLOW — Selects the slowest preset integration time (6 PLC for 60Hz or 5 PLC for
50Hz). The SLOW rate provides better noise performance at the expense of speed.
MED — Selects the medium integration time (1 PLC). Select the MED rate when
a compromise between noise performance and speed is acceptable.
FAST — Selects the fastest preset integration time (0.1 PLC). Select the FAST rate if
speed is of primary importance (at the expense of increased reading noise).

Model 6487 Reference Manual

Range, Units, Digits, Rate, and Filters

4-7

To change the rate setting, press (and release) the RATE key until the desired rate annunciator (SLOW, MED, or FAST) is displayed.
NPLC Menu — From this menu you can set rate by setting the PLC value. Perform the
following steps to set NPLC:
1.
2.

3.
klqb

Press CONFIG / LOCAL and then RATE to display the present PLC value.
Use the , , , and keys to adjust to the desired PLC value. Valid values are:
60Hz operation: 0.01 to 60
50Hz operation: 0.01 to 50
Press ENTER.
The SLOW, MED, or FAST annunciator will only turn on if the set PLC value
corresponds exactly to the slow (5 or 6 PLC for the respective frequency of 50 or
60Hz), medium (1 PLC), or fast (0.1 PLC) integration rate. For example, with
the integration rate set to 2 PLC, none of the rate annunciators will turn on.

SCPI programming — rate
Table 4-4 contains the path and the command to set rate.
Table 4-4
SCPI commands — rate
Command

Description

Default

[:SENSe]
[:CURRent]
:NPLCycles

SENSe Subsystem:
Specify integration rate: 0.01 (PLCs) to
60.0 (60Hz) or 50.0 (50Hz)

6.0 (60Hz)
5.0 (50Hz)

Programming example — rate
The following command sets the integration rate for all measurement ranges to 2 PLC:
CURR:NPLC 2

' Set integration rate to 2 PLC.

4-8

Range, Units, Digits, Rate, and Filters

Model 6487 Reference Manual

Damping
High capacitance seen at the input will increase reading noise. This capacitance can be
attributed to a long input cable or to the capacitance of the source or a combination of
both. Enabling damping (analog filtering) will reduce this type of noise for current measurements. However, damping will also slow down the response of the measurement.
klqb

Use damping to reduce noise caused by input capacitance. Use filtering to
reduce noise caused by a noisy input signal.

To toggle damping on or off simply press the DAMP key. DAMP ON or DAMP OFF will
be displayed briefly to indicate the present state of damping. Note that the FILT
annunciator is used for both the analog damping filter and the two types of digital filters.
Table 4-5
SCPI commands — Damping
Command
[:SENSe]
[:CURRent]
:DAMPing
[:STATe]
[:STATe]?

Description
SENSe Subsystem:
Path to Current functions
Control Damping (analog filter)
Enable or disable damping filter.
Query damping filter state.

Default

Filters
Filtering stabilizes noisy measurements caused by noisy input signals. The Model 6487
uses two types of filters: median and digital. The displayed, stored, or transmitted reading
is simply the result of the filtering processes. Note that both the median and digital filters
can be in effect at the same time.
With both filters enabled, the median filter operation is performed first. After the median
filter yields a reading, it is sent to the stack of the digital filter. Therefore, a filtered reading
will not be displayed until both filter operations are completed.
The settings for the filter are global. The FILT key is used to control both filters. When
either the median or digital filter is enabled, the FILT annunciator is on. Note that the FILT
annunciator is used for both the digital filters and the analog damping filter.

Model 6487 Reference Manual

Range, Units, Digits, Rate, and Filters

4-9

Median filter
The median filter is used to determine the "middle-most" reading from a group of readings
that are arranged according to size. For example, assume the following readings:
20mA, 1mA, 3mA
The readings are rearranged in an ascending order as follows:
1mA, 3mA, 20mA
From the above readings, it is apparent that 3mA is the median (middle-most) reading.
The number of sample readings used for the median calculation is determined by the
selected rank (1 to 5) as follows:
Sample readings = (2 × R) + 1
where; R is the selected rank (1 to 5)
For example, a rank of 5 will use the last 11 readings to determine the median;
(2 × 5) + 1 = 11. Each new reading replaces the oldest reading and the median is then
determined from the updated sample of readings.
Median filter operation — The median filter operates as a moving type filter. For example, if the median filter is configured to sample 11 readings (Rank 5), the first filtered reading will be calculated (and displayed) after 11 readings are acquired and placed in its filter
stack. Each subsequent reading will then be added to the stack (oldest reading discarded)
and another median filter reading will be calculated and displayed. The median filter operation will reset (start over) whenever the Zero Check operation is performed or the range
is changed.

Median filter control
To configure the median filter:
1.
2.
3.
4.
5.
6.
7.

Press the CONFIG key.
Press the FILT key.
Select MEDIAN, then press ENTER.
Change the display to MEDIAN ON, then press ENTER.
The present rank will be displayed (flashing).
Use the RANGE ( or ) keys to display the desired rank (1 to 5).
Press ENTER to set. To return to the previously set value, press EXIT instead of
ENTER.

4-10

Range, Units, Digits, Rate, and Filters

Model 6487 Reference Manual

Digital filter
Digital filter types
An additional filter parameter is type (type is either moving or repeating). Filter types are
compared in Figure 4-2.
Moving Filter — Every time a reading conversion occurs, the readings in the stack are
averaged to yield a single filtered reading. The stack type is first-in, first-out. After the
stack fills, the newest reading conversion replaces the oldest. Note that the instrument does
not wait for the stack to fill before releasing readings.
Repeating Filter — Takes a selected number of reading conversions, averages them, and
yields a reading. It then flushes its stack and starts over.
Figure 4-2
Digital filter types; moving and repeating
A. Class - Average, Readings = 10, Type - Moving
Conversion #10
#9
#8
#7
#6
#5
#4
#3
#2
Conversion #1

Conversion #11

Reading
#10

#10
#9
#8
#7
#6
#5
#4
#3
Conversion #2

Conversion #12

Reading
#11

#11
#10
#9
#8
#7
#6
#5
#4
Conversion #3

Reading
#12

B. Class - Average, Readings = 10, Type - Repeating
Conversion #10
#9
#8
#7
#6
#5
#4
#3
#2
Conversion #1

Conversion #20

Reading
#1

#19
#18
#17
#16
#15
#14
#13
#12
Conversion #11

Conversion #30

Reading
#2

#29
#28
#27
#26
#25
#24
#23
#22
Conversion #21

Reading
#3

Model 6487 Reference Manual

Range, Units, Digits, Rate, and Filters

4-11

Response time
The various filter parameters have the following effects on the time needed to display,
store, or output a filtered reading:
•

Number of reading conversions — Speed and noise are tradeoffs.

Operation consideration
The digital filter operation will reset (start over) whenever the zero check operation is performed or the range is changed.

Digital filter control
To configure the average filter:
1.
2.
3.

Press CONFIG then FILT.
Set the display to AVERAGE ON, then press ENTER. The present number of reading conversions to average (filter count) will be displayed (flashing).
Set filter count (2 to 100):
• Use the RANGE and or keys to display the desired filter count value at the
RDGS prompt.
• Press ENTER to set.
Set filter type (REPEAT or MOVING AV):
• Use the RANGE keys to display the desired filter type at the TYPE: prompt.
• Press ENTER to set.

4-12

Range, Units, Digits, Rate, and Filters

Model 6487 Reference Manual

SCPI programming — filters
Table 4-6
SCPI commands — filters
Commands

Description

Default

For median filter:
[:SENSe[1]]
:MEDian
:RANK
[:STATe]

SENSe Subsystem:
Median Filter:
Specify filter rank: 1 to 5.
Enable or disable median filter.

1
OFF

For digital filter:
[:SENSe[1]]
:AVERage
:TCONtrol
:COUNt
[:STATe]

SENSe Subsystem:
Digital Filter:
Select filter control: MOVing or REPeat.
Specify filter count: 2 to 100.
Enable or disable digital filter.

MOV
10
OFF

Programming example
The following command sequence configures and enables both filters:
' Median Filter:
MED:RANK 5
MED ON

' Set rank to 5.
' Enable median filter.

' Digital Filter:
AVER:COUN 20
AVER:TCON MOV
AVER ON

' Set filter count to 20.
' Select moving filter.
' Enable digital filter.

Relative, mX+b, m/X+b, and log
•

Relative — Explains how to null an offset or establish a baseline value. Includes
the SCPI commands for remote operation.

•

mX+b, m/X+b (reciprocal), and logarithmic — Covers these three basic math
operations and includes the SCPI commands for remote operation.

5-2

Relative, mX+b, m/X+b, and log

Model 6487 Reference Manual

Relative
Relative (Rel) nulls an offset or subtracts a baseline reading from present and future readings. When a Rel value is established, subsequent readings will be the difference between
the actual input and the Rel value.
Displayed (Rel’ed) Reading = Actual Input - Rel Value
A Rel value is the same for all measurement ranges. For example, a Rel value of 1E-6 is
1µA on the 2µA range. It is also 1µA on the 20µA range and the 200µA range. Note
changing ranges does not disable Rel.
When a Rel value is larger than the selected range, the display is formatted to accommodate the Rel’ed reading. However, this does not increase the maximum allowable input for
that range. An over-range input signal will still cause the display to overflow. For example,
on the 20µA range, the Model 6487 still overflows for a 21µA input.
klqb

Rel can be used on the result of the mX+b, m/X+b, or LOG calculations. However, Rel will disable whenever a math function is enabled or disabled.

Setting and controlling relative
From the front panel, there are two ways to set the Rel value. You can use the input reading
as the Rel value or you can manually key in the Rel value.

REL key
When the REL key is used to enable Rel, the present display reading is used as the Rel
value. Perform the following steps to set a Rel value:
1.
2.

3.
4.
klqb

Disable zero check by pressing ZCHK.
Display the reading you want as the Rel value. This could be a zero offset reading
that you want to null out or it could be an applied level that you want to use as a
baseline.
Press REL. The REL annunciator turns on and subsequent readings will be the difference between the actual input and the Rel value.
To disable REL, press the REL key a second time or select a different measurement
function. The REL annunciator turns off.
When Rel is disabled, the Rel value is remembered. To reinstate the previous Rel
value, press CONFIG then press REL and finally press ENTER. If the REL is
disabled and then REL is pressed again, it will determine and set a new null
value.
With zero check enabled, the REL key controls zero correct, not relative.

Model 6487 Reference Manual

Relative, mX+b, m/X+b, and log

5-3

Displaying or manually keying in REL
Pressing CONFIG and then REL displays the present Rel value. This displayed Rel value
can be enabled (pressing ENTER) or a different Rel value can be entered and enabled.
1.
2.

Press CONFIG and then REL. The present Rel value will be displayed.
To change the Rel value, use the RANGE and cursor keys and change the value. To
change Rel polarity, place the cursor on the polarity sign and press either manual
RANGE key. To change the Rel range, place the cursor on the range symbol (at the
end of the reading) and use the manual RANGE keys (Table 5-1).
With the desired Rel value displayed, press ENTER to enable Rel.
Table 5-1
Range symbols for rel values
Symbol

Prefix

Exponent

pico-

10-12

nano-

10-9

micro-

10-6

milli-

10-3

(none)

100

kilo-

103

mega-

106

giga-

109

tera-

1012

5-4

Relative, mX+b, m/X+b, and log

Model 6487 Reference Manual

SCPI programming — relative
Table 5-2
SCPI commands — relative (null)
Commands
CALCulate2

Description

Default

Ref

SENS1

Path to configure and control limit testing (CALC2):

:FEED

Specify reading to Rel: SENSe[1] or CALCulate[1].

:NULL

Configure and control Relative.

:ACQuire

Use input signal as Rel value.

:OFFSet

Specify Rel value: -9.999999e20 to 9.999999e20.

0.0

:STATe

Enable or disable Rel.

OFF

:DATA?

Return Rel’ed readings triggered by INITiate.

:DATA:LATest?
INITiate

Return only the latest Rel’ed reading.

B
C
C

Trigger one or more readings.

A) :FEED
With SENSe[1] selected, the Rel operation will be performed on the input signal. With
CALCulate[1] selected, the Rel operation will be performed on the result of the mX+b or
m/X+b calculation.

B) :STATe
This command toggles the state of Rel without acquiring new values. This operation is different than the REL key on the front panel (which toggles the Rel state) — the front panel
key acquires new values when pressed (unless CONFIG is pressed first). If a NULL value
has not been acquired before enabling Rel, 0.000000E+00 will be used.

C) :DATA? and :DATA:LATest?
With Rel enabled, these commands will return one or more Rel’ed readings. They will not
trigger fresh (new) readings. Use the INITiate command to trigger new readings (see
Section 7 for details on INITiate).
If the instrument is programmed to perform a finite number of measurements, the :DATA?
command will return all the Rel’ed readings after the last reading is taken. The
:DATA:LATest? command will only return the last (latest) Rel’ed reading.

Model 6487 Reference Manual

Relative, mX+b, m/X+b, and log

5-5

If the instrument is programmed to perform an infinite number of measurements (arm
count or trigger count set to infinite), you cannot use the :DATA? command to return
Rel’ed readings. However, you can use the :DATA:LATest? command to return the last
Rel’ed reading after aborting the measurement process. After sending the INITiate command to start the measurement process, use the ABORt command to abort the measurement process, then use :DATA:LATest? to return to the last Rel’ed reading.

Programming example — relative
This program fragment establishes a 1µA baseline for measurements:
CALC2:NULL:OFFS 1e-6
CALC2:NULL:STAT ON
CALC2:FEED SENS
SYST:ZCH OFF
INIT
CALC2:DATA?

'
'
'
'
'
'

Set Rel value of 1μA.
Enable Rel.
Rel input signal.
Turn off zero check.
Trigger reading(s).
Request Rel’ed reading.

mX+b, m/X+b (reciprocal), and logarithmic
mX+b and m/X+b
The following math operations manipulate normal display readings (X) mathematically
according to the following calculations:
Y = mX+b
Y = m/X+b
where: X is the normal display reading
m and b are user-entered constants for scale factor and offset
Y is the displayed result
klqb

Changing the “m” or “b” for mX+b also changes it for m/X+b.

Configuring and controlling mX+b and m/X+b
To configure and control either of these math calculations, perform the following steps:
klqb
1.
2.

Enabling or disabling math disables Rel (if Rel is enabled).
Press CONFIG then MATH to enter the math configuration menu.
Using the manual RANGE keys, select either MATH: mX+B or MATH: M/X+B,
then press ENTER to select the desired function and display the present scale
factor:
M: +1.000000 ^ (factory default)

5-6

Relative, mX+b, m/X+b, and log

Model 6487 Reference Manual

Key in a scale factor value. The and keys control cursor position and the and
RANGE keys increment and decrement the digit value. To change range, place
the cursor on the range symbol and use the and keys. With the cursor on the
polarity sign, the and keys toggle polarity.

klqb
4.

Range symbols are defined in Table 5-1.
Press ENTER to enter the M value and display the offset (B) value:
B: +0.000000 P (factory default)
Key in the offset value.
Press ENTER to set the B value and display the one-character UNITS designator:
UNITS: X (factory default)

5.
6.
klqb

The configuration for mX+b calculations consists of a units designator, a value
for M, and a value for B. This configuration is used for both the mX+b and the
m/X +b calculations. Therefore, changing either configuration (of the mX+b or
the m/X+b calculation) also changes the other calculation’s configuration.
To change the units designator (default is “X”), press the cursor key and use
the manual RANGE keys. The character can be any letter in the alphabet
(A through Z).
Press ENTER.
To enable math, press the MATH key from normal display. The MATH annunciator
and the units designator will turn on and the result of the calculation will be
displayed.

8.
9.

Logarithmic
This calculation converts input readings to logarithm base 10 values. The calculation is
performed as follows:
log

X = Y

where: X is the input reading
y is the logarithmic result
For example: Assume that exactly 1mA is being measured by the Model 6487.
log 101.000000mA = – 3

klqb

This calculation uses the absolute value of the normal input reading, as the log
of a negative number cannot be computed.

Model 6487 Reference Manual

Relative, mX+b, m/X+b, and log

5-7

To control log, perform the following steps:
klqb
1.
2.
3.

Enabling or disabling math disables Rel (if Rel is enabled).
Press CONFIG then MATH to enter the math configuration menu.
Using either manual RANGE key, select MATH: LOG10, then press ENTER to
select the log function.
To enable math, press the MATH key from normal display. The MATH annunciator
and the “L” designator will turn on and the result of the calculation will be
displayed.

SCPI programming — mX+b, m/X+b, and log
Table 5-3
SCPI commands — mX+b, m/X+b, and log
Commands
CALCulate[1]
:FORMat
:KMATh
:MMFactor
:MBFactor
:MUNits
:STATe
:DATA?
:DATA:LATest?

Description
CALCulate1 Subsystem:
Select calculation: MXB, RECiprocal, or LOG10.
Path to configure mX+b and m/X+b:
Specify scale factor (M) for mX+b and m/X+b:
-9.99999e20 to 9.99999e20.
Specify offset (B) for mX+b and m/X+b:
-9.99999e20 to 9.99999e20.
Specify units for mX+b or m/x+b result:
1 character: A–Z, ‘[‘=¾, ‘\’=°, ‘]’=%.
Enable or disable the selected calculation.
Returns all CALC1 results triggered by the INITiate.
Returns only the latest CALC1 reading.

Default

Ref

MXB

A
B

1.0
0.0
“X”
OFF
C
C

A) :FORMat
This command selects the desired math function in the same manner as the front panel
CONFIG MATH menu. Functions names include MXB (mX + b), RECiprocal (m/X + b),
and LOG10.

B) :KMATh
Use these commands to set the M (scale factor), B (offset), and units for the MX + B and
reciprocal math functions.

5-8

Relative, mX+b, m/X+b, and log

Model 6487 Reference Manual

C) :DATA? and :DATA:LATest?
The INITiate command must be sent to trigger the measurements and calculations. The
number of calculations depend on how many measurements the instrument is programmed
to perform.
If the instrument is programmed to perform a finite number of measurements, the :DATA?
command will return all the CALC1 readings after the last reading is taken. The
:DATA:LATest? command will only return the last (latest) CALC1 reading.
If the instrument is programmed to perform an infinite number of measurements (arm
count or trigger count set to infinite), you cannot use the :DATA? command to return
CALC1 readings. However, you can use the :DATA:LATest? command to return the last
CALC1 reading after aborting the measurement process. After sending the INITiate command to start the measurement process, use the ABORt command to abort the measurement process, then use :DATA:LATest? to return the last CALC1 reading.

Programming example — mX+b
This command sequence performs a single mX+b calculation, using “X” as the units designator, and displays the result on the computer CRT:
*RST
CALC:FORM MXB
CALC:KMAT:MMF 2e-3
CALC:KMAT:MBF 5e-4
CALC:KMAT:MUN ‘X’
CALC:STAT ON
SYST:ZCH OFF
INIT
CALC:DATA?

'Restore RST defaults.
'Select mX+b calculation.
'Set scale factor (M) to 2e-3.
'Set offset (B) to 5e-4.
'Select X as units.
'Enable calculation.
'Disable zero check.
'Perform one measurement and
'calculate mX+b.
'Request mX+b result.

Buffer and Sweeps
•

Buffer operations — Explains how to store and recall readings including buffer
statistics.

•

Voltage sweeps — Discusses how to generate sweeps using the voltage source.

6-2

Buffer and Sweeps

Model 6487 Reference Manual

Buffer operations
The Model 6487 has a buffer to store from one to 3000 readings. It also stores overflow
readings and the voltage source value. Each reading has a timestamp. The timestamp for
each reading is referenced to the time the measure/store process is started. In addition,
recalled data includes statistical information (maximum, minimum, peak-to-peak,
average, and standard deviation).
The buffer fills with the specified number of readings and stops. Readings are placed in the
buffer after any filters and/or math operations have been performed. Math operations
include relative, mX+b, m/X+b, LOG, or limit tests.
Buffered data is overwritten each time the storage operation is selected. The data is
volatile — it is not saved through a power cycle.
Measurement function changes are permissible during the storage process. Note however,
that the statistics will be based on the readings of the different measurement functions.

Store
Perform the following steps to store readings:
1.
2.
3.
4.
5.

klqb

Set up the instrument for the desired configuration.
Press CONFIG (CONFIGURE: will be displayed).
Press STORE. The present buffer size (in readings) is displayed.
Use the cursor and keys and the RANGE and keys to set the number of
readings to store (1 to 3000).
Press ENTER to save the buffer size. Press the STORE key. If in the immediate
trigger mode, the storage process will start immediately. If in the external input
trigger mode, each input trigger (or press of TRIG key) will store a reading. See
Section 7 for information on triggering.
The asterisk (*) annunciator turns on to indicate that the data storage operation
is enabled. It will turn off when the storage process is finished (buffer full).

Recall
Perform the following steps to view stored readings and buffer statistics:
1.
2.

Press RECALL. The message RDG NO. 1 is displayed. Note that the arrow annunciator (↔) also turns on to indicate that additional data is available for viewing.
Use the RANGE and keys and the cursor and keys to navigate through the
reading numbers and buffer statistics, reading values, voltage source values, and
timestamps (Figure 6-1). For information on how to set buffer timestamps, see
“Buffer timestamps,” page 6-3.
Press EXIT to return to the normal display.

Model 6487 Reference Manual

Buffer and Sweeps

6-3

XX
XX

Buffer Statistics

▲

Reading Value
Reading Value
Reading Value
Reading Value
Reading Value
Reading Value
Reading Value
Reading Value
Reading Value
Readingg Value
Standard Deviation Value
Average Value
Peak to Peak Value
Minimum Value
Maximum Value

Vsource
Vsource
Vsource
Vsource
Vsource
Vsource
Vsource
Vsource
Vsource
Vsource
---------------------------Vsource
Vsource

Voltage Source

▲

RANGE

10
9
8
7
6
5
4
3
2
1

▲

RANGE

RDG
NO.
RDG
NO.
RDG
NO.
RDG
NO.
RDG
NO.
RDG
NO.
RDG
NO.
RDG
NO.
RDG
NO.
RDG
NO.
STD
DEV
AVERAGE
PK-PK
MIN
AT
MAX
AT

▲

Figure 6-1
Buffer locations

Timestamp
Timestamp
Timestamp
Timestamp
Timestamp
Timestamp
Timestamp
Timestamp
Timestamp
Timestamp
Timestamp
---------------------------Timestamp
Timestamp

Buffer Timestamps

Buffer timestamps
Use the TSTAMP: menu item to change the timestamp format. To access the menu:
1.
2.
3.
4.
5.
6.

Press MENU.
Scroll to the TSTAMP: menu item using RANGE and keys.
Press ENTER.
Using RANGE and keys, select desired setting. Available options are ABS
(absolute) or DELT (delta).
ABS: each timestamp is referenced to the first reading stored in the buffer. The first
reading always has a timestamp of 0000000.0000.
DELT: each timestamp provides the time between the readings.

6-4

Buffer and Sweeps

Model 6487 Reference Manual

Buffer statistics
•
•

•

MIN and MAX provides the minimum and maximum readings stored in the buffer.
It also indicates the buffer location of these readings.
The PK-PK (peak-to-peak) value is the difference between the maximum and
minimum readings stored in the buffer:
PK-PK = MAX - MIN
Average is the mean of the buffer readings. Mean is calculated as follows:
n

Xi
Σ -----

y =

n
i=1

Where: Xi is a stored reading
n is the number of stored readings
•

The STD DEV value is the standard deviation of the buffered readings. Standard
deviation is calculated as follows:

Σ ( Avg – Xi )

y =

i =1
----------------------------------n–1

Where: Xi is a stored reading
n is the number of stored readings
Avg is the mean of the buffer readings
klqb

If any readings stored in the buffer are the result of an overflow or overvoltage
condition, the buffer statistics calculation will not be performed. Buffer recall
via front panel operation will show a series of dashes in place of the requested
buffer statistics value. In remote operation, the corresponding buffer statistics
will be represented by the value +9.91e37.

SCPI programming
Commands associated with buffer operation are listed in Table 6-1. The TRACe commands are used to store and recall readings in the buffer. The FORMat:ELEMents command is used to specify which data elements to include in the response message for
TRACe:DATA? (which is the command to read the buffer). The CALCulate3 commands
are used to obtain statistics from the buffer data.

Model 6487 Reference Manual

klqb

Buffer and Sweeps

6-5

The Model 6487 uses IEEE-754 floating point format for statistics calculations.
When programming the buffer via remote, the trigger count set with the
TRIG:COUN command should normally equal the number of buffer readings to
store set with TRAC:POIN. See Section 7 for details on triggering.
If the voltage source was in compliance when the reading was acquired, the
recalled front panel SRC: display will show the voltage value dimmed. Over the
GPIB, a value of -999 returned for the voltage source element indicates that the
source was in compliance.
For any ohms measurements, the ohms reading is invalid and unknown if the
voltage source is in compliance. Therefore, a value of -9.9e+36 will be returned
over the GPIB and the message I-LIMIT will be displayed on the front panel for
both normal readings and buffer recall readings for any ohms readings where
the voltage source went into compliance.

Table 6-1
SCPI commands — buffer
Commands
:TRACe
:CLEar
:FREE?
:POINts
:ACTual?
:FEED
:CONTrol
:TSTamp
:FORMat
:DATA?
:MODE?

Description

Default

TRACe Subsystem:
Clear readings from buffer.
Query bytes available and bytes in use.
Specify number of readings to store: 1 to 3000.
Returns number of readings actually stored in buffer.
Select source of readings: SENSe[1], CALCulate[1], or
CALCulate2.
Select buffer control mode: NEVer or NEXT.
Timestamp:
Select timestamp format: ABSolute or DELTa.
Read all readings in buffer.
Query the type of data (DC or AVOL) stored in the
buffer.

See Note

:FORMat
:ELEMents

FORMat Subsystem:
Specify data elements for :TRACe:DATA? response
message: READing, UNITs, VSOurce, TIME,
STATus, ALL, or DEFault (all elements except
VSOurce).

:CALCulate3
:FORMat

CALCulate3 Subsystem:
Select buffer statistic: MINimum, MAXimum, MEAN,
SDEViation, or PKPK.
Read the selected buffer statistic.

:DATA?

Ref

A
100
SENS1

NEV

ABS

D
E

All
except
VSO

MEAN

Note: SYSTem:PRESet and *RST have no effect on :TRACe commands. The listed defaults are power-on defaults.

Section 13
F

G
H

6-6

Buffer and Sweeps

Model 6487 Reference Manual

A) :TRACe:FREE?
Two values, separated by commas, are returned. The first value indicates how many bytes
of memory are available and the second value indicates how many bytes are reserved to
store readings.

B) :TRACe:FEED
Name parameters:
•
•
•

SENSe — Raw input readings are stored in the buffer.
CALCulate1 — The results of the mX+b, m/X+b, or log calculation are stored in
the buffer. See Section 5 for information on mX+b, m/X+b, or log.
CALCulate2 — Test limit or Rel readings are stored in the buffer. See Section 8 for
information on limit tests.

C) :TRACe:FEED:CONTrol
Name parameters:
•
•

NEXT — Enables the buffer and turns on the asterisk (*) annunciator. After the
buffer stores the specified number of readings, the asterisk annunciator turns off.
NEVer — Disables the buffer.

D) :TRACe:TSTamp:FORMat
Name parameters:
•
•
•

ABSolute — Each timestamp is referenced to the first reading stored in the buffer.
DELTa — Timestamps provide the time between each buffer reading.
The timestamp data element can be included with each buffer reading (see Ref F).

:TRACe:DATA?
1.
2.
3.

The response message will include one to four data elements for each stored reading. Use the FORMat:ELEMents command (see Ref F) to specify the elements.
Reading an empty buffer will result in the “ERROR: -230” display message.
Buffer data can be sent in the binary format. (See “FORMat subsystem,” page 13-4
for details).

Model 6487 Reference Manual

Buffer and Sweeps

6-7

:FORMat:ELEMents

List parameters:
•
•
•
•
•
•
•
•

READing — Includes the buffer reading in each data string.
UNITs — Identifies amps, ohms, or math units.
VSOurce — Includes voltage source value in each reading string.
TIME — Includes the timestamp for each reading. Timestamp can be in the absolute or delta format (see Ref D).
STATus — Includes a status word for each reading. It provides status information
on instrument operation. (See “FORMat subsystem,” page 13-4.)
DEFault — All except VSource.
ALL — Includes all reading elements.
At least one data element must be in the list. Listed elements must be separated by
a comma (i.e. FORMat:ELEMents, READing, TIME). Elements not listed will not
accompany the response message for TRACe:DATA?. Data in the response message will be in order of the listed data elements set by this command.

G) :CALCulate3:FORMat
This command selects the statistic to be returned by CALCulate3:DATA? (see Ref H).
Name parameters:
•
•
•
•
•

MINimum — Select the lowest reading stored in the buffer.
MAXimum — Select the largest reading stored in the buffer.
MEAN — Select the mean average statistic for the readings stored in the buffer.
SDEViation — Select the standard deviation statistic for the readings stored in the
buffer.
PKPK — Select the peak-to-peak statistic for readings stored in the buffer.
Peak-to-Peak is calculated as follows: PKPK = MAXimum - MINimum.

H) :CALCulate3:DATA?
1.
2.

If the number of data points in the buffer is one or none, CALCulate3:DATA? will
result in an error (-230).
If there is a lot of data in the buffer, some statistic operations may take too long and
cause a bus time-out error. To avoid this, send CALC3:DATA? and then wait for
the MAV (message available) bit in the Status Byte Register to set before addressing the Model 6487 talk (Section 10).

6-8

Buffer and Sweeps

Model 6487 Reference Manual

Programming example
The following program fragment stores 20 readings into the buffer and then calculates the
mean average on the buffer readings:
' Select data elements:
*RST
FORM:ELEM READ,TIME
' Store and Recall Readings:
TRIG:COUN 20
TRAC:POIN 20
TRAC:FEED SENS
TRAC:FEED:CONT NEXT
SYST:ZCH OFF
INIT
TRAC:DATA?

' Return 6487 to RST defaults.
' Select reading and timestamp.

'
'
'
'
'
'
'
'

Set trigger model to take 20 readings.
Set buffer size to 20.
Store raw input readings.
Start storing readings.
Disable zero check.
Trigger readings setup to SRQ on
buffer full.
Request all stored readings.

' Acquire Mean Statistic for Buffer Readings:
CALC3:FORM MEAN
' Select mean statistic.
CALC3:DATA?
' Request mean statistic.

Voltage sweeps
The Model 6487 voltage source can be used to generate voltage sweeps from a start voltage to a stop voltage at discrete step voltages. The Model 6487 stores readings in the
buffer for later recall, one set of readings per voltage step.

Overview
As shown in Figure 6-2, a voltage sweep is performed from a start voltage to a step voltage
at discrete step voltages. At each step voltage:
•
•
•

The source voltage is set to the new value.
The unit waits for the programmed delay period.
The reading is taken and stored in the buffer for later recall.

Note that sweeps can be positive-going or negative-going by programming the start and
stop voltages accordingly, but the programmed step voltage is always positive.

Model 6487 Reference Manual

Buffer and Sweeps

6-9

The front panel sweep parameters are not error checked until you have entered a STEP
value. If there are too many points, the error message “TOO MANY PTS” briefly appears
and you will be taken back to the start (STRT) value entry menu.
Likewise, a step size larger than the (stop-start) interval results in the message “STEP
TOO BIG”. Note that as long as the front panel V-MODE setting is SWEEP, the TRIG key
will function to initiate sweeps rather than as a trigger source. To return the TRIG key to
its normal behavior, use CONFIG -> OPER to set V-MODE back to DC.
Figure 6-2
Voltage sweeps
Delay
X

Step

Delay
X

Step
Delay
X

Step
Start

Delay
X

Note: X = Measurements taken.

Stop

6-10

Buffer and Sweeps

Model 6487 Reference Manual

Sweep operation
Using Table 6-2 as a guide, follow these steps to generate sweeps from the front panel:
1.
2.
3.
4.
5.
6.
7.

Press CONFIG then OPER. The unit will prompt for DC or SWEEP operation.
Select SWEEP, then press ENTER. The unit will prompt for the STRT (start)
voltage.
Using the manual RANGE and cursor keys, enter the desired start voltage, then
press ENTER. The unit will then prompt for the STOP voltage.
Enter the stop voltage, then press ENTER. The unit will prompt for the step
voltage.
Enter the step voltage, then press ENTER. The unit will prompt for the delay.
Enter the delay period, then press ENTER. The unit will prompt you to press TRIG
to start the sweep. The SCAN annunciator will be on to show the sweep is armed.
To start a sweep, press the TRIG key. The voltage source will be placed in operate,
the sweep will be performed, and readings will be stored in the buffer for later
recall. To abort a sweep in progress, press the EXIT key.

Table 6-2
Sweep parameter menu selections
Sweep Menu

Description

Default

STRT

Start voltage (-505 to 505V).

STOP

Stop voltage (-505 to 505V).

10V

STEP

Step voltage (-505 to 505V).

DEL

Delay between source and measure (0s to 999.9999s).

Recalling sweep data
To recall sweep data, press the RECALL key then use the manual RANGE and cursor
keys to display readings. See “Recall,” page 6-2 for more information.

Operating considerations
Buffer
The reading (TRACe) buffer is cleared at the start of the sweep and readings collected
during the sweep are placed into the buffer. The voltage source value is stored as a reading
element.

Model 6487 Reference Manual

Buffer and Sweeps

6-11

Source range
The source range will be fixed at the lowest range required to properly handle all points in
the sweep. For example, a 10-point sweep from +2V to +11 V in 1V steps will start on the
50V range and remain on the 50V range for all points in the sweep.

Sweep direction
Sweeps can go in either direction, but the STEP is an absolute value and is always positive. It can range from zero to the value of (START - STOP).

Command restrictions
While a sweep is in progress, most voltage source control commands, trigger model commands, and buffer (TRACe subsystem) commands are locked out. Sending any of the
commands listed below generates the error code +840 “Not allowed with sweep on”:
SOUR:VOLT[:LEV][:IMM][:AMPL]
SOUR:VOLT:STATe
SOUR:VOLT:RANGe
ARM:SEQ1:COUN
ARM:SEQ1:SOUR
ARM:SEQ1:TIM
TRIG:SEQ1:COUN
TRIG:SEQ1:SOUR
TRIG:SEQ1:DEL
TRIG:SEQ1:DEL:AUTO
TRAC:FEED
TRAC:FEED:CONT
TRAC:POIN
TRAC:CLE
TRAC:TST:FORM

Sweep example
For a linear sweep from -25V to +25V in 5 V steps, sweep parameters would be set as
follows:
•
•
•

Start: -25
Stop: 25
Step: 5

This sweep will have 11 points corresponding to the voltage source values -25, -20, -15,
-10, -5, 0, 5, 10, 15, 20, and 25. Changing the step to 7V results in values of -25, -18, -11,
-4, 3, 10, 17, and 24, which shows that only complete steps are executed.

6-12

Buffer and Sweeps

Model 6487 Reference Manual

SCPI programming — sweeps
Interlock
Attempting to initialize a sweep over the front panel while the interlock is open and failing
will result in the error message "CLOSE INTLCK" being displayed. If trying to arm
remotely with the SOUR:VOLT:SWE:INIT command, the error event +802 "Output
Blocked by Interlock"is generated.

Trigger model
Sweeps do not change any of the trigger model settings (Section 7), other than to internally perform the equivalent of an ABORt command and return to the Idle layer when the
SOUR:VOLT:SWE:INIT command is received. Trigger and Arm Counts, sources, and
delays are exactly what they were before the sweep was started. The only difference is that
the sweep delay is added between the setting of the source to the new value and the acquisition of the reading.The implications of this fact are that you must have the trigger and
arm counts properly set before sending the SOUR:VOLT:SWE:INIT command.
Example A
*RST
SYST:ZCH OFF
SOUR:VOLT:SWE:STAR 0
SOUR:VOLT:SWE:STOP 10
SOUR:VOLT:SWE:STEP 1
SOUR:VOLT:SWE:DEL 2
SOUR:VOLT:SWE:INIT
INIT:IMM
Because the *RST command sets the ARM and TRIG layer counts both to 1, the
INIT:IMM will take only a single reading in the sweep. To collect all 11 readings, you
would need to send eleven INIT:IMM commands. After each INIT:IMM command
arrives, the source will jump immediately to the new voltage, there will be a two-second
delay, then the reading will be collected.
Example B
*RST
SYST:ZCH OFF
ARM:COUN INF
SOUR:VOLT:SWE:STAR 0
SOUR:VOLT:SWE:STOP 10
SOUR:VOLT:SWE:STEP 1
SOUR:VOLT:SWE:DEL 2
SOUR:VOLT:SWE:INIT
INIT:IMM

Model 6487 Reference Manual

Buffer and Sweeps

6-13

This example is the same as before except that a setting for the ARM layer count to infinite
has been added. Now, after the INIT:IMM is received, the sweep will begin and all 11
points will be collected with no further commands required. Each point will be spaced
roughly two seconds apart (slightly longer due to the fact that the command sequence
leaves Autozero on). Once the sweep is complete, the source will go to 0V and will be
turned off, but readings will continue to be taken since the ARM count is infinite. These
readings will no longer be separated by the 2-second sweep delay, but instead will be collected at the normal (Slow, 6 PLC) rate.

Status model
Bit 3 of the Operation Condition Register (Section 10) is used to indicate that a sweep is in
progress. It will be set true when the SOUR:VOLT:SWE:INIT command is received and it
remains high until either the last sweep point is completed or a SOUR:VOLT:SWE:ABOR
command is received.
Table 6-3
SCPI commands — sweeps
Commands
SOURce[1]
:VOLTage
:SWEep
:STARt
:STOP
:STEP
:CENTer
:SPAN
:DELay
:INITiate
:ABORt
:STATe?
INITiate

Description
SOURce1 subsystem:
Voltage source commands:
Sweep commands
Set start voltage: -505V to 505V.
Program stop voltage: -505V to 505V.
Program step voltage: -505V to 505V.
Program center voltage: -505V to 505V.
Program span voltage: -505V to 505V.
Set delay: 0 to 999.9999s.
Arm sweep, put source in operate.
Abort sweep, put source in standby.
Query if sweep running: 1 = sweep in progress.
Trigger sweep.

Default

Ref.

0V
10V
1V
5V
10V
1s

A
B
C
D
E
F
G
H
I

A) :VOLTage:SWEep:STARt
This command programs the start voltage, which is the initial setting of the voltage source
during the sweep.

B) :VOLTage:SWEep:STOP
This command programs the stop voltage, which is the final setting of the voltage source
during the sweep.

6-14

Buffer and Sweeps

Model 6487 Reference Manual

C) :VOLTage:SWEep:STEP
This command programs the step voltage. In cases where there are not an exact number of
steps between the start and stop point, the last step will be truncated. Step sizes larger than
the (stop - start) interval will generate Error -842 “Sweep step size too large”. Step sizes
that will result in a sweep with more than the 3,000 point buffer maximum or below the
minimum source resolution for the source range required by the sweep will also generate
Error +841 “Sweep step size too small”. The STEP size is an absolute value, so the lower
limit is zero and the upper limit is restricted by the STARt and STOP settings.

D) :VOLTage:SWEep:CENTer
This command enters the mid-point of the sweep. Note that CENTer and SPAN are intimately coupled with STARt and STOP and simply offer another way to specify the sweep.

:VOLTage:SWEep:SPAN

This command enters the total span of the sweep. CENTer and SPAN are coupled with
STARt and STOP and are another way to specify the sweep.

:VOLTage:SWEep:DELay

This command programs the delay period, which is the time that the Model 6487 waits
after sourcing the voltage before starting to take the measurement at each step.

G) :VOLTage:SWEep:INITiate
This command places the voltage source in operate and begins sweep operation with the
next trigger. Once the sweep is triggered, the buffer is opened and the unit begins saving
readings. Error checking is held off until the SOUR:VOLT:SWEep:INIT command is sent.
A step size that is too small and would result in more than 3,000 points in the sweep generates Error +841 “Sweep step size too small”. If the step size exceeds the interval (STOP
- STARt), then you get Error +842 “Sweep step size too large”.

H) :VOLTage:SWEep:ABORt
This command immediately places the voltage source in standby (Operate off), cancels
buffer storage, and restores the trigger model to its prior settings before the sweep was
started.

:VOLTage:SWEep:STATe?

This query provides a means to determine whether or not a sweep is still running. A
returned value of 1 indicates that the sweep is still in progress, while a value of 0 shows
that no sweep is active.

Model 6487 Reference Manual

Buffer and Sweeps

6-15

Programming example
The following command sequence performs a sweep from 1V to 10V in 1V increments
and recalls all readings:
*RST
SOUR:VOLT:SWE:STAR 1
SOUR:VOLT:SWE:STOP 10
SOUR:VOLT:SWE:STEP 1
SOUR:VOLT:SWE:DEL 0.1
ARM:COUN INF
FORM:ELEM READ,VSO
SOUR:VOLT:SWE:INIT
SYST:ZCH OFF
INIT
TRAC:DATA?

'
'
'
'
'
'
'
'
'
'
'

Return 6487 to RST defaults.
Start voltage = 1V.
Stop voltage = 10V.
Step voltage = 1V.
0.1s delay.
Reset arm count.
Select reading, voltage source data.
Arm sweep, put source in operate.
Turn off zero check.
Trigger sweep.
Request all stored sweep readings.

Triggering
•

Trigger models — Explains the various components of the trigger models which
control the triggering operations of the instrument. Also, explains how to configure
the trigger model from the front panel.

•

SCPI programming — Includes the commands used to configure the trigger
model and the commands to control the measurement process.

•

External triggering — Explains external triggering which allows the Model 6487
to trigger other instruments and to be triggered by other instruments.

7-2

Triggering

Model 6487 Reference Manual

Trigger models
The flowcharts in Figure 7-1 and Figure 7-2 summarize triggering for the Model 6487.
They are called trigger models because they are modeled after the SCPI commands to control triggering (operation).
Figure 7-1
Trigger model — front panel operation
Turn 6487 ON
Press HALT

Halt
?

Yes

Idle

Bypass
Once
Arm Event
Detector
?

✛ Immediate

GPIB
Timer
Manual
TLink
/STest
STest
BSTest

Yes

✛ Never
Arm-In
Source

Arm Event
Detector

Another
Arm
?

Output
Trigger
(TL Done)

✛ Immediate Trigger-In
Source
TLINk

Trigger Event
Detector

✛ 0.0 sec Trigger Delay

✛ Factory Default

Output Trigger

MEASURE
Action

Arm
Layer

✛

On/Off

Trigger
Layer

Bypass
Once
Trigger Event
Detector
?

✛ Never

Arm
Count
✛ INF

No
Yes

Another
Trigger
?

Output Trigger
(VMC)

Trigger
Count
✛1

✛

On/Off

Model 6487 Reference Manual

Triggering

7-3

Figure 7-2
Trigger model — remote operation
See Note

INITiate
?

Idle

Yes

Arm
Layer
ARM
:DIRection
ARM:SOURce
ARM:SOURce
ARM:SOURce
ARM:SOURce
ARM:SOURce
ARM:SOURce
ARM:SOURce
ARM:SOURce

IMMediate
BUS
TIMer
MANual
TLINk
Arm-In
NSTest
Event
PSTest
BSTest

SOURce

No
Yes

ACCeptor

Another
Arm
?

ARM:COUNt

Arm Event
Detector
ARM:OUTPut

TRIGger|NONE

Trigger
Layer
TRIGger
:DIRection
ACCeptor
TRIGger:SOURce IMMediate Trigger-In
TRIGger:SOURce TLINk
Source

TRIGger:DELay
TRIGger:DELay:AUTO
0.0 sec
Note: The following commands place the
Model 6487 into idle: ABORt,
*RST, SYSTem:PRESet, *RCL ,
DCL, and SDC.

Trigger Event
Detector

Trigger Delay

SOURce

No
Yes

Another
Trigger
?

TRIGger:OUTPut

TRIGger:COUNt

SENSe | NONE

MEASURE
Action
= Output Trigger

The difference between front panel operation (Figure 7-1) and remote operation
(Figure 7-2) is within the idle state of the instrument. Nomenclature in Figure 7-1 relates
to the various names used for configuration menu items while Figure 7-2 provides the
SCPI commands to control operation.

7-4

Triggering

Model 6487 Reference Manual

Idle and initiate
While in the idle state, the instrument cannot perform measurements. While in idle, the
reading remains frozen or dashes replace the reading (i.e. -.------ A). Once the Model 6487
is taken out of idle, operation proceeds through the trigger model.
Front panel operation — As shown in Figure 7-1, the Model 6487 immediately leaves
the idle state when it is turned on. Typically, operation remains in the arm and trigger
layers of the trigger model. However, the Model 6487 can be put into the idle state at any
time by selecting HALT in the trigger configuration menu. To take the instrument out of
idle, press the TRIG key. Other front panel keys can be pressed instead, but they may
change the setup.
Remote operation — As shown in Figure 7-2, an initiate command is required to take the
instrument out of idle. The following commands perform an initiate operation:
•
•
•

INITiate
READ?
MEASure?

While operating within the trigger model (not in idle), most commands will not be executed until the instrument completes all of its programmed operations and returns to the
idle state. The IFC, SDC, and DCL commands can be executed under any circumstance
while operating within the trigger model. They will abort any other command or query.
The following commands can be executed while operating within the trigger model except
when a READ? or MEASure? is being processed:
•
•
•
•
•
klqb

ABORt
SYSTem:PRESet
*TRG or GET
*RST
*RCL
For fastest response, use SDC or DCL to return to idle (see Section 9 for details
on general bus commands).

Model 6487 Reference Manual

Triggering

7-5

Trigger model operation
Once the instrument is taken out of idle, operation proceeds through the trigger model to
perform a measurement (measure action).
klqb

The following discussion focuses on the front panel trigger model (Figure 7-1).
However, equivalent SCPI commands are included where appropriate.

Event detectors and control sources
A control source holds up operation until the programmed event occurs and is detected.
Note that there are two detector bypasses. A bypass around a detector is only enabled if the
appropriate TLink control source is selected. See TLink control source (Arm-In and Trigger-In) as follows for details.
Arm-In source — The Arm-In control sources are explained as follows:
•
•
•

•

Immediate (ARM:SOURce IMMediate) — Event detection for the arm layer is
satisfied immediately allowing operation to continue into the trigger layer.
GPIB (ARM:SOURce BUS) — Event detection for the arm layer is satisfied when
a bus trigger (GET or *TRG) is received by the Model 6487.
Timer (ARM:SOURce TIMer) — Event detection for the arm layer is immediately
satisfied after the instrument leaves the idle state. Detection for each subsequent
pass is satisfied when the programmed timer interval elapses. The timer resets to its
initial state when the instrument goes back into idle.
Manual (ARM:SOURce MANual) — Event detection for the arm layer is satisfied
by pressing the TRIG key. The Model 6487 must be in the local mode for it to
respond to the TRIG key. Press LOCAL or send LOCAL 14 over the bus to place
the Model 6487 in local.
TLink (ARM:SOURce TLINk) — Event detection for the arm layer is satisfied
when an input trigger via the TRIGGER LINK connector is received by the
Model 6487. Note that if the source bypass is set to ONCE (ARM:DIRection
SOURce), operation will initially loop around the source detector after the instrument leaves the idle state. Detection for each subsequent pass is satisfied by an
input trigger. The bypass resets when the instrument goes into idle.
/STest (ARM:SOURce NSTest) — Event detection for the arm layer is satisfied
when a negative-going pulse (via the SOT line of the Digital I/O) is received from a
component handler (see Limit Tests and Digital I/O in Section 8).
STest (ARM:SOURce PSTest) — Event detection for the arm layer is satisfied
when a positive-going pulse (via the SOT line of the Digital I/O) is received from a
component handler (see Limit Tests and Digital I/O in Section 8).
BSTest (ARM:SOURce BSTest) — Event detection for the arm layer is satisfied
when either a positive-going or a negative-going pulse (via the SOT line of the Digital I/O) is received from a component handler (see Limit Tests and Digital I/O in
Section 8).

7-6

Triggering

Model 6487 Reference Manual

Trigger-In source — The Trigger-In control sources are explained as follow:
•

•

Immediate (TRIGger:SOURce IMMediate) — Event detection for the trigger
layer is satisfied immediately allowing operation to continue to perform a
measurement.
TLink (TRIGger:SOURce TLINk) — Event detection for the trigger layer is satisfied when an input trigger via the TRIGGER LINK connector is received by the
Model 6487. Note that if the source bypass is set to ONCE (TRIGger:DIRection
SOURce), operation will loop around the source detector on the initial pass
through the arm layer. Detection for each subsequent pass is satisfied by an input
trigger. The bypass resets when the Model 6487 leaves the trigger layer.

Trigger delay
A programmable delay is available after event detection. It can be set manually (0 to
999.9998 seconds) or an auto delay can be used. With auto delay selected, the Model 6487
automatically sets delay according to range. The auto delay settings are listed in Table 7-1.
Table 7-1
Auto delay settings
Range
2nA
20nA
200nA
2μA
20μA
200μA
2mA
20mA

Delay
10ms
10ms
10ms
10ms
5ms
5ms
1ms
0.5ms

Model 6487 Reference Manual

Triggering

7-7

Measure action
The measure action block of the trigger model is where a measurement is performed.
However, if the repeating filter is enabled (Figure 7-3), the instrument samples the specified number of reading conversions to yield single filtered reading. Only one reading conversion is performed if the digital filter is disabled or after the specified number of reading
conversions for a moving average filter is reached.
If a voltage sweep is active, one measure action per voltage step is performed.
Figure 7-3
Measure action block of trigger model
Measure Action

Filter Process (Repeat)

CONV

CONV = Reading Conversion

Output triggers
The Model 6487 can send out an output trigger (via the rear panel TRIGGER LINK
connector) right after the measure action and/or when operation leaves the trigger layer.
An output trigger can be used to trigger another instrument to perform an operation
(e.g., select the next output step for a source).

Counters
Programmable counters are used to repeat operations within the trigger model layers. For
example, if the trigger count is set for 10, operation will keep looping around in the trigger
layer until 10 measurements are performed. If the arm count is set to 2, operation will then
loop back through the arm layer and go back into the trigger layer to perform 10 more
measurements.

7-8

Triggering

Model 6487 Reference Manual

Trigger model configuration — front panel
klqb

See “SCPI Programming” (Table 7-3) for the SCPI commands to configure the
trigger model over the bus.

Press CONFIG and then TRIG to configure both the TRIG and ARM layers of the trigger
model.
klqb

When done configuring the trigger level, press ENTER to confirm value and then
use the EXIT key to save changes and leave trigger model configuration.

Once in trigger model configuration mode, use the RANGE keys to display either the
TRIGGER layer or the ARM layer menus. Press ENTER to select the desired menu. Then
use the RANGE keys to display menu items. Use the cursor keys to key in values. A menu
item or value is selected by pressing ENTER. Use the EXIT key to exit from the menu
(saving all changes made).
Table 7-2
Trigger model menu structure
Menu
CONFIG
- TRIG

Description
Path to TRIG and ARM menus. Access by pressing
CONFIG and then TRIG.
Path to TRIG layer sub-menus.

- - COUNT
- - - INF
- - - FIN

Set TRIG measure count.
Specify an INFinite measure count.
Specify a FINite measure count: 1–2048.

- - DELAY
- - - MAN
- - - AUTO

Set trigger delay.
Specify trigger delay: 0–999.9998 sec.
Enable auto delay.

TRIG-OUT
- LINE
- - TLINK
- EVENTS
- - VMC

Configure output triggers.
Select the output trigger link line.
Set trigger link value: 1–6.
Select VMC (voltmeter complete) output trigger.
Enable/disable VMC (on or off).

TRIG-IN
- SOURCE
- - IMM
- - TLINK
- - - TLINK
- - - EVENT

Path to control source.
Set the TRIG-IN control source.
Set control source to IMMediate.
Set control source to TLINK.
Set TLINK value: 1–6.
Enable (set to ONCE) or disable (set to NEVER).

Model 6487 Reference Manual

Triggering

7-9

Table 7-2 (cont.)
Trigger model menu structure
Menu

Description

- HALT

Stops triggering. Press TRIG to resume.

- ARM

Path to ARM layer submenus.

ARM-IN
- IMM
- GPIB
- TIMER

ARM-OUT
- LINE
- - TLINK
- EVENT
- - T - L - DONE

MAN
TLINK
- TLINK
- EVENT
/STEST
STEST
BSTEST

- - COUNT
- - - INF
- - - FIN

klqb

Path to ARM-IN control source.
Set control source to IMMediate.
Set control source to GPIB.
Set control source to TIMER. Set timer from
0.001S to 27H, 46M, and 39.992S.
Set control source to MANual.
Set control source to TLINK.
Set TLINK value: 1–6.
Enable (set to ONCE) or disable (set to NEVER).
Set control to negative pulse on SOT line (Section 8).
Set control to positive pulse on SOT line (Section 8).
Set control to positive or negative pulse on SOT line
(Section 8).
Path to ARM-OUT trigger.
Set the output trigger link line.
Set trigger link value: 1–6.
Set Trigger Layer Done event.
Enable/disable Trigger Layer Done (on / off).
Set ARM measure count.
Specify an INFinite measure count.
Specify a FINite measure count: 1–2048.

Input trigger and output triggers cannot share the same trigger link line.
Defaults set line 1 as the input and line 2 as the output.

7-10

Triggering

Model 6487 Reference Manual

SCPI programming
Table 7-3
SCPI commands — triggering
Command
ABORt
INITiate
FETCh?
READ?
ARM[:SEQuence[1]]
[:LAYer[1]]
:SOURce
:COUNt
:TIMer
[:TCONfigure]
:DIRection
[:ASYNchronous]
:ILINe
:OLINe
:OUTPut
TRIGger
:CLEar
[:SEQuence[1]]
:SOURce
:COUNt
:DELay
:AUTO
[:TCONfigure]
:DIRection
[:ASYNchronous]
:ILINe
:OLINe
:OUTPut

Description

Default

Reset trigger system (goes to idle state).
Initiate one trigger cycle.
Request latest reading.
Trigger and request a “fresh” reading.
Arm Layer:

Ref
A
B
B
B

Select control source: IMMediate, TIMer, BUS,
MANual, TLINk, PSTest, NSTest, or BSTest.
Set measure count: 1 to 2048, or INF (infinite).
Set timer interval: 0.001 to 99999.999 (sec).

IMM

Enable (SOURce) or disable (ACCeptor) bypass.
Configure input/output triggers:
Select input trigger line: 1, 2, 3, 4, 5, or 6.
Select output trigger line: 1, 2, 3, 4, 5, or 6.
Output trigger (TRIGger) or not at all (NONE).
Trigger Layer:
Clear pending input trigger immediately.
Trigger path.
Select control source: IMMediate or TLINk.
Set measure count: 1 to 2048 or INF (infinite).
Set trigger delay: 0 to 999.9998 (sec).
Enable or disable auto delay.

ACC

1
2
NONE

E
E

1
0.1

F
IMM
1
0.0
OFF
ACC

1
2
NONE

E
E

A) ABORt
If operation has been started by the INITiate command, ABORt will cancel all operations
and immediately return the instrument to the idle state. If operation has been started by
READ? (or MEASure?), ABORt has no effect.

Model 6487 Reference Manual

Triggering

7-11

B) INITiate, FETCh, and READ?
1.

2.
3.

After sending the INITiate command to take the instrument out of idle, the instrument will perform one or more measurements and then return to idle. The FETCh?
command can then be used to read the last reading that was measured.
If INITiate is sent while the instrument is operating within the trigger model, it will
not execute until the operation returns to the idle state.
One alternative to using INITiate is to use the READ? command. When READ? is
sent, the instrument is taken out of idle and all readings that are taken are returned
(See Section 12 for details on READ?).

C) ARM:SOURce
With the TIMer control source selected, use the ARM:TIMer command to set the timer
interval.

D) ARM:DIRection
The source bypass can only be used if the TLINk control source is selected.

ARM:ILINe and ARM:OLINe

Input trigger and output trigger cannot share the same trigger link line. Defaults set line 1
as the input and line 2 as the output.

TRIGger:CLEar

When this action command is sent, any pending (latched) input triggers are cleared immediately. When the picoammeter is being latched by another instrument, it may inadvertently receive and latch input triggers that do not get executed. These pending triggers
could adversely affect subsequent operation.
When using external triggering, it is recommended that TRIGger:CLEar be sent after
sending the ABORt command and at the beginning of a program before sending a initiate
command. (See “INITiate” command.)

Programming example
The following command sequence will trigger and return 10 readings.
*RST
ARM:SOUR IMM
ARM:COUN 1
TRIG:SOUR IMM
TRIG:COUN 10
SYST:ZCH OFF
READ?

'
'
'
'
'
'
'

Return 6487 to RST defaults.
Set arm control source Immediate.
Set arm count to 1.
Set trigger control source Immediate.
Set trigger count to 10.
Disable zero check.
Trigger and return 10 readings.

7-12

Triggering

Model 6487 Reference Manual

External triggering
Input and output triggers are received and sent via the rear panel TRIGGER LINK connector. The trigger link has six lines. At the factory line #2 is selected for output triggers and
line #1 is selected for input triggers. These input/output assignments can be changed as
previously explained in this section. The connector pinout is shown in Figure 7-4.
Figure 7-4
Trigger link connection operation
Rear Panel Pinout

8
5

7 6
4 3
2 1

Trigger Link

Pin Number

Description

Trigger Link 1

Trigger Link 2

Trigger Link 3

Trigger Link 4

Trigger Link 5

Trigger Link 6

Ground

Input trigger requirements
An input trigger is used to satisfy event detection for a trigger model layer that is using the
TLINK control source. The input requires a falling-edge, TTL-compatible pulse with the
specifications shown in Figure 7-5.
Figure 7-5
Trigger link input pulse specifications
Triggers on
Leading Edge
TTL High
(2V-5V)

TTL Low
(<0.8V)
2 μs
Minimum

Model 6487 Reference Manual

Triggering

7-13

Output trigger specifications
The Model 6487 can be programmed to output a trigger immediately after a measurement
and/or when operation leaves the trigger layer of the trigger model. The output trigger provides a TTL-compatible output pulse that can be used to trigger other instruments. The
specifications for this trigger pulse are shown in Figure 7-6. A trigger link line can source
1mA and sink up to 50mA.
Figure 7-6
Trigger link output pulse specifications
Meter Complete

TTL High
(3.4V Typical)
TTL Low
(0.25V Typical)
5μs
Minimum

External trigger example
In a simple test system, you may want to close a switching channel and measure the current from a DUT connected to that channel. Such a test system is shown in Figure 7-7.
This example uses a Model 6487 to measure 10 DUTs switched by a Model 7158 low current card in a Model 7001 or 7002 switch system.
Figure 7-7
DUT test system
OUTPUT

DUT
#1

LO
DUT
#2

CAT I
MADE IN
U.S.A.

IEEE-488

(CHANGE IEEE ADDRESS
WITH FRONT PANEL MENU)

ANALOG OUT

INPUT

Model 6487
Picoammeter
RS-232

TRIGGER LINK
RANGE
DEPENDENT

DUT
#10
7158 Low Current Card

LINE RATING
50, 60Hz
30 VA

FUSE

LINE

630mAT
(SB)

100 VAC
120 VAC

315mAT
(SB)

220 VAC
240 VAC

120

DUT
#3-#9

Triggering

Model 6487 Reference Manual

The trigger link connections for this test system are shown in Figure 7-8. The trigger link
of the Model 6487 is connected to the trigger link (IN or OUT) of the switching mainframe. Note that with the default trigger settings of the switching mainframe, line #1 is an
input and line #2 is an output.
Figure 7-8
Trigger link connections
7001 or 7002 Switch System

Model 6487 Picoammeter
MADE IN
U.S.A.

CAT I

IEEE-488

ANALOG OUT

(CHANGE IEEE ADDRESS
WITH FRONT PANEL MENU)

DIGITAL I/O

!
505V PK
505V PK
505V PK

MADE IN USA

TRIGGER LINK

INPUT

IN
OUT

Trigger
Link

RS-232

V-SOURCE OUTPUT
505V PK TO CHASSIS
LO
505V
MAX

Trigger Link Cable
(8501)

HI INTERLOCK

120

7-14

FUSE

LINE

400mAT
(SB)

100 VAC
120 VAC

200mAT
(SB)

220 VAC
240 VAC

LINE RATING
50, 60Hz
50 VA MAX

Trigger
Link

For this example, the Model 6487 and switching mainframe are configured as follows:
Model 6487
Factory Defaults Restored
Trig-In Event = TLink
Trigger Input Line = #2
Trigger Output Line = #1
Trigger Output Event = ON
Trigger Count = 10
Trigger Delay = Auto

Switching Mainframe
Factory Defaults Restored
Scan List = 1!1-1!10
Number of Scans = 1
Channel Spacing = TrigLink

To store readings in the Model 6487 buffer, first set the number of points to store in the
buffer:
1.
2.
3.
4.

Press CONFIG and then STORE.
Set the buffer size to 10 using the RANGE and cursor keys.
Press ENTER.
The next time STORE is pressed, the asterisk (*) annunciator turns on to indicate
the buffer is enabled. (See the Model 6487 User’s Manual for buffer details.)

To start the test, press STEP on the switching mainframe to take it out of idle and start the
scan. The switching mainframes output pulse triggers the Model 6487 to take a reading
and store it. the Model 6487 then sends an output trigger pulse to the switching mainframe
to close the next channel. This process continues until all 10 channels are scanned, measured, and stored.

Model 6487 Reference Manual

Triggering

7-15

Figure 7-9
Operation model for triggering example
7001or 7002
Press STEP to start scan
Idle
Bypass

6487
Idle

Wait for
Trigger Link
Trigger

Scan
Channel

Output
Trigger

Scanned
10
Channels
?
Yes

Wait for
Trigger Link
Trigger
Make
E
Measurement

Trigger

Output
Trigger

Made
10
No
Measurements
?
Yes

Details of this testing process are explained in the following paragraphs and are referenced
to the operation model shown in Figure 7-9.
A.
B.
C.
D.

E. and F.

Operation of the Model 6487 starts at point A in the flowchart where it waits for
an external trigger.
Pressing STEP takes Model 7001/7002 out of idle and places operation at point
B in the flowchart.
For the first pass through Model 7001/7002, the scanner does not wait at point
B. Instead, it closes the first channel (point C).
After the relay settles, Model 7001/7002 outputs a trigger pulse. Since the
instrument is programmed to scan 10 channels, operation loops back to point B
where it waits for an input trigger.
With the Model 6487 at point A, the output trigger pulse from Model 7001/7002
triggers a measurement of DUT #1 (point E). After the measurement is complete, the Model 6487 outputs a trigger pulse and then loops back to point A
where it waits for another input trigger.

7-16

Triggering

Model 6487 Reference Manual

The trigger applied to Model 7001/7002 from the Model 6487 closes the next channel in
the scan, which then triggers the Model 6487 to measure that DUT. This process continues
until all 10 channels are scanned and measured.

Limit Tests and Digital I/O
•

Limit testing — Explains the basic Limit 1 and Limit 2 testing operations.

•

Binning — Explains how to use a component handler to perform binning
operations.

•

Digital I/O port — Explains how to use the digital I/O port to control external
circuitry.

•

Front panel operation — limit tests — Explains how to configure and run limit
tests from the front panel.

•

SCPI programming — limit tests — Covers the SCPI commands for remote limit
test operation.

8-2

Limit Tests and Digital I/O

Model 6487 Reference Manual

Limit testing
As shown in Figure 8-1, there are two limit tests that can be performed on a DUT. Limit 1
is used as the wide pass band and Limit 2 is used as the narrow pass band. It is up to the
user to specify limits that conform to this pass band relationship.
Figure 8-1
Limit tests
LO

Fail

Pass

Fail

Limit

Limit 1 Test
(Wide Pass Band)

Limit
LO

Fail

HI
Pass

Limit

Fail

Limit 2 Test
(Narrow Pass Band)

Limit

Figure 8-2 shows an example where the HI and LO limits for Limit 1 are ±2mA and the HI
and LO limits for Limit 2 are ±1mA. A 0mA reading passes both Limit 1 and Limit 2 tests.
A +1.5mA reading passes Limit 1 but fails Limit 2. A +2.5mA reading fails both Limit 1
and Limit 2.
Figure 8-2
Limit tests example
-2mA

+2mA

Fail

Pass

Fail
HI Limit

LO Limit
+1mA

-1mA
Fail

Pass
LO Limit

Limit 1 Test
(Wide Pass Band)

Fail
HI Limit

Limit 2 Test
(Narrow Pass Band)

Model 6487 Reference Manual

Limit Tests and Digital I/O

8-3

The 2-stage limit testing process is shown in . If Limit 1 fails, the L1 message is displayed
and the test is finished. Limit 2 is not tested because the pass band relationship between
the two stages implies that if Limit 1 fails, Limit 2 must also fail. If Limit 1 passes, the
Limit 2 test is performed. If Limit 2 fails, the L2 message is displayed. If both Limit 1 and
Limit 2 pass, the OK message is displayed. The display messages for limit tests are summarized in Table 8-1.
klqb

When limit tests are enabled, the voltage source value display is not visible, but
it can still be viewed by using the CONFIG V-SOURCE menu or by pressing the
V-SOURCE up or down arrow keys.
Table 8-1
Test limit display messages
Display
Message

Limit 1
Test Result

Limit 2
Test Result

:OK

Pass

:L1

Fail

Not Performed

:L2

Pass

Fail

A test is only performed if it is enabled. Therefore, you can perform a single-stage test or a
2-stage test. In the flowchart (), operation simply proceeds through a disabled test.

8-4

Limit Tests and Digital I/O

Model 6487 Reference Manual

Figure 8-3
Operation model for limit test
Start
Measure
DUT
Limit 1
Test

Pass
?

Display
“L1”

Display
“L2”

Yes
Limit 2
Test

Pass
?
Yes
Display
“OK”

End

klqb

Display messages indicate which test or tests have failed, but they do not
indicate which limit (HI or LO) has failed. When using remote operation, you
can determine which limit failed by reading the measurement event register. See
Ref C for the FAIL? commands in Table 8-3 on page 8-18.
Relative (Rel), mX+b, m/X+b, and log can be used with limit testing. The tests
will be done on the result of the math operation (not the input values). These
math operations are covered in Section 5.

Application — A typical application for a 2-stage limit test is to sort a batch of DUT
according to tolerance. For example, you may want to sort diodes (all having the same
nominal value) into three groups, 1%, 5%, and >5%. The limits for Limit 1 would be the
5% tolerances and the limits for Limit 2 would be the 1% tolerances. If a diode passes both
tests, it belongs in the 1% group. If it passes Limit 1 but fails Limit 2, it belongs in the 5%
group. If it fails both tests, it belongs in the >5% group.

Model 6487 Reference Manual

Limit Tests and Digital I/O

8-5

Binning
Even though no additional equipment is required to perform limit tests on the DUT, the
Model 6487 can be used with a component handler to perform binning operations. Based
on the outcome of a test, the component handler will place the DUT in the assigned bin.
Figure 8-4 shows a basic binning system. After all programmed testing on the DUT is
completed, the appropriate digital output pattern is sent to the component handler, which
then places the DUT in the appropriate bin. The component handler selects the next DUT
and the testing process is repeated.
Figure 8-4
Binning system
Handler
Dig
In
DUT

Input
HI

LO
Dig
I/O
6487

8-6

Limit Tests and Digital I/O

Model 6487 Reference Manual

Figure 8-5 shows the basic limit testing flowchart expanded to include binning. Notice
that there are five possible output patterns (one pass pattern and four fail patterns), but
only one will be sent to the component handler for each DUT that is tested.
Figure 8-5
Operation model for limit testing with binning
Start
Measure
DUT

Limit 1
Test

Pass
?

HI Limit
Failure
No

Display
“L1”

Yes

Output Fail
Pattern

Which
Limit
Failed
?

LO Limit
Failure

Output Fail
Pattern

Limit 2
Test
HI Limit
Failure
Pass
?

Yes
Display “OK” and
Output Pass Pattern

Yes

Test
Another
DUT
?
No
End

Display
“L2”

Output Fail
Pattern

Which
Limit
Failed
?

LO Limit
Failure

Output Fail
Pattern

Model 6487 Reference Manual

Limit Tests and Digital I/O

8-7

Component handler interface
The Model 6487 is interfaced to a component handler via the Digital I/O port as shown in
Figure 8-6. (See “Digital I/O port,” page 8-11 for more information.) The I/O port has four
lines for output signals and one line for input signals. The input line is used to start the test
and the output lines are used to send the test pass/fail signal(s) to the component handler to
perform the binning operation.
Figure 8-6
Handler interface connections
6487

Handler

Out 1
Out 2
Out 3
Out 4

Line 1
Line 2
Line 3
Line 4 (or EOT)
Relay Clamp Voltage
V External

Dig I/O

Input (SOT)

Gnd
SOT Strobe Line

The digital I/O lines are available at the DB-9 connector on the rear panel of the
Model 6487. A custom cable using a standard female DB-9 connector is required for connection to the Model 6487.

Start of test
The SOT (start of test) line of the Digital I/O is used to control the start of the testing process. When /STest is the selected arm-in event for the arm layer of the trigger model, the
testing process will start when the SOT line is pulled low. When STest is the selected
arm-in event, the test will start when the SOT line is pulled high. When BSTest is the
selected arm-in event, the test will start when the SOT line is pulled either high or low.
Section 7 provides details on trigger model configuration.
klqb

If you do not wish to use the SOT line to start the test, you can use the immediate
arm-in event. The testing process will start as soon as the LIMIT key is pressed
(assuming one or both limit tests are enabled).

The component handler will either maintain the SOT line high or low. This is its “not
ready” condition. When the component handler is ready (DUT properly position in the
handler), it will either pull the SOT line low or high to start the test.

8-8

Limit Tests and Digital I/O

Model 6487 Reference Manual

Digital output patterns
The Model 6487 uses digital output bit patterns to communicate test results to the component handler. For each limit test, unique fail patterns are used for the HI and LO limits. A
pass pattern is used to indicate that there were no errors. After a test is finished, the appropriate output pattern is sent to the component handler. The handler decodes the bit pattern
and places the DUT in the appropriate bin.
The Model 6487 can be used with either of the two basic types of handlers. When used
with a category pulse handler, the Model 6487 pulses one of the four handler lines. The
handler then places the DUT into the bin assigned to the pulsed line.
When used with a category register handler, the Model 6487 outputs a bit pattern to three
handler lines. After the Model 6487 sends the end-of-test (EOT) strobe pulse to the fourth
handler line, the handler places the DUT into the bin assigned to that bit pattern.

Component handler types
The Model 6487 can accommodate two different types of component handlers: category
pulse and category register.

Category pulse component handler
When using this type of handler, the Model 6487 pulses one of the four handler lines when
a pass or fail condition occurs. The handler then places the DUT in the bin assigned to that
pulsed line. When interfacing to this type of handler, a maximum of four component
handler bins are supported.
If the handler requires low-going pulses, then the four digital output lines of the
Model 6487 must be initially set to high. This initial HI, HI, HI, HI clear pattern on the
output lines represents a “no action” condition for the handler since it is waiting for one of
the lines to go low. A line goes low when the defined fail or pass pattern sets it low. For
example, if you want a particular test failure to pulse line #4 of the handler, the defined fail
pattern has to be HI, HI, HI, LO. When the failure occurs, line #4 will be pulled low and
the DUT will be placed in the bin assigned to that pulsed line.
If the handler requires a high-going pulse, the four digital output lines of the Model 6487
must initially be set low. The LO, LO, LO, LO clear pattern represents the “no action”
condition for the handler. When one of those lines are pulled high by a defined pass or fail
bit pattern (i.e., LO, LO, LO, HI), the DUT will be placed in the bit assigned to that pulsed
line.

Model 6487 Reference Manual

Limit Tests and Digital I/O

8-9

Category register component handler
When using this type of handler, the Model 6487 sends a bit pattern to three handler lines
when a pass or fail condition occurs. This bit pattern determines the bin assignment for the
DUT. With the pass/fail pattern on the output, line #4 is then pulsed. This EOT (end-oftest) pulse latches the bit pattern into the register of the handler, which places the DUT in
the assigned bin. When interfacing to this type of handler, a maximum of eight component
handler bins are supported.
If the handler requires a low-going EOT pulse, line #4 of the digital output must initially
be set high. When the EOT line is pulsed low, the binning operation occurs. When using
the CONFIG LIMITS MENU to define pass/fail bit patterns, line #4 must be set low. If,
for example, the required fail pattern by the handler is HI, LO, HI, then you must define
the fail pattern of the test to be HI, LO, HI, LO. When the test fails, the HI, LO, HI bit pattern is sent to the handler. When line #4 goes LO, the bit pattern is latched into the register
of the handler and the binning operation occurs.
Conversely, if the handler requires a high-going EOT pulse, the EOT line of the digital
output must initially be set low (off). When the EOT line is pulsed high, the binning operation occurs.

Line 4 mode
When using a category pulse component handler, the Model 6487 must be set to the Busy
or /Busy mode. In the Busy mode, the idle state for line 4 is LO. When the test starts (SOT
line pulsed), line 4 goes HI (busy state). After the test is finished, it goes back to LO. For
the /Busy mode, the idle state for line 4 is HI and busy state is LO.
When using a catagory register component handler, the Model 6487 must be set for the
End of Test mode. In this mode, the Model 6487 sends the EOT pulse to the component
handler as previously explained.

8-10

Limit Tests and Digital I/O

Model 6487 Reference Manual

Digital output clear pattern
After every binning operation, the digital output needs to be reset to a clear pattern, which
serves as a “no action” condition for the component handler.
The Model 6487 can be programmed to automatically clear the digital output after the
pass or fail pattern is sent. With auto-clear, you must specify the required pulse width
(delay) for the pass or fail pattern. When not using auto-clear, you must return the digital
output to its clear pattern.
klqb

With the Busy line 4 mode selected, the clear state of line 4 is LO, regardless of
the configured clear pattern. With the /Busy mode selected, the clear state of line
4 is HI.

Auto-Clear timing — The following example timing diagram (Figure 8-7) and discussion
explain the relationship between the digital output lines for auto-clear.
Figure 8-7
Digital output auto-clear timing example
SOT*
Line 1

Line 2
Line 3

Line 4
(EOT)

10μs

Delay

10μs

* With the SOT line being pulsed low (as shown), /START TEST must be the selected
arm event for the trigger model. If the SOT line is instead pulsed high by the
handler, START TEST must be the selected arm event.

Initially, the four digital output lines are cleared (in this case, they are all set high). Limit
tests start when the Start-Of-Test (SOT) pulse is received from the component handler.
When the testing process is finished, the pass or fail pattern is applied to the digital output.
As shown in the diagram, lines 2, 3, and 4 go low while line 1 remains high.
The pulse width (delay) of the pass/fail pattern can be set from 0 to 60 sec (10µsec resolution) as required by the component handler. Note that the delay specifies the pulse width
of line 4. The pulse width of lines 1, 2, and 3 is actually 20µsec longer. Line 4 is skewed
because it is used as the End-Of-Test (EOT) strobe by category register component han-

Model 6487 Reference Manual

Limit Tests and Digital I/O

8-11

dlers. Lines 1, 2, and 3 establish the bit pattern and then 10µsec later the SOT strobe
“tells” the handler to read the bit pattern and perform the binning operation. This 10µsec
offset is used to make sure the correct bit pattern is read by the handler.
After the pass/fail is read by the handler, the digital output returns to the clear pattern.

Digital I/O port
The Model 6487's Digital I/O port is a male DB-9 connector located on the rear panel. The
port location and pin designations are shown in Figure 8-8. The four active-low, digital
output lines and one input line are used to control external circuitry.
Figure 8-8
Digital I/O port
Model 6487 Picoammeter
MADE IN
U.S.A.

CAT I

IEEE-488

ANALOG OUT

(CHANGE IEEE ADDRESS
WITH FRONT PANEL MENU)

DIGITAL I/O

!
505V PK
505V PK
505V PK
TRIGGER LINK

INPUT

RS-232

V-SOURCE OUTPUT
505V PK TO CHASSIS

1=
2=
3=
4=
5=
6=
7=
8=
9=

HI INTERLOCK
505V
MAX

120

FUSE

LINE

400mAT
(SB)

100 VAC
120 VAC

200mAT
(SB)

220 VAC
240 VAC

Digital Output #1
Digital Output #2
Digital Output #3
Digital Output #4 (EOT*)
VEXT
SOT*
Not Used
Not Used
Digital Ground

LINE RATING
50, 60Hz
50 VA MAX

1 2 3 4 5

6 7 8 9

DIGITAL I/O

*Start of Test (SOT) and End of Test
(EOT) are used for Limit Tests.

Typical applications for the digital I/O port include the following:
•

Component handler control — When performing limit tests, a component handler can be used to sort DUT into bins. (See “Binning,” page 8-5 for details.) The
digital I/O of the Model 6487 serves as the interface between the limit tests and the
component handler. Via the digital input line (pin 6), the component handler can
tell the Model 6487 when it is ready for the test. Via the digital output lines, The
Model 6487 sends digital output patterns to the component handler and tells it
when the test is finished. A digital output pattern determines which bin the DUT
belongs in.

8-12

Limit Tests and Digital I/O

•

Model 6487 Reference Manual

External device control — Each digital output can be used as a control switch for
an external device (i.e. relay) circuit. Each output line can sink up to 500mA. Drive
voltage is provided by an external source (+5V to +33V).
Logic Control — The four digital outputs can be used as inputs to logic devices.

The simplified schematic for the digital outputs is shown in Figure 8-9. Note that this
illustration shows the schematic for one digital output. All four digital output circuits are
identical.
Figure 8-9
Digital I/O port simplified schematic
Pin 5 - External Voltage Flyback
connection (+5V to +33V)
+5V
Digital Output
Flyback Diode
1kΩ (Pull-up)

Digital Output
Protection
Diode
Pin 9 - Digital Ground

Sink mode — controlling external devices
Each output can be operated from an external supply (voltage range from +5V to +33V
applied through the external device being driven). The high current sink capacity of the
output driver allows direct control of relays, solenoids, and lamps (no additional circuitry
needed).
As shown in Figure 8-9, each of the four digital, open-collector outputs includes a built-in
pull up resistor to +5V. The output transistor is capable of sinking 500mA from voltages
up to +33V. Each output channel contains a fly-back diode for protection when switching
inductive loads (such as a low power solenoid or relay coils). To use these fly-back diodes,
connect the external supply voltage to pin 5 of the digital I/O port. Make sure the external
supply voltage is between +5V and +33V and the current required by the device does not
exceed 500mA.

Model 6487 Reference Manual

`^rqflk

Limit Tests and Digital I/O

8-13

Do not exceed +33V maximum voltage on pin 5 of the digital I/O port
and do not use any output line to sink >500mA. Exceeding these limits
may cause damage to the instrument that is not covered by the
warranty.

An externally powered relay connected to the digital output port is shown in Figure 8-10.
Other externally powered devices can be similarly connected by replacing the relay with
the device. When the output line is set LO (0V), the output transistor sinks current through
the external device. In the HI state, the output transistor is off (transistor switch open).
This interrupts current flow through the external device.
Figure 8-10
Controlling externally powered relays
Model 6487
Pin 5 - External Voltage Flyback Connection

To three other
digital outputs
+5V
Digital Output #1
Flyback Diode

Relay
Coil

1kΩ
Pull Up
Resistor

(+)
(-)

External Power
(+5V to +33V)

Pin 1 - Digital Output #1

Pin 9 - Digital Ground

Equivalent Circuit

Flyback
Diode

Relay
Coil

(+)
(-)

External Power
(+5V to +33V)
Transistor
Switch

8-14

Limit Tests and Digital I/O

Model 6487 Reference Manual

Source mode — logic control
The digital outputs can be used as logic inputs to active TTL, low-power TTL, or CMOS
inputs. For this mode of operation, the output lines can source up to 2mA.
`^rqflk

Each output line can source up to 2mA. Exceeding 2mA may cause
damage to the Model 6487 that is not covered by the warranty.

Figure 8-11 shows how to connect a logic device to one of the output lines. When the output line is set HI, the transistor will turn off (transistor switch open) to provide a reliable
logic high output (>3.75V). When the output line is set LO, the transistor turns on (transistor switch closed) to route current to digital ground. As a result, a low logic output (0V) is
provided at the output.
If the second input (B) of the NAND gate is connected to another output line of the port,
the output of the NAND gate will go to logic 0 when both digital outputs are set HI.
Figure 8-11
NAND gate control
Model 6487
+5V
Logic
Device

1kΩ
Pull Up
Resistor

B
NAND

Pin 1
A

Pin 9

Setting digital output lines
Digital output lines are set by selecting a decimal value (0 to 15) that corresponds to the
4-bit BCD pattern of the output. To determine the value, add up the decimal weight values
for the desired HI lines:
Output HI Line:

Out 4

Out 3

Out 2

Out 1

Decimal Weight:

Model 6487 Reference Manual

Limit Tests and Digital I/O

8-15

For example, to set output lines 3 and 1 HI (0101 bit pattern), set the output value to
5 (4 +1).
Perform the following steps to set the digital output pattern from the front panel:
1.
2.
3.
4.
5.

Press CONFIG and then LIMIT to access the limits menu.
Press the cursor keys until “LIMIT:PASS” is displayed.
Press ENTER. The present digital output pattern value will be displayed.
Use the cursor and RANGE keys to display the desired output pattern value (0 to
15), and press ENTER.
Press EXIT to return to the normal display state.

SCPI programming — digital output pattern
Table 8-2
SCPI commands — digital outputs
Command

Description

Default

:TTL |

Specify 4-bit digital output pattern (see “Parameter Values” below).

:TTL?

Query the digital output pattern. The value returned is in the
decimal format.

:SOURce2

SOURce2 Subsystem:

Parameter Values (see Note):

= 0 to 15

Decimal format

= #Bxxxx
= #Hx
= #Qxx

Binary format (each x = 1 or 0)
Hexadecimal format (x = 0 to F)
Octal format (x = 0 to 17)

Note: The parameter type can be used to set the output pattern using non-decimal values. Convert the decimal value to its
binary, hexadecimal, or octal equivalent and include the appropriate header (#B, #H, or #Q). For example, to set output lines 4
and 2 HI using the binary format, send SOURce2:TTL #B1010.

Programming example
The following command sequence sets output lines 4 and 2 HI and output lines 3 and
1 LO.
SOUR2:TTL 10
SOUR2:TTL?

' Set output lines 4 and 2 HI.
' Request output pattern value.

8-16

Limit Tests and Digital I/O

Model 6487 Reference Manual

Front panel operation — limit tests
Limit test configuration
Most aspects of limit testing are configured from the limit configuration menu. Once in a
menu structure, use the cursor keys to display menu items. Use the cursor keys to key in
values. To change polarity of a value, place the cursor on “+” or “-” and press either of the
RANGE keys. To change range for the value, place the cursor on the range symbol and
scroll using the range keys (P = pico, N = nano, µ = micro, m = milli, ^ = x1, K = kilo,
M = mega, G = giga, T = tera). A menu item or value is selected by pressing ENTER.
Digital output bit patterns — An output pattern is set by selecting a decimal value (0 to
15) that corresponds to the 4-bit BCD pattern of the output. To determine the output pattern value, add up the decimal weight values for the desired HI lines:
Output HI Line:

Out 4

Out 3

Out 2

Out 1

Decimal Weight:

For example, to set an output pattern to 0101 (lines 3 and 1 HI), set the output value to
5 (4 +1).

Limits configuration menu
The configuration menu for limits is structured as follows. Bullets denote the main items
of the menu. To access the menu, press CONFIG and then LIMIT.
LIMIT 1 — Configure Limit 1 test:
•
•
•

CONTROL — Enable or disable Limit 1 test.
HILIM — Set the HI limit (-9.999999T to +9.999999T).
LOLIM — Set the LO limit (-9.999999T to +9.999999T).

LIMIT 2 — Configure Limit 2 test:
•
•
•

CONTROL — Enable or disable Limit 2 test.
HILIM — Set the HI limit (-9.999999T to +9.999999T).
LOLIM — Set the LO limit (-9.999999T to +9.999999T).

PASS — Set the digital output bit pattern for the “all tests pass” condition (0 to 15).
DIG CLR (Digital Clear):
•
•
•

AUTO CLR — Enable or disable auto-clear for the digital output.
DEL (Delay) — Set the pass/fail pattern pulse width (0 to 60 sec with 10µsec
resolution).
DIGOUT — Set the digital output clear pattern (0 to 15).

Model 6487 Reference Manual

Limit Tests and Digital I/O

8-17

LIN4MOD (Line 4 Mode):
•
•

ENDOFTST (End of Test) — With this mode, Model 6487 will pulse the EOT line
when the test is finished. Use with catagory register component handlers.
/BUSY and BUSY — Pulls line 4 LO (/Busy) or HI (Busy) while the test is in process. Use with catagory pulse component handlers.

Arm layer configuration menu
To access the menu, press CONFIG and then TRIG. Use the RANGE keys to scroll to the
ARM menu.
•

klqb

ARM-IN — Select the “start of test” option:
– IMM (Immediate) — Test starts when LIMIT key is pressed.
– /STEST — Test starts when the handler pulls the SOT line of the Digital I/O
low.
– STEST — Test starts when the handler pulls the SOT line of the Digital I/O
high.
– BSTEST — Test starts when the handler pulls the SOT line of the Digital I/O
either high or low.
The other arm-in control sources are seldom used with component handlers, but
are available.

Performing limit tests
Step 1. Configure test system
As previously explained, testing the system could be as simple as connecting a DUT to the
Model 6487.

Step 2. Configure measurement
Configure the Model 6487 for the desired measurement as covered in the previous sections
of this manual.

Step 3. Configure limit tests
Configure the Model 6487 for the limit tests as explained in “Limit test configuration,”
page 8-16.

Step 4. Start testing process
To enable the limit tests, press the LIMIT key—the testing process will start when LIMIT
is pressed. The testing process can be terminated at any time by again pressing the LIMIT
key.

8-18

Limit Tests and Digital I/O

Model 6487 Reference Manual

SCPI programming — limit tests
Table 8-3
Limit test commands
Command
:CALCulate2
:FEED
:LIMit[1]
:UPPer
[:DATA]
:SOURce2 or
:LOWer
[:DATA]
:SOURce2 or
:STATe
:FAIL?
:LIMit2
:UPPer
[:DATA]
:SOURce2 or
:LOWer
[:DATA]
:SOURce2 or
:STATe
:FAIL?
:CLIMits
:CLEar
[:IMMediate]
:AUTO
:PASS
:SOURce2 or
:DATA?
:LATest?

Description
CALCulate2 Subsystem:
Select input path for limit testing: CALCulate[1]
or SENSe[1].
Limit 1 Testing:
Configure upper limit:
Set limit: -9.99999e20 to 9.99999e20.
Specify 4-bit output “fail” pattern.
Configure lower limit:
Set limit: -9.99999e20 to 9.99999e20.
Specify 4-bit output “fail” pattern.
Enable or disable Limit 1 test.
Return result of Limit 1 test: 0 (pass) or 1 (fail).
Limit 2 Testing:
Configure upper limit:
Set limit: -9.99999e20 to 9.99999e20.
Specify 4-bit output “fail” pattern.
Configure lower limit:
Set limit: -9.99999e20 to 9.99999e20.
Specify 4-bit output “fail” pattern.
Enable or disable Limit 2 test.
Return result of Limit 2 test: 0 (pass) or 1 (fail).
Composite Limits:
Clear I/O port and restore it back to
SOURce2:TTL settings:
Clears I/O port immediately.
When enabled, I/O port clears when :INITiate
sent.
Define “pass” digital output pattern.
Specify 4-bit pass pattern (no failures).
Return CALC2 reading(s) triggered by INITiate.
Return last (latest) CALC2 reading.

Default

Ref

SENS

1.0
15

-1.0
15
OFF

B
C

1.0
15
-1.0
15
OFF

B
C

B
D
D

Model 6487 Reference Manual

Limit Tests and Digital I/O

8-19

Table 8-3 (cont.)
Limit test commands
Command
:SOURce2
:TTL or
:CLEar
[:IMMediate]
:AUTO
:DELay
:TTL4
:MODE
:BSTate

Description
SOURce2 Subsystem:
Specify 4-bit digital output clear pattern.
Clear I/O port (return output to TTL pattern):
Clear I/O port immediately.
Enable or disable auto-clear.
Specify delay (pulse-width) for pass/fail
pattern: 0 to 60 (sec).
Line 4 Mode configuration:
Select output line 4 mode: EOTest or BUSY.
Select active TTL level for busy: 1 (HI) or 0 (LO).
Trigger Subystem:
Arm Layer:
Select control source: NSTest, PSTest, BSTest, or
IMMediate.
Initiate one trigger cycle.
FORMat subsystem:
Select data format for reading output patterns:
= ASCii
Decimal format
HEXadecimal
Hexadecimal format
OCTal
Octal format
BINary
Binary format

ARM
:SOURce
INITiate
FORMat
:SOURce2

Default Ref
15

OFF
0.0001

EOT
0
Sec 7
IMM

ASC

A) :FEED
Name parameters:
•
•

CALCulate1 — Limit tests will be performed on the result of a math calculation
(mX+b, m/x+b, or log).
SENSe — Limit tests will be performed on the input signal. Note however, that Rel
can be used on the result of a math calculation as well as the input signal. Limit
tests will be performed on the result of the Rel operation (see CALCulate1:NULL).
Details on relative, mX+b, m/X+b, and log are provided in Section 5.

8-20

Limit Tests and Digital I/O

Model 6487 Reference Manual

B) and parameters
= #Bxxxx
= #Hx
= #Qxx

Binary format (each x = 1 or 0)
Hexadecimal format (x = 0 to F)
Octal format (x = 0 to 17)

= 0 to 15

Decimal format

An output pattern is set by sending a parameter value that corresponds to the 4-bit BCD
pattern of the output. The parameter value can be sent in the binary, decimal, hexadecimal,
or octal format. For example, if you wish to set lines 4, 2, and 1 HI, the binary parameter
value would be 1011. To use one of the other formats, convert the binary number to its
decimal, hexadecimal, or octal equivalent:
Binary 1011 = Decimal 11 = Hexadecimal B = Octal 13
The (non-decimal numeric) parameter type is used to send non-decimal values.
These values require a header (#B, #H, or #Q) to identify the data format being sent. The
letter in the header can be upper or lower case. The (numeric representation format) parameter type is used to send decimal values and does not use a header.
The following examples show the proper parameter syntax to set an output pattern to 1101
(lines 4, 3, and 1 set HI):
#b1101
#hD
#q15
13
klqb

Binary format ( parameter type)
Hexadecimal format ( parameter type)
Octal format ( parameter type)
Decimal format ( parameter type)
When a query command to read a programmed output pattern (i.e.,
CALC2:LIM:UPP:SOUR2?) is sent, the format for the returned value is determined by the presently selected response message format for output patterns
(see FORMat:SOURce2 command in Table 8-3).

C) :FAIL?
In the event of a failure, you can read the measurement event register to determine which
limit (upper or lower) failed. See Section 10 to program and read the measurement event
register.

D) :DATA? and :DATA:LATest?
The INITiate command must be sent to perform the programmed number of measurements. If the instrument is programmed to perform a finite number of measurements, the
:DATA? command will return all the CALC2 readings after the last reading is taken. The
:DATA:LATest? command will only return the last (latest) CALC2 reading.

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8-21

If the instrument is programmed to perform an infinite number of measurements (arm
count or trigger count set to infinite), you cannot use the :DATA? command to return
CALC2 readings. However, you can use the :DATA:LATest? command to return the last
CALC2 reading after aborting the measurement process. After sending the INITiate command to start the measurement process, use the ABORt command to abort the measurement process, then use :DATA:LATest? to return the last CALC2 reading.
Sending :DATA? or :DATA:LATest? without first sending INITiate will return “old” readings or cause an error (-220) if limit is not enabled or there are no readings available.

:ARM:SOURce

Typical “start of test” options:
•
•
•
•

IMMediate — Test starts when LIMIT key is pressed.
NSTest — Test starts when component handler pulls the SOT line low.
PSTest — Test starts when component handler pulls the SOT line high.
BSTest — Test starts when component handler pulls the SOT line high or low.

Programming example
The following command sequence will test DUT using the limit tests example shown in
Figure 8-2.
*RST
CALC2:LIM:UPP 2e-3
CALC2:LIM:LOW -2e-3
CALC2:LIM:STAT ON
CALC2:LIM2:UPP 1e-3
CALC2:LIM2:LOW -1e-3
CALC2:LIM2:STAT ON
SYST:ZCH OFF
INIT
CALC2:LIM:FAIL?
CALC2:LIM2:FAIL?

'
'
'
'
'
'
'
'
'
'
'
'

Restore RST defaults.
Set upper limit for Limit 1 (2mA).
Set lower limit for Limit 1 (-2mA).
Enable Limit 1 test.
Set upper limit for Limit 2 (1mA).
Set lower limit for Limit 2 (-1mA).
Enable Limit 2 test.
Connect DUT to input.
Disable zero check.
Perform tests on DUT (one measurement).
Return result of Limit 1 test.
Return result of Limit 2 test.

Remote Operation
•

Selecting and configuring an interface — Explains how to select and configure
an interface: GPIB or RS-232.

•

GPIB operation and reference — Covers the following GPIB topics:
GPIB bus standards
GPIB bus connections
Primary address
General IEEE-488 bus commands
Front panel GPIB operation
Programming syntax

•

RS-232 interface reference — Provides basic reference information for the
RS-232 interface and explains how to make connections to the computer.

9-2

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Model 6487 Reference Manual

Selecting and configuring an interface
Interfaces
The Model 6487 supports two built-in remote interfaces:
•
•

GPIB interface
RS-232 interface

You can use only one interface at a time. At the factory, the GPIB bus is selected. You can
select the interface only from the front panel. The interface selection is stored in nonvolatile memory; it does not change when power has been off or after a remote interface
reset.
GPIB interface — The GPIB is the IEEE-488 interface. The Model 6487 must be
assigned to a unique address. At the factory the address is set to 22, but can be set to any
value from 0 to 30. However, the address must not conflict with the address assigned to
other instruments in the system. You can use either the SCPI or DDC language to program
the instrument.
RS-232 interface — When using the RS-232 interface, you must set baud rate, data bits,
parity, terminator, and flow control. For the RS-232 interface, you can only use the SCPI
language to program the instrument.

Languages
For the GPIB interface, there are three programming languages to choose from:
•
•
•
klqb

SCPI language (488.2)
DDC language
488.1 language
For the RS-232 interface, only the SCPI language can be used to program the
instrument. When the RS-232 interface is selected, it automatically defaults to
SCPI.

SCPI language — Standard Commands for Programmable Instrument (SCPI) is fully
supported by the GPIB and RS-232 interfaces. Always calibrate the Model 6487 using the
SCPI language.
DDC language — The Model 6487 implements most DDCs (device-dependent commands) available in the Keithley Model 487 picoammeter. The available commands are
provided in Appendix C. See the Model 487 Instruction Manual for details on operation.
The PDF of this manual is on the CD-ROM that was included with your shipment.
488.1 language — See Appendix E for details.

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9-3

Interface selection and configuration procedures
klqb

The unit will reset if the language is changed (SCPI, 488.1, and DDC).

When you select (enable) the GPIB interface, the RS-232 interface disables. Conversely,
selecting (enabling) the RS-232 interface disables the GPIB interface.
Select the interface from the COMM menu structure (access by pressing the COMM key
while in local). Use the RANGE keys to change the selected interface (RS-232 or GPIB).
Press ENTER to save the change.
klqb

When an interface is enabled (on) or disabled (off), the instrument will exit from
the menu structure and perform the power-on sequence.

Configuring the GPIB interface
Select the GPIB interface from the COMM menu structure (access by pressing the
COMM key while in local). After selecting the GPIB interface, press the CONFIG key and
then the COMM key to configure the GPIB address and language. From this menu you can
check or change the following settings:
•
•

Primary address: 0–30
Language: SCPI (SCPI 1996.0 which includes 488.2), 488.1, or DDC

Press the RANGE keys to scroll through ADDress and LANGuage available. To make
changes to a setting, press the cursor right key. Then use the RANGE keys and the cursor
keys to select and modify the value as desired. Press ENTER to save the changes and stay
in the menu (pressing EXIT also saves the changes but leaves the menu).

RS-232 interface
klqb

Only the SCPI language can be used with the RS-232 interface. The instrument
defaults to the SCPI language when the RS-232 interface is selected (enabled).

Select the RS-232 interface from the COMM menu structure (access by pressing the
COMM key while in local). After selecting the RS-232 interface, press the CONFIG key
and then the COMM key to configure the RS-232 interface and check or change the following settings:
•
•
•
•
•
klqb

BAUD: Baud rate (57.6K, 38.4k, 19.2k, 9600, 4800, 2400, 1200, 600, or 300)
BITS: Data bits (7 or 8)
PARITY: Parity (NONE, ODD, or EVEN)
TX TERMINATOR: Terminator (CR, LF, CRLF, or LFCR)
FLOW: Flow control (NONE or Xon/Xoff)
See “RS-232 interface reference,” on page 9-16 for information on RS-232
settings and connections to the computer.

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Model 6487 Reference Manual

Press the RANGE keys to scroll through the available RS-232 settings. To make changes
to a setting, press the right cursor key and then use the RANGE keys to select and modify
the value as desired. Press ENTER to save the changes and move to the next menu item
(pressing EXIT also saves the changes but leaves the menu). At the last menu item,
ENTER will save and exit the menu.

GPIB operation and reference
GPIB bus standards
The GPIB bus is the IEEE-488 instrumentation data bus with hardware and programming
standards originally adopted by the IEEE (Institute of Electrical and Electronic Engineers)
in 1975. The Model 6487 conforms to these standards:
•
•

IEEE-488.1-1987
IEEE-488.2-1992

These standards define a syntax for sending data to and from instruments, how an instrument interprets this data, what registers should exist to record the state of the instrument,
and a group of common commands.
•

SCPI 1996.0 (Standard Commands for Programmable Instruments)

This standard defines a command language protocol. It goes one step further than
IEEE-488.2-1992 and defines a standard set of commands to control every programmable
aspect of an instrument.

GPIB bus connections
To connect the Model 6487 to the GPIB bus, use a cable equipped with standard IEEE-488
connectors as shown in Figure 9-1.
Figure 9-1
IEEE-488 connector

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Remote Operation

9-5

To allow many parallel connections to one instrument, stack the connector. Two screws are
located on each connector to ensure that connections remain secure. Current standards call
for metric threads, which are identified with dark-colored screws. Earlier versions had different screws, which were silver-colored. Do not use these types of connectors on the
Model 6487, because it is designed for metric threads.
Figure 9-2 shows a typical connecting scheme for a multi-unit test system.
Figure 9-2
Multi-unit connections
Instrument

Instrument

Controller

To avoid possible mechanical damage, stack no more than three connectors on any one
unit.
klqb

To minimize interference caused by electromagnetic radiation, use only shielded
IEEE-488 cables. Available shielded cables from Keithley are Models 7007-1
and 7007-2.

Remote Operation

Model 6487 Reference Manual

To connect the Model 6487 to the IEEE-488 bus, follow these steps:
1.

Line up the cable connector with the connector located on the rear panel. The connector is designed so that it will fit only one way. Figure 9-3 shows the location of
the IEEE-488 connector.

Figure 9-3
IEEE-488 and RS-232 connector locations
RS-232

IEEE-488

MADE IN
U.S.A.

CAT I

IEEE-488

ANALOG OUT

(CHANGE IEEE ADDRESS
WITH FRONT PANEL MENU)

DIGITAL I/O

!
505V PK
505V PK

505V PK

TRIGGER LINK

INPUT

RS-232

V-SOURCE OUTPUT
505V PK TO CHASSIS
LO

HI INTERLOCK
FUSE

505V
MAX

2.
3.
4.

klqb

120

9-6

LINE

400mAT
(SB)

100 VAC
120 VAC

200mAT
(SB)

220 VAC
240 VAC

LINE RATING
50, 60Hz
50 VA MAX

Tighten the screws securely, making sure not to over tighten them.
Connect any additional connectors from other instruments as required for your
application.
Make sure that the other end of the cable is properly connected to the controller.
Most controllers are equipped with an IEEE-488 style connector, but a few may
require a different type of connecting cable. See your controllers instruction manual for information about properly connecting to the IEEE-488 bus.
You can only have 15 devices connected to an IEEE-488 bus, including the controller. The maximum cable length is either 20 meters or two meters times the
number of devices, whichever is less. Not observing these limits may cause
erratic bus operation.

Primary address
The Model 6487 ships from the factory with a GPIB address of 22. When the instrument
powers up, it momentarily displays the primary address. You can set the address to a value
of 0-30. Do not assign the same address to another device or to a controller that is on the
same GPIB bus.

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9-7

Usually controller addresses are 0 or 21, but see the controllers instruction manual for
details. Make sure the address of the controller is the same as that specified in the controllers programming language. To make sure the unit’s interface is properly selected and configured or to check or change the GPIB address, refer to “Selecting and configuring an
interface,” page 9-2.

General IEEE-488 bus commands
Commands and associated statements
General commands are those commands, such as DCL, that have the same general meaning regardless of the instrument. Table 9-1 lists the general bus commands.
Table 9-1
General bus commands
Command

Effect on Model 6487

REN

Goes into remote when next addressed to listen.

IFC

Reset interface; all devices go into talker and listener idle states.

LLO

LOCAL key locked out.

GTL

Cancel remote; restore front panel operation for Model 6487.

DCL

Returns all devices to known conditions.

SDC

Returns Model 6487 to known conditions.

GET

Initiates a trigger.

SPE, SPD

Serial polls Model 6487.

REN (remote enable)
The remote enable command is sent to the Model 6487 by the controller to set up the
instrument for remote operation. Generally, the instrument should be placed in the remote
mode before you attempt to program it over the bus. Simply setting REN true does not
actually place the instrument in the remote state. You must address the instrument to listen
after setting REN true before it goes into remote.
Note that the instrument does not have to be in remote to be a talker.
Note that all front panel controls, except for LOCAL and POWER, are inoperative while
the instrument is in remote. You can restore normal front panel operation by pressing the
LOCAL key.

9-8

Remote Operation

Model 6487 Reference Manual

IFC (interface clear)
The IFC command is sent by the controller to place all instruments on the bus in the local,
talker, listener idle states. The Model 6487 responds to the IFC command by canceling
front panel TALK or LSTN lights, if the instrument was previously placed in one of those
states. Note that this command does not affect the status of the instrument; settings, data,
and event registers are not changed.
To send the IFC command, the controller must set the IFC line true for a minimum of
100µs.

LLO (local lockout)
Use the LLO command to prevent local operation of the instrument. After the unit receives
LLO, all its front panel controls except the POWER are inoperative. In this state, pressing
LOCAL will not restore control to the front panel. The GTL command restores control to
the front panel.

GTL (go to local)
Use the GTL command to put a remote mode instrument into local mode. The GTL command also restores front panel key operation.

DCL (device clear)
Use the DCL command to clear the GPIB interface and return it to a known state. Note
that the DCL command is not an addressed command, so all instruments equipped to
implement DCL will do so simultaneously.
When the Model 6487 receives a DCL command, it clears the input buffer and output
queue, cancels deferred commands, and clears any command that prevents the processing
of any other device command. A DCL does not affect instrument settings and stored data.

SDC (selective device clear)
The SDC command is an addressed command that performs essentially the same function
as the DCL command. However, since each device must be individually addressed, the
SDC command provides a method to clear only selected instruments instead of clearing all
instruments simultaneously, as is the case with DCL.

GET (group execute trigger)
GET is a GPIB trigger that is used as an event to control operation. The Model 6487 reacts
to this trigger if it is the programmed control source. The control source is programmed
from the SCPI TRIGger subsystem.

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9-9

SPE, SPD (serial polling)
Use the serial polling sequence to obtain the Model 6487 serial poll byte. The serial poll
byte contains important information about internal functions. Generally, the serial polling
sequence is used by the controller to determine which of several instruments has requested
service with the SRQ line. However, the serial polling sequence may be performed at any
time to obtain the status byte from the Model 6487.

Front panel GPIB operation
The following paragraphs describe aspects of the front panel that are part of GPIB operation, including messages, status indicators, and the LOCAL key.

Error and status messages
See Appendix B for a list of error and status messages associated with IEEE-488 programming. The instrument can be programmed to generate an SRQ and command queries can
be performed to check for specific error conditions.

GPIB status indicators
The REM (remote), TALK (talk), LSTN (listen), and SRQ (service request) annunciators
show the GPIB bus status. Each of these indicators is described below.
•

•

REM — This indicator shows when the instrument is in the remote state. REM
does not necessarily indicate the state of the REM line, as the instrument must be
addressed to listen with REM true before the REM indicator turns on. When the
instrument is in remote, all front panel keys, except for the LOCAL key, are locked
out. When REM is turned off, the instrument is in the local state and front panel
operation is restored.
TALK — This indicator is on when the instrument is in the talker active state.
Place the unit in the talk state by addressing it to talk with the correct MTA (My
Talk Address) command. TALK is off when the unit is in the talker idle state. Place
the unit in the talker idle state by sending a UNT (Untalk) command, addressing it
to listen, or sending the IFC (Interface Clear) command.
LSTN — This indicator is on when the Model 6487 is in the listener active state,
which is activated by addressing the instrument to listen with the correct MLA (My
Listen Address) command. LSTN is off when the unit is in the listener idle state.
Place the unit in the listener idle state by sending UNL (Unlisten), addressing it to
talk, or sending the IFC (Interface Clear) command over the bus.
SRQ — You can program the instrument to generate a service request (SRQ) when
one or more errors or conditions occur. When this indicator is on, a service request
has been generated. This indicator stays on until the serial poll byte is read or all
the conditions that caused SRQ have ceased to exist.

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Model 6487 Reference Manual

LOCAL key
The LOCAL key cancels the remote state and restores local operation of the instrument.
Pressing the LOCAL key also turns off the REM indicator and returns the display to normal if a user-defined message was displayed. If the unit is in local (not in remote), the
LOCAL key acts as a configure key (see “Front panel operation,” page 4-8.)
If the LLO (Local Lockout) command is in effect, the LOCAL key is also inoperative.

Programming syntax
The following paragraphs cover syntax for both common commands and SCPI commands.
For more information, see the IEEE-488.2 and SCPI standards.

Command words
Program messages are made up of one or more command words.
Commands and command parameters
Common commands and SCPI commands may or may not use a parameter. The following
are some examples:
*SAV
*RST
:DISPlay:ENABle
:SYSTem:PRESet

Parameter (NRf) required.
No parameter used.
Parameter required.
No parameter used.

Put at least one space between the command word and the parameter.
•

Brackets [ ] — Some command words are enclosed in brackets ([ ]). These brackets are used to denote an optional command word that does not need to be included
in the program message. For example:
:INITiate[:IMMediate]
These brackets indicate that :IMMediate is implied (optional) and does not have to
be used. Thus, the above command can be sent in one of two ways:
:INITiate or :INITiate:IMMediate
Notice that the optional command is used without the brackets. When using
optional command words in your program, do not include the brackets.

•

Parameter types — The following are some of the common parameter types:

Boolean — Used to enable or disable an instrument operation. 0 or
OFF disables the operation and 1 or ON enables the operation.
:DISPlay:ENABle ON

Enable the display

Model 6487 Reference Manual

Remote Operation

Name parameter — Select a parameter name from a listed group.

= NEVer
= NEXT

:CALCulate:FORMat MXB

Set bits B0 and B4 of Service
Request Enable Register

Numeric value — Can consist of an NRf number or one of the following name parameters: DEFault, MINimum, or MAXimum.
When the DEFault parameter is used, the instrument is programmed
to the *RST default value. When the MINimum parameter is used,
the instrument is programmed to the lowest allowable value. When
the MAXimum parameter is used, the instrument is programmed to
the largest allowable value.
:ARM:TIMer 0.1
:ARM:TIMer DEFault
:ARM:TIMer MINimum
:ARM:TIMer MAXimum

•

Set buffer size to 20

Non-decimal numeric — A non-decimal value that can be used to
program status enable registers. A unique header identifies the format; #B (binary), #H (hexadecimal), and #Q (octal).
*SRE #B10001

Select Mx + B calculation

Numeric representation format — A number that can be expressed
as an integer (e.g., 8), a real number (e.g., 23.6), or an exponent
(2.3E6).
:TRACe:POINts 20

9-11

Sets timer to 100 msec.
Sets timer to 0.1 sec.
Sets timer to 1 msec.
Sets timer to 999999.999 sec.

Angle brackets < > — Used to denote a parameter type. Do not include the brackets in the program message.
:DISPlay:ENABle
The indicates that a Boolean type parameter is required. Thus, to enable the
display, you must send the command with the ON or 1 parameter as follows.
:DISPlay:ENABle ON or 1

9-12

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Model 6487 Reference Manual

Query commands
The query command requests the presently programmed status. It is identified by the question mark (?) at the end of the fundamental form of the command. Most commands have a
query form.
:ARM:TIMer?

Queries the timer interval

Most commands that require a numeric parameter () can also use the DEFault, MINimum, and MAXimum parameters for the query form. These query forms are used to determine the *RST default value and the upper and lower limits for the fundamental
command.
:ARM:TIMer? DEFault
:ARM:TIMer? MINimum
:ARM:TIMer? MAXimum

Queries the *RST default value
Queries the lowest allowable value
Queries the largest allowable value

Case sensitivity
Common commands and SCPI commands are not case sensitive. You can use upper or
lower case and any case combination. Examples:
*RST
:DATA?
:SYSTem:PRESet

= *rst
= :data?
= :system:preset

Long-form and short-form versions
A SCPI command word can be sent in its long-form or short-form version. The command
tables in this manual use the long-form version. However, the short-form version is indicated by upper case characters.
:SYSTem:PRESet
:SYST:PRES
:SYSTem:PRES

long-form
short form
long-form and short-form combination

Note that each command word must be in either long-form or short-form. For example,
:SYSTe:PRESe is illegal and will generate an error. The command will not be executed.

Short-form rules
Use the following rules to determine the short-form version of any SCPI command:
•

If the length of the command word is four letters or less, no short form version
exists.
:auto = :auto

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9-13

These rules apply to command words that exceed four letters:
•

If the fourth letter of the command word is a vowel, delete it and all letters after it.
immediate = :imm

•

If the fourth letter of the command word is a consonant, retain it but drop all the
letters after it.
:format = :form

•

If the command contains a question mark (?) or a non-optional number included in
the command word, you must include it in the short-form version.
:delay? = :del?

•

Command words or characters that are enclosed in brackets ([ ]) are optional and need
not be included in the program message.

Program messages
A program message is made up of one or more command words sent by the computer to
the instrument. Each common command is simply a three letter acronym preceded by an
asterisk (*). The following SCPI commands from the STATus subsystem are used to help
explain how command words are structured to formulate program messages.
Command structure
:STATus
:OPERation

Path (Root)
Path

:ENABle

Command and parameter

:ENABle?

Query command

:PRESet

Command

Single command messages
The above command structure has three levels. The first level is made up of the root command (:STATus) and serves as a path. The second level is made up of another path
(:OPERation) and a command (:PRESet). The third path is made up of one command for
the :OPERation path. The three commands in this structure can be executed by sending
three separate program messages as follows:
:stat:oper:enab
:stat:oper:enab?
:stat:pres
In each of the above program messages, the path pointer starts at the root command (:stat)
and moves down the command levels until the command is executed.

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Model 6487 Reference Manual

Multiple command messages
You can send multiple command messages in the same program message as long as they
are separated by semicolons (;). The following is an example showing two commands in
one program message:
:stat:oper; :stat:oper:enab
When the above is sent, the first command word is recognized as the root command (:stat).
When the next colon is detected, the path pointer moves down to the next command level
and executes the command. When the path pointer sees the colon after the semicolon (;), it
resets back to the root level and starts over.
Commands that are on the same command level can be executed without having to retype
the entire command path. Example:
:stat:oper:enab ; enab?
After the first command (:enab) is executed, the path pointer is at the third command level
in the structure. Since :enab? is also on the third level, it can be entered without repeating
the entire path name. Notice that the leading colon for :enab? is not included in the program message. If a colon were included, the path pointer would reset to the root level and
expect a root command. Since :enab? is not a root command, an error would occur.

Command path rules
•

•

Each new program message must begin with the root command, unless it is
optional (e.g., [:SENSe]). If the root is optional, simply treat a command word on
the next level as the root.
The colon (:) at the beginning of a program message is optional and need not be
used.
:stat:pres = stat:pres

•

•
•

When the path pointer detects a colon (:), it moves down to the next command
level. An exception is when the path pointer detects a semicolon (;), which is used
to separate commands within the program message.
When the path pointer detects a colon (:) that immediately follows a semicolon (;),
it resets to the root level.
The path pointer can only move down. It cannot be moved up a level. Executing a
command at a higher level requires that you start over at the root command.

Using common commands and SCPI commands in the same message
Both common commands and SCPI commands can be used in the same message as long
as they are separated by semicolons (;). A common command can be executed at any command level and will not affect the path pointer.
:stat:oper:enab ; *ESE

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9-15

Program Message Terminator (PMT)
Each program message must be terminated with an LF (line feed), EOI (end or identify),
or an LF+EOI. The bus will hang if your computer does not provide this termination. The
following example shows how a program message must be terminated:
:trac:poin 10

Command execution rules
•
•
•
•
•

Commands execute in the order that they are presented in the program message.
An invalid command generates an error and, of course, is not executed.
Valid commands that precede an invalid command in a multiple command program
message are executed.
Valid commands that follow an invalid command in a multiple command program
message are ignored.
For fastest command execution:
1. Do not use optional command words (i.e., [:SENSE [1]]).
2. Do not use the colon (:) at the beginning of a program message.
3. Always use the short-form versions of commands and parameters.
4. Minimize the amount of “white” space in command strings.
5. Keep numeric parameters simple (i.e., 1 vs. 1.000e + 00).
6. Use all uppercase.

Response messages
A response message is the message sent by the instrument to the computer in response to a
query command program message.

Sending a response message
After sending a query command, the response message is placed in the output queue.
When the Model 6487 is addressed to talk, the response message is sent from the output
queue to the computer.

Multiple response messages
If you send more than one query command in the same program message (see “Multiple
command messages,” on page 9-14), the multiple response messages for all the queries is
sent to the computer when the Model 6487 is addressed to talk. The responses are sent in
the order that the query commands were sent and are separated by semicolons (;). Items
within the same query are separated by commas (,). The following example shows the
response message for a program message that contains four single item query commands:
0; 1; 1; 0

9-16

Remote Operation

Model 6487 Reference Manual

Response Message Terminator (RMT)
Each response is terminated with an LF (line feed) and EOI (end or identify). The following example shows how a multiple response message is terminated:
0; 1; 1; 0;

Message exchange protocol
Two rules summarize the message exchange protocol:
Rule 1.

Always tell the Model 6487 what to send to the computer. The following two
steps must always be performed to send information from the instrument to the
computer:
1. Send the appropriate query command(s) in a program message.
2. Address the Model 6487 to talk.

Rule 2.

The complete response message must be received by the computer before
another program message can be sent to the Model 6487.

RS-232 interface reference
Sending and receiving data
The RS-232 interface transfers data using seven or eight data bits and one stop bit. Parity
selections include none, odd, or even. When using the RS-232 interface, the unit will not
respond to DDC or general GPIB commands.

RS-232 settings
The procedure to select and configure the RS-232 interface is provided in “Selecting and
configuring an interface,” page 9-2. Make sure the controller you connect to the
Model 6487 also uses these settings.
klqb

You can break data transmissions by sending a ^C or ^X character string to the
Model 6487. This clears any pending operation and discards any pending
output.

Baud rate
The baud rate is the rate at which the Model 6487 and the programming terminal communicate. You can choose from one of the following rates: 57.6k, 38.4k, 19.2k, 9600, 4800,
2400, 1200, 600, or 300.

Model 6487 Reference Manual

Remote Operation

9-17

Make sure that the programming terminal that you are connecting to the Model 6487 can
support the baud rate you selected. Both the Model 6487 and the other device must be configured for the same baud rate.

Data and stop bits
The RS-232 can be set to transfer data using seven or eight data bits and one stop bit.

Parity
Parity for the RS-232 interface can be set to none, even, or odd.

Terminator
The Model 6487 can be configured to terminate each program message that it transmits to
the controller with any of the following combinations of and :
•
•
•
•

LF
CR
LFCR
CRLF

line feed
carriage return
line feed, carriage return
carriage return, line feed

Flow control (signal handshaking)
Signal handshaking between the controller and the instrument allows the two devices to
communicate to each other regarding being ready or not ready to receive data. The
Model 6487 does not support hardware handshaking (flow control).
Software flow control is in the form of X_ON and X_OFF characters and is enabled when
XonXoFF is selected from the RS232 FLOW menu. When the input queue of the
Model 6487 becomes more than i full, the instrument issues an X_OFF command. The
control program should respond to this and stop sending characters until the Model 6487
issues the X_ON, which it will do once its input buffer has dropped below full. The
Model 6487 recognizes X_ON and X_OFF sent from the controller. An X_OFF will cause
the Model 6487 to stop outputting characters until it sees an X_ON. Incoming commands
are processed after the character is received from the controller.
If NONE is the selected flow control, then there will be no signal handshaking between the
controller and the Model 6487. Data will be lost if transmitted before the receiving device
is ready.

9-18

Remote Operation

Model 6487 Reference Manual

RS-232 connections
The RS-232 serial port can be connected to the serial port of a controller (i.e., personal
computer) using a straight through RS-232 cable terminated with DB-9 connectors. Do
not use a null modem cable. The serial port uses the transmit (TXD), receive (RXD), and
signal ground (GND) lines of the RS-232 standard. It does not use the hardware handshaking lines CTS and RTS. Figure 9-4 shows the rear panel connector for the RS-232 interface and Table 9-2 shows the pinout for the connector. The connector location on the rear
panel is shown in Figure 9-3.
Figure 9-4
RS-232 interface connector
5 4 3 2 1

9 8 7 6
RS232
Rear Panel Connector

If your computer uses a DB-25 connector for the RS-232 interface, you will need a cable
or adapter with a DB-25 connector on one end and a DB-9 connector on the other, wired
straight through (not null modem). Table 9-3 provides pinout identification for the 9-pin
(DB-9) or 25-pin (DB-25) serial port connector on the computer (PC).
Table 9-2
RS-232 connector pinout
Pin number

Description

DCD, data carrier detect

TXD, transmit data

RXD, receive data

DTR, data terminal ready

GND, signal ground

DSR, data set ready

RTS, request to send

CTS, clear to send

No connections

RTS and CTS are tied together.
DCD, DTR, and DSR are tied together.
TXD and RXD are swapped on Model 6487 and PC so
that null modem cable is not required.

Model 6487 Reference Manual

Remote Operation

Table 9-3
PC serial port pinout
DB-9
pin number

DB-25
pin number

DCD, data carrier detect

RXD, receive data

TXD, transmit data

DTR, data terminal ready

GND, signal ground

DSR, data set ready

RTS, request to send

CTS, clear to send

RI, ring indicator

Signal

Error messages
See Appendix B for RS-232 error messages.

9-19

Status Structure
•

Overview — Provides an operational overview of the status structure for the
Model 6487.

•

Clearing registers and queues — Covers the actions that clear (reset) registers and
queues.

•

Programming and reading registers — Explains how to program enable registers
and read any register in the status structure.

•

Status byte and service request (SRQ) — Explains how to program the status
byte to generate service requests (SRQs). Shows how to use the serial poll
sequence to detect SRQs.

•

Status register sets — Provides bit identification and command information for
the four status register sets: standard event status, operation event status, measurement event status, and questionable event status.

•

Queues — Provides details and command information on the output queue and
error queue.

10-2

Status Structure

Model 6487 Reference Manual

Overview
The Model 6487 provides a series of status registers and queues allowing the operator to
monitor and manipulate the various instrument events. The status structure is shown in
Figure 10-1. The heart of the status structure is the status byte register. This register can be
read by the user’s test program to determine if a service request (SRQ) has occurred and
what event caused it.
Status byte and SRQ — The status byte register receives the summary bits of four status
register sets and two queues. The register sets and queues monitor the various instrument
events. When an enabled event occurs, it sets a summary bit in the status byte register.
When a summary bit of the status byte is set and its corresponding enable bit is set (as programmed by the user), the RQS/MSS bit will set to indicate that an SRQ has occurred.
Status register sets — A typical status register set is made up of a condition register, an
event register, and an event enable register. A condition register is a read-only register that
constantly updates to reflect the present operating conditions of the instrument.
When an event occurs, the appropriate event register bit sets to 1. The bit remains latched
to 1 until the register is reset. When an event register bit is set and its corresponding enable
bit is set (as programmed by the user), the output (summary) of the register will set to 1,
which in turn sets the summary bit of the status byte register.
Queues — The Model 6487 uses an output queue and an error queue. The response messages to query commands are placed in the output queue. As various programming errors
and status messages occur, they are placed in the error queue. When a queue contains data,
it sets the appropriate summary bit of the status byte register.

Model 6487 Reference Manual

Status Structure

Figure 10-1
Model 6487 status mode structure
Questionable Event Registers
Condition
Register

Event Enable
Register

Event
Register

0
1
2
3
4
5
6
Calibration Summary Cal
8
9
10
11
12
13
Command Warning Warn
(Always Zero) 15
:CONDition?

0
1
2
3

4
5
6
Cal
8
9
10
11
12
13
Warn
15

0
1
2
3

&
&
&

4
5
6
Cal
8
9
10
11
12
13
Warn
15

&
&
&
&
&
&
&
&
&
&
&

[:EVENt]?

Logical
OR

Error Queue

:ENABle
:ENABle?

Output Queue
Service
Request
Enable
Register

Status
Byte
Register
MSB
1
EAV
QSB
MAV
ESB
RQS/MSS
OSB

Standard Event Registers
Event
Event Enable
Register
Register
Operation Complete
Query Error
Device Specific Error
Execution Error
Command Error
User Request
Power On

(Always Zero)

OPC
1
QYE
DDE
EXE
CME
URQ
PON
8
9
10
11
12
13
14
15
*ESR?

&
&
&
&
&
&
&
&
&
&
&
&
&
&
&
&

OPC
1
QYE
DDE
EXE
CME
URQ
PON
8
9
10
11
12
13
14
15
*ESE
*ESE?

0
Low Limit 1 Fail
LL1F
High Limit 1 Fail HL1F
Low Limit 2 Fail
LL2F
High Limit 2 Fail HL2F
Limits Pass
LP
Reading Available RAV
Reading Overflow ROF
Buffer Available
BAV
Buffer Full
BFL
Input Overvoltage IOV
Interlock Asserted INT
12
13
Voltage Source Compliance VSC
(Always Zero) 15
:CONDition?

Event
Register
0
LL1F
HL1F
LL2F
HL2F
LP
RAV
ROF
BAV
BFL
IOV
INT
12
13
VSC
15
[:EVENt]?

&
&
&
&
&
&
&
&
&
&
&
&
&
&

0
LL1F
HL1F
LL2F
HL2F
LP
RAV
ROF
BAV
BFL
IOV
INT
12
13
VSC
15

:ENABle
:ENABle?

&
&
&
&

Logical
OR

*SRE
*SRE?

Master Summary Status (MSS)

Note : RQS bit is in serial poll byte,
MSS bit is in *STB? response.
Operation Event Registers

Event Enable
Register
&

MSB = Measurement Summary Bit
EAV = Error Available
QSB = Questionable Summary Bit
MAV = Message Available
ESB = Event Summary Bit
RQS/MSS = Request for Service/Master Summary Status
OSB = Operation Summary Bit

Measurement Event Registers
Condition
Register

*STB?
Logical
OR

MSB
1
EAV
QSB
MAV
ESB
6
OSB

Condition
Register
Calibrating
A-V Ohms

Cal
A-V
2
Swp
4
Trig
Arm
7
8
9
Idle
11
12
13
14
15

:CONDition?

[:EVENt]?

Sweeping

Logical
OR

Event
Register

Trigger Layer
Arm Layer

Idle

Event Enable
Register
&
&
&
&
&
&
&
&
&
&
&
&
&
&
&
&

Cal
A-V
2
Swp
4
Trig
Arm
7
8
9
Idle
11
12
13
14
15

:ENABle
:ENABle?

Logical
OR

10-3

10-4

Status Structure

Model 6487 Reference Manual

Clearing registers and queues
When the Model 6487 is turned on, the bits of all registers in the status structure are clear
(reset to 0) and the two queues are empty. Commands to reset the event and event enable
registers and the error queue are listed in Table 10-1. In addition to these commands, any
enable register can be reset by sending the 0 parameter value with the individual command
to program the register.
klqb

SYSTem:PRESet and *RST have no effect on status structure registers and
queues.

Table 10-1
Common and SCPI commands — reset registers and clear queues
Commands

Description

Ref

Reset all bits of the following event registers to 0:
Standard event register
Operation event register
Measurement event register
Questionable event register
STATus subsystem:
Reset all bits of the following enable registers to 0:
Operation event enable register
Measurement event enable register
Questionable event enable register

Note 1

To clear error queue:
*CLS

Clear all messages from error queue

Note 2

STATus
:QUEue
:CLEar
SYSTem
:ERRor
:CLEar

STATus subsystem:
Error queue:
Clear messages from error queue
SYSTem subsystem:
Error queue:
Clear messages from error queue

To reset registers:
*CLS

STATus
:PRESet

Note 1

Note 3

Notes:
1. The standard event enable register is not reset by STATus:PRESet or *CLS. Send the 0 parameter value with
*ESE to reset all bits of that enable register to 0 (see “Status byte and service request (SRQ),” page 10-7).
2. STATus:PRESet has no effect on the error queue.
3. Use either of the two clear commands to clear the error queue.

Model 6487 Reference Manual

Status Structure

10-5

Programming and reading registers
Programming enable registers
The only registers that can be programmed by the user are the enable registers. All other
registers in the status structure are read-only registers. The following explains how to
ascertain the parameter values for the various commands used to program enable registers.
The actual commands are covered later in this section (Table 10-3 through Table 10-6).
A command to program an event enable register is sent with a parameter value that determines the desired state (0 or 1) of each bit in the appropriate register. An enable register
can be programmed using any of the following data formats for the parameter value:
binary, decimal, hexadecimal, or octal.
The bit positions of the register (Figure 10-1) indicate the binary parameter value. For
example, if you wish to sets bits B4, B3, and B1, the binary value would be 11010 (where
B4=1, B3=1, B1=1 and all other bits are 0). When you use one of the other formats, convert the binary number to its decimal, hexadecimal, or octal equivalent:
Binary 11010 = Decimal 26 = Hexadecimal 1A = Octal 32
Note that Figure 10-2 includes the decimal weight for each register bit. To set bits B4, B3,
and B1, the decimal parameter value would be the sum of the decimal weights for those
bits (16+8+2 = 26).
Figure 10-2
16-bit status register
A. Bits 0 through 7
Bit Position
Binary Value

0/1

128
(27 )

64
(26 )

32
(25 )

16
(24 )

8
(23 )

4
(22 )

2
(21 )

1
(20 )

B15

B14

B13

B12

B11

B10

0/1

32768
(215 )

16384
(214 )

8192
(213 )

4096
(212 )

2048
(211 )

1024
(210 )

512
(29 )

256
(28 )

Decimal Weights

B. Bits 8 through 15
Bit Position
Binary Value
Decimal Weights

The (non-decimal numeric) parameter type is used to send non-decimal values.
These values require a header (#B, #H, or #Q) to identify the data format being sent. The
letter in the header can be upper or lower case. The (numeric representation for-

10-6

Status Structure

Model 6487 Reference Manual

mat) parameter type is used to send decimal values and does not use a header. The following examples show the proper parameter syntax for setting bits B5, B3, and B2:
#b101100
#h2C
#q54
44

Binary format ( parameter type)
Hexadecimal format ( parameter type)
Octal format ( parameter type)
Decimal format ( parameter type)

Valid characters for the non-decimal parameter values are shown as follows:
Format
Binary
Hexadecimal
Octal

Valid Characters
1’s and 0’s
0 through 9 and A through F
0 through 7

Reading registers
Any register in the status structure can be read by using the appropriate query (?) command. The following explains how to interpret the returned value (response message). The
actual query commands are covered later in this section (Table 10-3 through Table 10-6).
The response message will be a value that indicates which bits in the register are set. That
value (if not already binary) will have to be converted to its binary equivalent. For example, for a binary value of 100101, bits B5, B2, and B0 are set.
The returned value can be in the binary, decimal, hexadecimal, or octal format. The
FORMat:SREGister command is used to select the data format for the returned value
(Table 10-2).
For non-decimal formats, one of the following headers will accompany the returned value
to indicate which format is selected:
#B = Header for binary values,
#H = Header for hexadecimal values,
#Q = Header for octal values.
Table 10-2
SCPI command — data formats for reading status registers
Command
:FORMat
:SREGister

Description
FORMat subsystem
Select data format for reading status registers:
= ASCii
Decimal format
HEXadecimal Hexadecimal format
OCTal
Octal format
BINary
Binary format

Default
ASCii

Model 6487 Reference Manual

Status Structure

10-7

Status byte and service request (SRQ)
Service request is controlled by two 8-bit registers: the status byte register and the service
request enable register. Figure 10-3 shows the structure of these registers.
Figure 10-3
Status byte and service request
Status Summary Messages (6)

Service
Request
Generation

RQS
OSB (B6)
* STB?
(B7)
Serial Poll
MSS

ESB MAV QSB EAV
(B5) (B4) (B3) (B2)

(B1)

MSB Status Byte
(B0) Register

&
&
&
OR

&
&
&

* SRE
* SRE?

Decimal
Weights

OSB
ESB
(B7) (B6) (B5)

128
(27)

32
(25)

MAV QSB EAV
(B4) (B3) (B2)

16
(24)

8
(23)

4
(22)

OSB = Operation Summary Bit
MSS = Master Summary Status
RQS = Request for Service
ESB = Event Summary Bit
MAV = Message Available
QSB = Questionable Summary Bit
EAV = Error Available
MSB = Measurement Summary Bit

MSB Service Request
(B1) (B0) Enable Register

1
(20)
& = Logical AND
OR = Logical OR

Status byte register
The summary messages from the status registers and queues are used to set or clear the
appropriate bits (B0, B2, B3, B4, B5, and B7) of the status byte register. These summary
bits do not latch and their states (0 or 1) are solely dependent on the summary messages
(0 or 1). For example, if the standard event register is read, its register will clear. As a
result, its summary message will reset to 0, which in turn will reset the ESB bit in the
status byte register.

10-8

Status Structure

Model 6487 Reference Manual

The bits of the status byte register are described as follows:
•
•
•
•
•
•
•
•

Bit B0, measurement status (MSB) — Set summary bit indicates that an enabled
measurement event has occurred.
Bit B1 — Not used.
Bit B2, error available (EAV) — Set summary bit indicates that an error or status
message is present in the error queue.
Bit B3, questionable summary bit (QSB) — Set summary bit indicates that an
enabled questionable event has occurred.
Bit B4, message available (MAV) — Set summary bit indicates that a response
message is present in the output queue.
Bit B5, event summary bit (ESB) — Set summary bit indicates that an enabled
standard event has occurred.
Bit B6, request service (RQS)/master summary status (MSS) — Set bit indicates
that an enabled summary bit of the status byte register is set.
Bit B7, operation summary (OSB) — Set summary bit indicates that an enabled
operation event has occurred.

Depending on how it is used, bit B6 of the status byte register is either the request for service (RQS) bit or the master summary status (MSS) bit:
•

•

When using the serial poll sequence of the Model 6487 to obtain the status byte
(a.k.a. serial poll byte), B6 is the RQS bit. See “Serial polling and SRQ,” page 10-9
for details on using the serial poll sequence.
When using the *STB? command (Table 10-3) to read the status byte, B6 is the
MSS bit.

Service request enable register
The generation of a service request is controlled by the service request enable register.
This register is programmed by you and is used to enable or disable the setting of bit B6
(RQS/MSS) by the status summary message bits (B0, B2, B3, B4, B5, and B7) of the status byte register. As shown in Figure 10-3, the summary bits are logically ANDed (&)
with the corresponding enable bits of the service request enable register. When a set (1)
summary bit is ANDed with an enabled (1) bit of the enable register, the logic “1” output
is applied to the input of the OR gate and, therefore, sets the MSS/RQS bit in the status
byte register.
The individual bits of the service request enable register can be set or cleared by using the
*SRE common command. To read the service request enable register, use the *SRE?
query command. The service request enable register clears when power is cycled or a
parameter value of 0 is sent with the *SRE command (i.e. *SRE 0). The commands to program and read the SRQ enable register are listed in Table 10-3.

Model 6487 Reference Manual

Status Structure

10-9

Serial polling and SRQ
Any enabled event summary bit that goes from 0 to 1 will set bit B6 and generate an SRQ
(service request). In your test program, you can periodically read the status byte to check
if an SRQ has occurred and what caused it. If an SRQ occurs, the program can, for example, branch to an appropriate subroutine that will service the request.
Typically, SRQs are managed by the serial poll sequence of the Model 6487. If an SRQ
does not occur, bit B6 (RQS) of the status byte register will remain cleared and the program will simply proceed normally after the serial poll is performed. If an SRQ does
occur, bit B6 of the status byte register will set and the program can branch to a service
subroutine when the SRQ is detected by the serial poll.
The serial poll automatically resets RQS of the status byte register. This allows subsequent
serial polls to monitor bit B6 for an SRQ occurrence generated by other event types. After
a serial poll, the same event can cause another SRQ, even if the event register that caused
the first SRQ has not been cleared.
The serial poll does not clear MSS. The MSS bit stays set until all status byte summary
bits are reset.

SPE, SPD (serial polling)
The SPE, SPD general bus command is used to serial poll the Model 6487. Serial polling
obtains the serial poll byte (status byte). Typically, serial polling is used by the controller
to determine which of several instruments has requested service with the SRQ line.

Status byte and service request commands
The commands to program and read the status byte register and service request enable register are listed in Table 10-3. For details on programming and reading registers, see “Programming enable registers,” page 10-5 and “Reading registers,” page 10-6.
To reset the bits of the service request enable register to 0, use 0 as the parameter value for
the *SRE command (i.e. *SRE 0).
Table 10-3
Common commands — status byte and service request enable registers
Command
*STB?
*SRE or

*SRE?

Description
Read status byte register.
Program the service request enable register:
= #Bxx…x Binary format (each x = 1 or 0)
= #Hx
Hexadecimal format (x = 0 to FF)
= #Qx
Octal format (x = 0 to 377)
= 0 to 255
Decimal format
Read the service request enable register.

Note: *CLS and STATus:PRESet have no effect on the service request enable register.

Default
(Note)

10-10

Status Structure

Model 6487 Reference Manual

Programming example — set MSS (B6) when error occurs
The first command of the following sequence enables EAV (error available). When an
invalid command is sent (line 4), bits B2 (EAV) and B6 (MSS) of the status byte register
set to 1. The last command reads the status byte register using the binary format (which
directly indicates which bits are set). The command to select format (FORMat:SREGister)
is documented in Table 10-2. To determine the exact nature of the error, you will have to
read the error queue (see “Queues,” page 10-17).
*CLS
*SRE 4
FORM:SREG BIN
BadCommand
*STB?

'
'
'
'
'

Clear Error Queue.
Enable EAV.
Select binary format.
Generate error.
Read Status Byte Register.

Status register sets
As shown in Figure 10-1, there are four status register sets in the status structure of the
Model 6487: standard event status, operation event status, measurement event status, and
questionable event status.

Register bit descriptions
Standard event status
The used bits of the standard event register (Figure 10-4) are described as follows:
•

•
•
•
•

Bit B0, operation complete (OPC) — Set bit indicates that all pending selected
device operations are completed and the Model 6487 is ready to accept new commands. This bit only sets in response to the *OPC? query command. See
Section 11 for details on *OPC and *OPC?.
Bit B2, query error (QYE) — Set bit indicates that you attempted to read data
from an empty output queue.
Bit B3, device-dependent error (DDE) — Set bit indicates that an instrument
operation did not execute properly due to some internal condition.
Bit B4, execution error (EXE) — Set bit indicates that the Model 6487 detected
an error while trying to execute a command.
Bit B5, command error (CME) — Set bit indicates that a command error has
occurred.
Command errors include:
— IEEE-488.2 syntax error — The Model 6487 received a message that does not follow the defined syntax of the IEEE-488.2 standard.
— Semantic error — The Model 6487 received a command that was misspelled or
received an optional IEEE-488.2 command that is not implemented.
— The instrument received a Group Execute Trigger (GET) inside a program message.

Model 6487 Reference Manual

Status Structure

10-11

Figure 10-4
Standard event status
*ESR?

(B15 - B8)

PON URQ CME EXE DDE QYE
OPC Standard Event
(B7) (B6) (B5) (B4) (B3) (B2) (B1) (B0) Register

&
&
&
To ESB bit
of Status Byte
Register

&
&
&

*ESE
*ESE?

Decimal
Weights

(B15 - B8)

PON URQ CME EXE DDE QYE
OPC Standard Event
(B7) (B6) (B5) (B4) (B3) (B2) (B1) (B0) Enable Register

128
(27)

64
(26)

32
(25)

PON = Power On
URQ = User Request
CME = Command Error
EXE = Execution Error
DDE = Device-Dependent Error
QYE = Query Error
OPC = Operation Complete

•
•

16
(24)

8
(23)

4
(22)

1
(20)

& = Logical AND
OR = Logical OR

Bit B6, user request (URQ) — Set bit indicates that the LOCAL key on the
Model 6487 front panel was pressed.
Bit B7, power ON (PON) — Set bit indicates that Model 6487 has been turned off
and turned back on since the last time this register has been read.

10-12

Status Structure

Model 6487 Reference Manual

Operation event status
The used bits of the operation event register (Figure 10-5) are described as follows:
•
•
•
•
•
•

Bit B0, calibrating (CAL) — Set bit indicates that the Model 6487 is calibrating.
Bit B1, A-V Ohms — Set bit indicates that alternating voltage ohms is running.
Bit B3, Sweeping — Set bit indicates that a voltage sweep is running.
Bit B5, waiting for trigger event (Trig) — Set bit indicates that the Model 6487 is
in the trigger layer waiting for a TLINK trigger event to occur.
Bit B6, waiting for arm event (Arm) — Set bit indicates that the Model 6487 is in
the arm layer waiting for an arm event to occur.
Bit B10, idle state (Idle) — Set bit indicates the Model 6487 is in the idle state.

Figure 10-5
Operation event status
:CONDition?

[:EVENt]?

(B15-B11)

Idle
(B10)

(B9-B7)

Arm Trig
(B6) (B5)

(B4)

Swp
(B3)

(B2)

A-V
(B1)

Cal Operation Condition
(B0) Register

(B15-B11)

Idle
(B10)

(B9-B7)

Arm Trig
(B6) (B5)

(B4)

Swp
(B3)

(B2)

A-V
(B1)

Cal Operation Event
(B0) Register

&
To OPC bit
of Status Byte
Register

&
&

:ENABle
:ENABle?

Decimal
Weights

(B15-B11)

Idle
(B10)

(B9-B7)

1024
(210)
Idle = In Idle
Trig = Waiting for trigger event
Arm = Waiting for arm event
Cal = Calibrating
A-V = A-V Ohms
Swp = Sweep running

Arm Trig
(B6) (B5)

(B4)

Swp
(B3)

(B2)

A-V
(B1)

Cal Operation Event
(B0) Enable Register

64
(26)

16
(24)

8
(23)

4
(22)

2
(21)

1
(20)

32
(25)

& = Logical AND
OR = Logical OR

Model 6487 Reference Manual

Status Structure

10-13

Measurement event status
The used bits of the measurement event register (Figure 10-6) are described as follows:
Bit B1, low limit 1 fail (LL1F) — Set bit indicates that the low limit 1 test has
failed.
Bit B2, high limit 1 fail (HL1F) — Set bit indicates that the high limit 1 test has
failed.

•
•

Figure 10-6
Measurement event status
:CONDition?

INT IOV BFL BAV ROF RAV
VSC
(B15) (B14) (B13) (B12) (B11) (B10) (B9) (B8) (B7) (B6)

LP HL2F LL2F HL1F LL1F
(B5) (B4) (B3) (B2) (B1) (B0)

Measurement
Condition
Register

[:EVENt]?

INT IOV BFL BAV ROF RAV
VSC
(B15) (B14) (B13) (B12) (B11) (B10) (B9) (B8) (B7) (B6)

LP HL2F LL2F HL1F LL1F
(B5) (B4) (B3) (B2) (B1) (B0)

Measurement
Event Register

&
&
&
&
To MSB
bit of Status
Byte Register

&
&

&
&
&
&
&
&

INT IOV BFL BAV ROF RAV
VSC
:ENABle
(B15) (B14) (B13) (B12) (B11) (B10) (B9) (B8) (B7) (B6)
:ENABle?

Decimal
Weights

16384

(214)

2048 1024 512
(211) (210) (29)
BFL = Buffer Full
BAV = Buffer Available
ROF = Reading Overflow
RAV = Reading Available
LP = Limits Pass
IOV = Input Overvoltage

256
(28)

128
(27)

64
(26)

LP HL2F LL2F HL1F LL1F
(B5) (B4) (B3) (B2) (B1) (B0)

32
(25)

16
(24)

8
(23)

4
(22)

HL2F = High Limit 2 Fail
& = Logical AND
LL2F = Low Limit 2 Fail
OR = Logical OR
HL1F = High Limit 1 Fail
LL1F = Low Limit 1 Fail
INT = Interlock Asserted
VSC = Voltage Source Compliance

2
(21)

Measurement
Event Enable
Register

10-14

Status Structure

•
•
•
•
•
•
•

•
•
•

Model 6487 Reference Manual

Bit B3, low limit 2 fail (LL2F) — Set bit indicates that the low limit 2 test has
failed.
Bit B4, high limit 2 fail (HL2F) — Set bit indicates that the high limit 2 test has
failed.
Bit B5, limits pass (LP) — Set bit indicates that all limit tests passed.
Bit B6, reading available (RAV) — Set bit indicates that a reading was taken and
processed.
Bit B7, reading overflow (ROF) — Set bit indicates that the reading exceeds the
selected measurement range of the Model 6487.
Bit B8, buffer available (BAV) — Set bit indicates that there are at least two
readings in the buffer.
Bit B9, buffer full (BFL) — Set bit indicates that the buffer is full. This bit will
also be set when a voltage sweep has been completed (Section 6), and if the
programmed number of A-V ohms cycles have been taken (Section 3).
Bit B10, input overvoltage (IOV) — Set bit indicates there is an input over
voltage condition.
Bit B11, output interlock asserted (INT) — Set bit indicates that the output
interlock is asserted and the voltage source output cannot be turned on.
Bit B14, voltage source compliance (VSC) — Set bit indicates that the voltage
source is in compliance.

Questionable event status
The used bits of the questionable event register (Figure 10-7) are described as follows:
•

•

Bit B7, calibration summary (Cal) — Set bit indicates that an invalid calibration
constant was detected during the power-up sequence. This error will clear after
successful calibration of the Model 6487.
Bit B14, command warning (Warn) — Set bit indicates that a signal oriented
measurement command parameter has been ignored.

Model 6487 Reference Manual

Status Structure

10-15

Figure 10-7
Questionable event status
:CONDition?

[:EVENt]?

To QSB bit
of Status Byte
Register

(B15)

Warn
(B14)

(B13-B8)

Cal
(B7)

(B6-B0)

Questionable
Condition Register

(B15)

Warn
(B14)

(B13-B8)

Cal
(B7)

(B6-B0)

Questionable
Event Register

(B6-B0)

Questionable Event
Enable Register

:ENABle
:ENABle?

(B15)

Warn
(B14)

(B13-B8)

16384
(214)

Decimal
Weights

Cal
(B7)

128
(27)

Warn = Command Warning
Cal = Calibration Summary

& = Logical AND
OR = Logical OR

Condition registers
As Figure 10-1 shows, each status register set (except the standard event register set) has a
condition register. A condition register is a real-time, read-only register that constantly
updates to reflect the present operating conditions of the instrument. For example, while
the Model 6487 is in the idle state, bit B10 (Idle) of the operation condition register will be
set. When the instrument is taken out of idle, bit B10 clears.
The commands to read the condition registers are listed in Table 10-4. For details on reading registers, see “Reading registers,” page 10-6.
Table 10-4
Common and SCPI commands — condition registers
Command
STATus
:OPERation:CONDition?
:MEASurement:CONDition?
:QUEStionable:CONDition?

Description
STATus subsystem:
Read operation condition register.
Read measurement condition register.
Read questionable condition register.

10-16

Status Structure

Model 6487 Reference Manual

Event registers
As Figure 10-1 shows, each status register set has an event register. When an event occurs,
the appropriate event register bit sets to 1. The bit remains latched to 1 until the register is
reset. Reading an event register clears the bits of that register. *CLS resets all four event
registers.
The commands to read the event registers are listed in Table 10-5. For details on reading
registers, see “Reading registers,” page 10-6.
Table 10-5
Common and SCPI commands — event registers
Command

Description

*ESR?

Read standard event status register.

STATus
:OPERation:[:EVENt]?
:MEASurement:[:EVENt]?
:QUEStionable:[:EVENt]?

STATus subsystem:
Read operation event register.
Read measurement event register.
Read questionable event register.

Note: Power-up and *CLS resets all bits of all event registers to 0. STATus:PRESet has no effect.

Event enable registers
As Figure 10-1 shows, each status register set has an enable register. Each event register
bit is logically ANDed (&) to a corresponding enable bit of an enable register. Therefore,
when an event bit is set and the corresponding enable bit is set (as programmed by the
user), the output (summary) of the register will set to 1, which in turn sets the summary bit
of the status byte register.
The commands to program and read the event enable registers are listed in Table 10-6. For
details on programming and reading registers, see “Programming enable registers,”
page 10-5 and “Reading registers,” page 10-6.
klqb

The bits of any enable register can be reset to 0 by sending the
0 parameter value with the appropriate enable command
(i.e. STATus:OPERation:ENABle 0).

Model 6487 Reference Manual

Status Structure

10-17

Table 10-6
Common and SCPI commands — event enable registers
Command

Description

*ESE or
*ESE?

Program standard event enable register (see “Parameters”).
Read standard event enable register.

STATus
:OPERation
:ENABle or
:ENABle?
:MEASurement
:ENABle or
:ENABle?
:QUEStionable
:ENABle or
:ENABle?
Parameters:

STATus subsystem:
Operation event enable register:
Program enable register (see “Parameters”).
Read enable register.
Measurement event enable register:
Program enable register (see “Parameters”).
Read enable register.
Questionable event enable register:
Program enable register (see “Parameters”).
Read measurement event enable register.

= #Bxx…x
= #Hx
= #Qx
= 0 to 65535

Binary format (each x = 1 or 0)
Hexadecimal format (x = 0 to FFFF)
Octal format (x = 0 to 177777)
Decimal format

Note: Power-up and STATus:PRESet resets all bits of all enable registers to 0. *CLS has no effect.

Programming example — program and read registers
This command sequence programs and reads the measurement registers. Registers are
read using the binary format (which directly indicates which bits are set). The command to
select format (FORMat:SREGister) is documented in Table 10-2.
FORM:SREG BIN
STAT:MEAS:ENAB 512
STAT:MEAS:COND?
STAT:MEAS?

'
'
'
'

Select binary format to read registers.
Enable BFL (buffer full).
Read Measurement Condition Register.
Read Measurement Event Register.

Queues
The Model 6487 uses two queues which are first-in, first-out (FIFO) registers:
•
•

Output queue — Used to hold reading and response messages.
Error queue — Used to hold error and status messages.

The Model 6487 status model (Figure 10-1) shows how the two queues are structured with
the other registers.

10-18

Status Structure

Model 6487 Reference Manual

Output queue
The output queue holds data that pertains to the normal operation of the instrument. For
example, when a query command is sent, the response message is placed in the output
queue.
When data is placed in the output queue, the message available (MAV) bit in the status
byte register sets. A data message is cleared from the output queue when it is read. The
output queue is considered cleared when it is empty. An empty output queue clears the
MAV bit in the status byte register.
A message is read from the output queue by addressing the Model 6487 to talk after the
appropriate query is sent.

Model 6487 Reference Manual

Status Structure

10-19

Error queue
The error queue holds error and status messages. When an error or status event occurs, a
message that defines the error/status is placed in the error queue.
When a message is placed in the error queue, the error available (EAV) bit in the status
byte register is set. An error/status message is cleared from the error queue when it is read.
The error queue is considered cleared when it is empty. An empty error queue clears the
EAV bit in the status byte register.
The error queue holds up to 10 error/status messages. The commands to read the error
queue are listed in Table 10-7. When you read a single message in the error queue, the
“oldest” message is read and then removed from the queue. If the queue becomes full, the
message “350, ‘queue overflow’” will occupy the last memory location. On power-up, the
error queue is empty. When empty, the message “0, No Error” is placed in the queue.
Messages in the error queue are preceded by a code number. Negative (-) numbers are
used for SCPI defined messages and positive (+) numbers are used for Keithley defined
messages. The messages are listed in Appendix B. As shown in Table 10-7, there are commands to read the entire message (code and message) or the code only.
On power-up, all error messages are enabled and will go into the error queue as they occur.
Status messages are not enabled and will not go into the queue. As listed in Table 10-7,
there are commands to enable and/or disable messages. For these commands, the
parameter is used to specify which messages to enable or disable. The messages are specified by their codes. The following examples show various forms for using the
parameter.

= (-110)
= (-110:-222)
= (-110:-222, -220)

Single message
Range of messages (-110 through -222)
Range entry and single entry (separated by a comma)

When you enable messages, messages not specified in the list are disabled. When you disable messages, each listed message is removed from the enabled list.
To prevent all messages from entering the error queue, send the enable command along
with the null list parameter as follows: STATus:QUEue:ENABle ().

10-20

Status Structure

Model 6487 Reference Manual

Table 10-7
SCPI commands — error queue
Command

Description

STATus
:QUEue
[:NEXT]?
:ENABle
:ENABle?
:DISable
:DISable?
:CLEar

STATus subsystem:
Read error queue:
Read and clear oldest error/status (code and message).
Specify error and status messages for error queue.
Read the enabled messages.
Specify messages not to be placed in queue.
Read the disabled messages.
Clear messages from error queue.

SYSTem
:ERRor
[:NEXT]?
:ALL?
:COUNt?
:CODE
[:NEXT]?
:ALL?

SYSTem subsystem:
Read error queue:
Read and clear oldest error/status (code and message).
Read and clear all errors/status (code and message).
Read the number of messages in queue.
Code numbers only:
Read and clear oldest error/status (code only).
Read and clear all errors/status (codes only).

Notes:
1. Power-up and *CLS empties the error queue. STATus:PRESet has no effect.
2. Power-up enables error messages and disables status messages. *CLS and STATus:PRESet have no effect.

Programming example — read error queue
The following command reads the error queue:
STAT:QUE?

' Read Error Queue.

Default
(Note 1)
(Note 2)
(Note 2)

(Note 1)

Common Commands
•

Common commands — This section lists and describes the common commands.

11-2

Common Commands

Model 6487 Reference Manual

Common commands
Common commands (summarized in Table 11-1) are device commands that are common
to all devices on the bus. These commands are designated and defined by the IEEE-488.2
standard.
Table 11-1
IEEE-488.2 common commands and queries
Mnemonic
*CLS
*ESE
*ESE?
*ESR?
*IDN?

Name
Clear status
Event enable command
Event enable query
Event status register query
Identification query

Description

Clears all event registers and error queue.
Program the standard event enable register.
Read the standard event enable register.
Read the standard event enable register and clear it.
Returns the manufacturer, model number, serial
number, and firmware revision levels of the unit.
*OPC
Operation complete command
Set the operation complete bit in the standard event
register after all pending commands have been
executed.
*OPC?
Operation complete query
Places an ASCII “1” into the output queue when all
pending selected device operations have been
completed.
*OPT?
Option query
Returns model number of any installed options.
*RCL Recall command
Returns Model 6487 to the user-saved setup.
*RST
Reset command
Returns Model 6487 to the *RST default
conditions.
*SAV Save command
Saves the present setup as the user-saved setup.
*SRE Service request enable command Programs the service request enable register.
*SRE?
Service request enable query
Reads the service request enable register.
*STB?
Status byte query
Reads the status byte register.
*TRG
Trigger command
Sends a bus trigger to Model 6487.
*TST?
Self-test query
Performs a checksum test on ROM and returns the
result.
*WAI
Wait-to-continue command
Wait until all previous commands are executed.

Ref
Section 10
Section 10
Section 10
Section 10
A
B

C
D
C
Section 10
Section 10
Section 10
E
F
G

Model 6487 Reference Manual

Common Commands

A) IDN? — identification query

11-3

Reads identification code

The identification code includes the manufacturer, model number, serial number, and firmware revision levels and is sent in the following format:
KEITHLEY INSTRUMENTS INC., MODEL 6487, xxxxxxx, yyyyy/zzzzz/w
Where: xxxxxxx is the serial number.
yyyyy/zzzzz is the firmware revision levels of the digital board ROM and
display board ROM. Note that yyyyy also provides build date and time
information. w is the board revision level.

B) OPC — operation complete
OPC? — operation complete query

Sets OPC bit
Places a “1” in output queue

When *OPC is sent, the OPC bit in the standard event register will set after all pending
command operations are complete. When *OPC? is sent, an ASCII “1” is placed in the
output queue after all pending command operations are complete.
Typically, either one of these commands is sent after the INITiate command. The INITiate
command is used to take the instrument out of idle in order to perform measurements.
While operating within the trigger model layers, all sent commands (except DCL, SDC,
IFC, SYSTem:PRESet, *RST, GET, and ABORt) will not execute.
After all programmed operations are completed, the instrument returns to the idle state at
which time all pending commands (including *OPC and/or *OPC?) are executed. After
the last pending command is executed, the OPC bit and/or an ASCII “1” is placed in the
output queue.
Programming example — The following command sequence will perform 10 measurements. After the measurements are completed (in approximately 10 seconds), an ASCII
“1” will be placed in the output queue.
*RST
TRIG:DEL 1
ARM:COUN 10
INIT
*OPC?

'
'
'
'
'

Return 6487 to RST defaults (idle).
Set trigger delay for 1 second.
Program for 5 measurements and stop.
Start measurements.
Send *OPC?.

11-4

Common Commands

Model 6487 Reference Manual

C) SAV — save
RCL — recall
Parameters

Save present setup in memory
Return to setup stored in memory

0 = Memory location 0
1 = Memory location 1
2 = Memory location 2

Use the *SAV command to save the present instrument setup configuration in memory for
later recall. Any control affected by *RST can be saved by the *SAV command. The *RCL
command is used to restore the instrument to the saved setup configuration. Three setup
configurations can be saved and recalled.
The Model 6487 ships from the factory with SYSTem:PRESet defaults loaded into the
available setup memory. If a recall error occurs, the setup memory defaults to the
SYSTem:PRESet values.
Programming example:
*SAV 2
*RST
*RCL 2

' Save present setup in memory location 2.
' Set 6487 to RST defaults.
' Return (recall) 6487 to setup stored in memory location 2.

D) RST — reset

Return Model 6487 to RST defaults

When the *RST command is sent, the Model 6487 performs the following operations:
1.

Returns Model 6487 to the RST default conditions (see “Default” column of SCPI
tables).
Cancels all pending commands.
Cancels response to any previously received *OPC and *OPC? commands.

2.
3.

TRG — trigger

Send bus trigger to Model 6487

Use the *TRG command to issue a GPIB trigger to the Model 6487. It has the same effect
as a group execute trigger (GET).
Use the *TRG command as an event to control operation. The Model 6487 reacts to this
trigger if BUS is the programmed arm control source. The control source is programmed
from the TRIGger subsystem.
klqb

Details on triggering are covered in Section 7.

Programming example — The following command sequence configures the Model 6487
to be controlled by bus triggers. The last line, which sends a bus trigger, triggers one measurement. Each subsequent bus trigger will also trigger a single measurement.
*RST
ARM:SOUR BUS
ARM:COUN INF
INIT
*TRG

'
'
'
'
'

Restore RST defaults.
Select BUS control source.
Set arm layer count to infinite.
Take 6487 out of idle.
Trigger one measurement.

Model 6487 Reference Manual

TST? — self-test query

Common Commands

11-5

Run self-test and read result

Use this query command to perform a checksum test on ROM. The command places the
coded result (0 or 1) in the output queue. When the Model 6487 is addressed to talk, the
coded result is sent from the output queue to the computer.
A returned value of zero (0) indicates that the test passed and a value of one (1) indicates
that the test failed.

G) WAI — wait-to-continue

Wait until previous commands are completed

Effectively, the *WAI command is a No-Op (no operation) for the Model 6487 and thus,
does not need to be used.
Two types of device commands exist:
•
•

Sequential commands — A command whose operations are allowed to finish
before the next command is executed.
Overlapped commands — A command that allows the execution of subsequent
commands while device operations of the overlapped command are still in
progress.

The *WAI command is used to suspend the execution of subsequent commands until the
device operations of all previous overlapped commands are finished. The *WAI command
is not needed for sequential commands.

SCPI Signal Oriented
Measurement Commands

12-2

SCPI Signal Oriented Measurement Commands

Model 6487 Reference Manual

The signal oriented measurement commands are used to acquire readings. You can use
these high level instructions to control the measurement process. These commands are
summarized in Table 12-1.
klqb

The readings acquired by these commands depend on which data elements are
selected. (See Table 13-3 for details.)

Table 12-1
Signal oriented measurement command summary
Command
CONFigure[:]
CONFigure?
FETCh?
READ?
MEASure[:]?

Description
Places Model 6487 in a “one-shot” measurement
mode. = CURR[:DC]
Queries the selected function. Returns ‘CURR’.
Requests the latest reading(s).
Performs an INITiate and a :FETCh?.
Performs a CONFigure: and a :READ?.

Ref
A

B
C
D

A) CONFigure[:]

Configure Model 6487 for “one-shot” measurements

= CURRent[:DC]

Configure current

This command configures the instrument for “one-shot” measurements. Each subsequent
READ? command will then trigger a single measurement and acquire the reading (see
READ? for details).
If the instrument is in idle, this command will execute immediately. If the instrument is not
in idle, execution of the command will execute when the operation returns to the idle state.
When this command is executed, the Model 6487 will be configured as follows:
•
•
•
•
•
•
•
•
•

The specified function is selected.
All controls related to the selected function are defaulted to the *RST values.
The event control sources of the trigger model are set to immediate.
The arm and trigger count values of the trigger model are set to one.
The delay of the trigger model is set to zero.
The Model 6487 is placed in the idle state.
All math calculations are disabled.
Buffer operation is disabled. A storage operation presently in process will be
aborted.
Autozero is enabled.

This command is automatically asserted when the :MEASure? command is sent.

Model 6487 Reference Manual

SCPI Signal Oriented Measurement Commands

12-3

Programming example — The following command sequence selects and configures the
Model 6487 for “one-shot” measurements. Each subsequent READ? triggers a single
measurement and requests the reading.
CONF:CURR
READ?

B) FETCh?

' Perform CONFigure operations.
' Trigger measurement and request reading.

Request latest reading

This command requests the latest post-processed readings. After sending this command
and addressing the Model 6487 to talk, the readings are sent to the computer. This command does not affect the instrument setup.
This command does not trigger a measurement. The command simply requests the last
group of readings. Note that this command can repeatedly return the same readings. Until
there is a new reading(s), this command continues to return the old reading(s). If your
application requires a “fresh” reading, use the :READ? command.
This command is automatically asserted when the :READ? or :MEASure? command is
sent.

C) READ?

Trigger measurement(s) and request reading(s)

This command is used to trigger and acquire readings. The number of readings depends on
how the trigger model is configured. For example, if configured for 20 measurements (arm
count 1, trigger count 20), 20 sets of readings will be acquired.
When this command is sent, the following commands execute in the order they are
presented:
•
•

INITiate
FETCh?

If the instrument is in the idle state, INITiate takes the instrument out of idle to perform
the programmed number of measurements. If the instrument is not in the idle state, execution of this command will wait until it goes back into idle.
The FETCh? command is executed to acquire the reading(s). The readings are sent to the
computer when the Model 6487 is addressed to talk.
klqb

If the instrument is programmed to perform an infinite number of measurements
(arm count or trigger count set to infinite), you cannot use the READ? command
to trigger and acquire readings. Use INITiate to start (trigger) the measurement
process, send ABORt to abort the measurement process, and then use
SENSe:DATA[:LATest]? to return the last (latest) reading.

12-4

SCPI Signal Oriented Measurement Commands

D) MEASure[:]?
= CURRent[:DC]

Model 6487 Reference Manual

Configure and perform “one-shot” measurement
Measure current

This command combines all of the other signal oriented measurement commands to perform a “one-shot” measurement and acquire the reading.
When this command is sent, the following commands execute in the order that they are
presented.
•
•

CONFigure:
READ?

When :CONFigure is executed, the instrument goes into a “one-shot” measurement mode.
See CONFigure for details.
When READ? is executed, its operations will then be performed. In general, an INITiate is
executed to perform the measurement and a FETCh? is executed to acquire the reading.
See :READ? for details.

DISPlay, FORMat, and SYSTem
•

DISPlay subsystem — Covers the SCPI commands that are used to control the
display.

•

FORMat subsystem — Covers the SCPI commands to configure the format that
readings are sent over the bus.

•

SYSTem subsystem — Covers miscellaneous SCPI commands.

13-2

DISPlay, FORMat, and SYSTem

Model 6487 Reference Manual

DISPlay subsystem
The commands in this subsystem are used to control the display over the bus.
Table 13-1
SCPI commands — display
Command

Description

:DISPlay
:DIGits

Default

Ref

Section 4

(see Note)

Set display resolution: 4 to 7.

:DIGits?
:ENABle
:ENABle?
[:WINDow[1]]
:TEXT
[:DATA]
[:DATA]?
:STATe

Query display resolution.
Turn front panel display on or off.
Query front panel display status.
Path to control user text messages:

(see Note)
Define ASCII message “a” (up to 12 characters).
Query defined ASCII message.
Enable or disable text message mode.

B
C

Note: *RST and SYSTem:PRESet have no effect on the display circuitry and user-defined text messages.

A) DISPlay:ENABle
With front panel circuitry turned off, the instrument operates at a higher speed. While disabled, the display is frozen and all front panel controls (except LOCAL) are disabled. Normal display operations can be resumed by using :ENABle to enable the display, pressing
the LOCAL key, or cycling power.

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13-3

B) DISPlay:TEXT[:DATA]
Message Types: String
Indefinite Block
Definite Block

‘aa…a’ or “aa…a”
#0aa…a
#XYaa…a

where: Y = number of characters in message (up to 12)
X = number of digits that make up Y (1 or 2)
The display message can be up to 12 characters (ASCII) long. A space is counted as a
character. Excess message characters result in an error. Note that for the string type, the
message must be enclosed by single or double quotes.
An indefinite block message must be the only command in the program message or the
last command in the program message. If you include a command after an indefinite block
message (on the same line), it will be treated as part of the message and is displayed
instead of executed.

C) DISPlay:TEXT:STATe
When the text message mode is enabled, a defined message is displayed. When disabled,
the message is removed from the display.
GPIB operation — A user-defined message remains displayed only as long as the instrument is in remote. Taking the instrument out of remote (by pressing LOCAL or sending
the GTL (go to local) command) or cycling power cancels the message and disables the
text message mode.
RS-232 operation — A user-defined message can be cancelled by sending
SYSTem:LOCal, pressing LOCAL, or cycling power.

13-4

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Model 6487 Reference Manual

FORMat subsystem
The commands in this subsystem are used to select the format for transferring data over
the bus.
Table 13-2
SCPI commands — data format
Command

Description

:FORMat
:DATA [,]
:DATA?
:ELEMents
:BORDer
:BORDer?
:SREGister
:SREGister?
:SOURce2
:SOURce2?

Default

Ref

Specify data format: ASCii, REAL, 32 or SREal. ASCii
A
Query data format.
Specify data elements: READing, UNITS,
All except
B
VSOurce, TIME, STATus, DEFault, and ALL.
VSO
Specify byte order: NORMal or SWAPped.
(see Note)
C
Query byte order.
Select data format for reading status registers:
ASC
ASCii, HEXadecimal, OCTal, or BINary.
Section 10
Query data format for reading status registers.
Select data format for reading output patterns:
ASC
Section 8
ASCii, HEXadecimal, OCTal, or BINary.
Query data format for output patterns.

Note: *RST default is NORMal. SYSTem:PRESet default is SWAPped.

A) FORMat:DATA [,]
Parameters

klqb

ASCii
= ASCII format
REAL, 32 = Binary IEEE-754 single precision format
SREal
= Binary IEEE-754 single precision format

is not used for the ASCii or SREal parameters. It is optional for the
REAL parameter. If you do not use with REAL, defaults to
32 (single precision format). The double precision format ( = 64) is
not supported by Model 6487.

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13-5

The response to READ?, FETCh?, MEASure?, TRACe:DATA?, CALC1:DATA?,
CALC2:DATA?, or CALC3:DATA? over the GPIB can be returned in either the ASCii or
binary format. All other queries are returned in ASCii, regardless of the selected format.
Over the RS-232 interface, only the ASCII format is allowed.
klqb

Regardless of which data format for output strings is selected, the instrument
will only respond to input commands using the ASCII format.

ASCII data format
The ASCII data format is in a direct readable form for the operator. Most programming
languages easily convert ASCII mantissa and exponent to other formats. However, some
speed is compromised to accommodate the conversion. Figure 13-1 shows an example
ASCII string that includes all the data elements. See :ELEMents for information on the
data elements.
Figure 13-1 also shows the byte order of the data string. Data elements not specified by the
:ELEMents command are simply not included in the string. Note that the status value is
always an integer, but it is still expressed in scientific notation.
Figure 13-1
ASCII data format
+1.040564E-06A, +2.2362990+2, +1.380000E+2, +123.4500

Reading

Units

Timestamp

Status

V-source

13-6

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Model 6487 Reference Manual

IEEE-754 single precision format
REAL 32 or SREal will select the binary IEEE-754 single precision data format.
Figure 13-2 shows the normal byte order format for each data element. For example, if
three data elements are selected, the data string for each reading conversion is made up of
three 4-byte data blocks. Note that the data string for each reading conversion is preceded
by a 2-byte header that is the binary equivalent of an ASCII # sign and 0. Figure 13-2 does
not show the byte for the terminator that is attached to the end of each data string. Note
that the byte order of the data string can be sent in reverse order.
Figure 13-2
IEEE-754 single precision data format (32 data bits)
Header

Byte 1

Byte 2

Byte 3

Byte 4

# 0
7

0 7

s = sign bit (0 = positive, 1 = negative)
e = exponent bits (8)
f = fraction bits (23)
Normal byte order shown. For swapped byte order,
bytes sent in reverse order: Header, Byte 4, Byte 3
Byte 2, Byte 1.
The header and terminator are sent only once for each READ?.

During binary transfers, never un-talk Model 6487 until after the data is read (input) to the
computer. Also, to avoid erratic operation, the readings of the data string (and terminator)
should be acquired in one piece. The header (#0) can be read separately before the rest of
the string.
The number of bytes to be transferred can be calculated as follows:
Bytes = 2 + (Rdgs × 4) + 1
where: 2 is the number of bytes for the header (#0).
Rdgs is the product of the number of selected data elements, arm count and
trigger count.
4 is the number of bytes for each reading.
1 is the byte for the terminator.
For example, assume the instrument is configured to perform 10 measurements and send
them to the computer using the binary format:
Bytes = 2 + (10 × 4) + 1
= 43

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13-7

B) FORMat:ELEMents
Parameters

READing
UNITs
TIME
STATus
VSOurce
ALL
DEFault

= Current or ohms reading
= Units
= Timestamp
= Status information
= Voltage source value
= All data elements
= All except VSOurce

The specified elements are included in the data string in response to :FETCh?, :READ?,
:MEASure?, and :TRACe:DATA?. Note that each element in the item list must be separated by a comma (i.e. send “:ELEMents READing, UNITs, TIME”) to include the reading with units and the time elements in the data string. The elements for the ASCii, ALL
format in the order sent are shown in Figure 13-1. Note that elements are delimited with
commas.
Reading — Returns the current reading for the current function or the ohms readings if
ohms is enabled. An overflow reading is returned as +9.9E37. When a specified data element has invalid data associated with it, NAN (Not A Number) will be the response. NAN
is returned as +9.91E37. -9.9e+36 will be returned for any ohms reading taken when the
voltage source was in compliance.
Units — Units reference the returned readings units of measure. For the current function,
“A” will be returned. For the ohms function, “OHMS” will be returned.
Voltage source — This element returns the programmed voltage source value in volts
when the voltage source is in operate. Zero will be returned when the voltage source output is off. -999 will be returned if the voltage source was in compliance.
Timestamp — Timestamp references the returned data string to a point in time. The
timestamp operates as a timer that starts at zero seconds when the instrument is turned on
or when the timestamp is reset (SYSTem:TIME:RESet). After 99,999.99 seconds, the
timer resets to zero and starts over.
For buffer readings, timestamp can be referenced to the first reading stored in the buffer
(absolute format) which is timestamped at 0 seconds or to the time between each stored
reading (delta format). The TRACe:TSTamp:FORMat command is used to select the
timestamp format.
Status — The status word provides information about Model 6487 operation. The 16-bit
status word is sent in decimal form. The decimal value has to be converted to the binary
equivalent to determine the state of each bit in the word. For example, if the returned status
value is 9, the binary equivalent is 00000001001. Bits 0 and 3 are set. The bits are
explained as follows:
Bit 0 (OFLO) — Set to 1 if measurement performed while in over-range (overflowed
reading).
Bit 1 (Filter) — Set to 1 when measurement performed with the averaging filter enabled.

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Model 6487 Reference Manual

Bit 2 (Math) — Set to 1 when measurement performed with CALC1 enabled.
Bit 3 (Null) — Set to 1 if null for CALC2 is enabled.
Bit 4 (Limits) — Set to 1 if a limit test (CALC2) is enabled.
Bits 5 and 6 (Limit Results) — Provides limit test results:
Bit 6

Bit 5

All limit tests passed

CALC2:LIM1 test failed

CALC2:LIM2 test failed

Bit 7 (Overvoltage) — Set to 1 if measurement performed with an overvoltage condition
on the input.
Bit 9 (Zero Check) — Set to 1 when zero check is enabled.
Bit 10 (Zero Correct) — Set to 1 when zero correct is enabled.
Example — The ASCII data string on page 13-5 contains all four data elements. The status value of 138 has a binary equivalent of 01001010, which indicates that bits B1, B3, and
B7 are set. Therefore, the reading is 1.04056µA with null (REL) and the AVG filter
enabled. The reading was taken 223.6299 seconds after the instrument was turned on. The
voltage source was on and set to +123.45V.

C) FORMat:BORDer
Parameters

NORMal = Normal byte order for IEEE-754 binary format
SWAPped = Reverse byte order for IEEE-754 binary format

For normal byte order, the data format for each element is sent as follows:
Byte 1

Byte 2

Byte 3

Byte 4

For reverse byte order, data is sent as follows:
Byte 4

Byte 3

Byte 2

Byte 1

The “#0” header is not affected by this command. The header is always sent at the beginning of the data string for each measurement conversion.
The ASCII data format can only be sent in the normal byte order. The SWAPped selection
is ignored when the ASCII format is selected.
klqb

The SWAPped byte order must be used when transmitting binary data to any
IBM PC.

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DISPlay, FORMat, and SYSTem

13-9

SYSTem subsystem
Table 13-3
SCPI commands — system
Command
:SYSTem
:ZCHeck
[:STATe]
[:STATe?
:ZCORrect
[:STATe]
[:STATe?]
:ACQuire
:PRESet
:LFRequency
:LFRequency?
:AUTO
[:STATe]
[:STATe]?
:AZERo
[:STATe]
[:STATe]?
:TIME
:RESet
:POSetup
:POSetup?
:VERSion?
:ERRor
[:NEXT]?
:ALL?
:COUNt?
:CODE
[:NEXT]?
:ALL?

Description
Zero check:
Enable or disable zero check.
Query zero check state.
Zero correct:
Enable or disable zero correct.
Query zero correct state.
Acquire a new zero correct value.1
Return to SYSTem:PRESet defaults.
Select power line frequency: 50 or 60 (Hz).
Query power line frequency
Path to control auto line frequency selection.
Turn automatic line frequency ON or OFF.
Query automatic line frequency state.
Path to control autozero:
Enable or disable autozero.
Query autozero state.
Timestamp:
Reset timestamp to 0 seconds.
Select power-on setup; RST, PRESet, or SAV0-2
Query power-on setup.
Query SCPI revision level.
Read messages in error queue:
Return and clear oldest error (code and message).
Return and clear all errors (code and message).
Return the number of errors.
Error code numbers only:
Return and clear oldest error (code only).
Return and clear all errors (codes only).

Default

Ref
Section 3

ON
Section 3
OFF

A
Section 1

Section 3
ON

B
C
Note2

D
Section 10

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Model 6487 Reference Manual

Table 13-3 (cont.)
SCPI commands — system
Command
:SYSTem
:CLEar
:KEY
:KEY?

:LOCal
:REMote
:RWLock
:KLOCK

:KLOCK?

Description

Default

Clear messages from error queue.
Simulate key-press.
Query last key pressed.
RS-232 interface:
Take Model 6487 out of remote (RS-232 only).
Equivalent to GTL.
Put Model 6487 in remote (RS-232 only).
Equivalent to REN.
Enable local lockout (RS-232 only).
Equivalent to LLO.
When true, functions the same as local lockout and
prevents LOCAL key from taking unit out of
remote.
Query key lock state.

Ref
Section 10
E

Section 9

OFF

Section 9

1. ZCH:STAT must be ON and ZCOR:STAT must be OFF in order to acquire a new zero correct value.
2. Clearing the error queue - power-up and *CLS clears the error queue. *RST, SYSTem:PRESet, and STATus:PRESet have no effect
on the error queue.

A) SYSTem:PRESet
Returns the instrument to states optimized for front panel operation. SYSTem:PRESet
defaults are listed in the SCPI tables in Section 14.

B) SYSTem:TIME:RESet
Resets the absolute timestamp to 0 seconds. The timestamp also resets when power is
cycled or after the instrument is on for 99,999.99 seconds. The TRACe:TSTamp:FORMat
command is used to select the absolute timestamp. See the Model 6487 User’s Manual for
details.

C) SYSTem:POSetup
Parameters

RST
PRESet
SAVx

Power-up to *RST defaults
Power-up to SYSTem:PRESet defaults
Power-up to setup stored in memory
(x = memory location 0, 1, or 2)

The *RST and SYSTem:DEFaults are listed in the SCPI tables in the Section 14. A setup
is saved in memory using the *SAV command. See Section 11 (Common Commands) for
details.

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DISPlay, FORMat, and SYSTem

13-11

D) SYSTem:VERSion
Read the version of the SCPI standard being used by Model 6487. Example response
message: 1996.0.

SYSTem:KEY

Parameters

1 = CONFIG/LOCAL key
2 = I | Ω key
3 = MATH key
4 = FILT key
5 = ZCHK key
6 = REL key
7 = OPER key
8 = SOURCE up arrow key
9 = ------10 = ------11 = RANGE up arrow key
12 = AUTO key
13 = RANGE down arrow key
14 = ENTER key
15 = Cursor right arrow key
16 = SOURCE down arrow key

17 = MENU key
18 = COMM key
19 = DISP key
20 = TRIG key
21 = LIMIT key
22 = DIGITS key
23 = RATE key
24 = Cursor left arrow key
25 = ------26 = SAVE key
27 = SETUP key
28 = STORE key
29 = RECALL key
30 = AZERO key
31 = DAMP key
32 = EXIT key

This command is used to simulate front panel key presses. For example, send the following command to simulate pressing the “MATH” key: SYSTem:KEY 3. The queue for the
:SYST:KEY? query command can only hold one key-press and this query cannot be used
to determine keys physically pressed from the front panel.
When :SYST:KEY? is sent and Model 6487 is addressed to talk, the key-press code number for the last :SYST:KEY command is sent to the computer. The value is -1 if a
:SYST:KEY command has not been sent since the last time the unit was placed in remote.
Note that sending :SYST:KEY 1 will simulate a press of the CONFIG key, not LOCAL.
To place the instrument in the local state, send the GTL command as described in
Section 9.

SCPI Reference Tables
•

Table 14-1 — CALCulate command summary

•

Table 14-2 — DISPlay command summary

•

Table 14-3 — FORMat command summary

•

Table 14-4 — SENSe command summary

•

Table 14-5 — SOURce command summary

•

Table 14-6 — STATus command summary

•

Table 14-7 — SYSTem command summary

•

Table 14-8 — TRACe command summary

•

Table 14-9 — TRIGger command summary

•

“Calibration commands” — See Appendix F, Table F-1 on page F-2.

14-2

SCPI Reference Tables

Model 6487 Reference Manual

General notes
•

•
•
•
•

•
•

Brackets ([ ]) are used to denote optional character sets. These optional characters
do not have to be included in the program message. Do not use brackets in the program message.
Angle brackets (< >) are used to indicate parameter type. Do not use angle brackets
in the program message.
The Boolean parameter () is used to enable or disable an instrument operation.
1 or ON enables the operation and 0 or OFF disables the operation.
Uppercase characters indicated the short-form version for each command word.
Default parameter — Listed parameters are both the *RST and SYSTem:PRESet
defaults, unless noted otherwise. Parameter notes are located at the end of each
table.
Ref — Refers you to the section (Sec) that provides operation information for that
command or command subsystem.
SCPI — A checkmark (√) indicates that the command and its parameters are SCPI
confirmed. An unmarked command indicates that it is a SCPI command, but does
not conform to the SCPI standard set of commands. It is not a recognized command by the SCPI consortium. SCPI confirmed commands that use one or more
non-SCPI parameters are explained by notes.

Table 14-1
CALCulate command summary
Command
:CALCulate[1]

Description

Default
Ref
parameter Section SCPI

Path to configure and control CALC1 calculations.

:FORMat

Select math format; MXB (mX+b), RECiprocal
(m/X+b), or LOG10.

:FORMat?

Query math format.

:KMATh

Configure math calculations:

:MMFactor

Set “m” for mX+b and m/X+b calculation:
-9.99999e20 to 9.99999e20.

:MMFactor?

Query “m” factor.

:MA1Factor

Set “m” for mX+b and m/X+b calculation
(same as MMFactor).

:MA1Factor?

Query “m” factor (same as MMFactor?).

:MBFactor

Set “b” for mX+b and m/X+b calculation:
-9.99999e20 to 9.99999e20.

:MBFactor?

Query “b” factor.

5
MXB

√
√
√

1.0

0.0

Model 6487 Reference Manual

SCPI Reference Tables

14-3

Table 14-1 (cont.)
CALCulate command summary
Command

Description

Default
Ref
parameter Section SCPI

:CALCulate[1]

:KMATh
:MA0Factor

Set “b” for mX+b and m/X+b calculation
(same as MBFactor).

:MA0Factor?

Query “b” factor (same as MBFactor?).

:MUNits

Specify units for mX+b or m/X+b result:
1 character: A–Z, ‘[‘=Ω, ‘\’=°, ‘]’=%.

:MUNits?

Query units.

1.0

“X”

√

:STATe

Enable or disable CALC1 calculation.

:STATe?

Query state of CALC1 calculation.

√

:DATA?

Return all CALC1 results triggered by INITiate.

√

:LATest?
:CALCulate2

OFF

Return last (latest) reading.
Path to configure and control limit testing
(CALC2):

√
√

:FEED

Select input path for limit testing: CALCulate[1]
or SENSe[1].

:FEED?

Query input path for limit tests.

√

:LIMit[1]

Limit 1 Testing:

√

:UPPer

Set limit: -9.99999e20 to 9.99999e20.

[:DATA]?

Query upper limit.

:SOURce2 or

Specify 4-bit I/O “fail” pattern (0 to 15).

:SOURce2?

Query output pattern value.

[:DATA]

√

Configure upper limit:

[:DATA]

:LOWer

SENS

√

1.0

√
15

(see
note)

√
√

Configure lower limit:
Set limit: -9.99999e20 to 9.99999e20.

[:DATA]?

Query lower limit.

:SOURce2 or

Specify 4-bit I/O “fail” pattern (0 to 15).

SOURce2 parameter values:
= 0 to 15 Decimal format
= #Bxxxx Binary format (each x = 1 or 0)
= #Hx
Hexadecimal format (x = 0 to F)
= #Qxx Octal format (x = 0 to 17)

√

-1.0

√
15

(see
note)

√

14-4

SCPI Reference Tables

Model 6487 Reference Manual

Table 14-1 (cont.)
CALCulate command summary
Command
:SOURce2?

Description

Default
Ref
parameter Section SCPI
√

Query output pattern value.

:STATe

Enable or disable limit 1 test.

:STATe?

Query state of limit 1 test.

:FAIL?

Return result of limit 1 test: 0 (pass) or 1 (fail).

√
√

:CALCulate2
:LIMit2
:UPPer

8
√

Limit 2 Testing:

√

Configure upper limit:

[:DATA]

Set limit: -9.99999e20 to 9.99999e20.

[:DATA]?

Query upper limit.

:SOURce2 or

Specify 4-bit I/O “fail” pattern (0 to 15).

:SOURce2?

Query output pattern value.

:LOWer

√

OFF

√

1.0

√
15

(see
note)

√
√

Configure lower limit:

[:DATA]

Set limit; -9.99999e20 to 9.99999e20.

[:DATA]?

Query lower limit.

:SOURce2 or

Specify 4-bit I/O “fail” pattern (0 to 15).

:SOURce2?

Query output pattern value.

√

-1.0

√
15

(see
note)

√
√

Enable or disable limit 2 test.

:STATe?

Query state of limit 2 test.

√

Return result of limit 2 test: 0 (pass) or 1 (fail).

√

:FAIL?
:CLIMits
:CLEar
[:IMMEDIATE]
:AUTO
:AUTO?
:PASS

OFF

√

:STATe

Composite limits:
Clear I/O port and restore it back to
SOURce2:TTL settings.
Clear I/O port immediately.
When enabled, I/O port clears when INITiate
is sent.
Query auto-clear state.
Define “pass” Digital I/O output pattern:

SOURce2 parameter values:
= 0 to 15 Decimal format
= #Bxxxx Binary format (each x = 1 or 0)
= #Hx
Hexadecimal format (x = 0 to F)
= #Qxx Octal format (x = 0 to 17)

Model 6487 Reference Manual

SCPI Reference Tables

14-5

Table 14-1 (cont.)
CALCulate command summary
Command

Description

:SOURce2 or

Set 4-bit “pass” pattern.

:SOURce2?

Query output bit pattern.

:DATA?
:LATest?
:NULL
:ACQuire
:OFFSet

(see
note)
√

Return all CALC2 readings triggered by INITiate.
Return only the last (latest) reading.
Configure and control Rel:

√

Use input signal as Rel value.
Specify Rel value: -9.999999e20 to
9.999999e20.

:OFFSet?

Query Rel value.

:STATe

Enable or disable Rel.

:STATe?

Query state of Rel.

:CALCulate3

Default
Ref
parameter Section SCPI

√

0.0

√
√

OFF

√

Path to configure and control CALC3 calculations
on buffer data:

√

:FORMat

Select buffer statistic; MEAN, SDEViation,
MAXimum, MINimum or PKPK.

:FORMat?

Query selected statistic.

√

:DATA?

Read the selected buffer statistic.

√

SOURce2 parameter values:
= 0 to 15 Decimal format
= #Bxxxx Binary format (each x = 1 or 0)
= #Hx
Hexadecimal format (x = 0 to F)
= #Qxx Octal format (x = 0 to 17)

MEAN

√

14-6

SCPI Reference Tables

Model 6487 Reference Manual

Table 14-2
DISPlay command summary
Command

Description

Default
Ref
parameter Section SCPI

:DISPlay

:DIGits

Set display resolution: 4 to 7.

:DIGits?

Query display resolution.

:ENABle

Turn front panel display on or off.

:ENABle?

Query display state.

√

[:WINDow[1]]

Path to control user text messages:

√

:TEXT
[:DATA]

6
(Note 1)

(Note 2)

Read text message.

:STATe

Enable or disable text message mode.

:STATe?

Query state of text message mode.

√

√
√

Define ASCII message “a” (up to 12
characters).

[:DATA]?

√
(Note 3)

√
√

Notes:
1. *RST and SYSTem:PRESet have no effect on the display circuitry. Pressing LOCAL or cycling power enables (ON) the display
circuit.
2. *RST and SYSTem:PRESet have no effect on a user-defined message. Pressing LOCAL or cycling power cancels all user-defined
messages.
3. *RST and SYSTem:PRESet have no effect on the state of the message mode. Pressing LOCAL or cycling power disables (OFF)
the message mode.

Model 6487 Reference Manual

SCPI Reference Tables

14-7

Table 14-3
FORMat command summary
Command

Description

Default
Ref
parameter Section SCPI

:FORMat

[:DATA]
[,]

Specify data format; ASCii, REAL, 32, or
SREal.

[:DATA]?

Query data format.

:ELEMents

Specify data elements; READing, UNITs,
All except
VSOurce, TIME, STATus, DEFault, and ALL.
VSO

:ELEMents?

Query data format elements.

:BORDer

Specify byte order; NORMal or SWAPped.

:BORDer?

Query byte order.

:SREGister

Select data format for reading status registers;
ASCii, HEXadecimal, OCTal, or BINary.

:SREGister?

Query format for reading event registers.

:SOURce2
:SOURce2?

Select data format for reading output patterns:
ASCii, HEXadecimal, OCTal, or BINary.

√

ASC

√

(see Note)

√
ASC

ASC

Query data format for output patterns.

Note: *RST default is NORMal. SYSTem:PRESet default is SWAPped.

Table 14-4
SENSe command summary
Command

Description

Default
Ref.
parameter Section SCPI

[:SENSe[1]]
[:FUNCtion][:]

Select measure function:
= ‘CURRent[:DC]’

:DATA

Path to return instrument readings:

[:LATest]?
[:CURRent[:DC]]
:NPLCycles
:NPLCycles?

‘CURR’

√

Return the last instrument reading.

√

Path to configure amps function:
Set integration rate in line cycles (PLC):
0.01 to 60.0 (60 Hz) or 50.0 (50Hz).
Query NPLC.

√

6 (60Hz)
5 (50Hz)

√
√

14-8

SCPI Reference Tables

Model 6487 Reference Manual

Table 14-4 (cont.)
SENSe command summary
Command

Description

Default
Ref.
parameter Section SCPI

[:SENSe[1]]
[:CURRent[:DC]]
:RANGe

Configure measurement range:

[:UPPer]

Select range: -0.021 to 0.021 (amps).

[:UPPer]?

Query range value.

:AUTO

Enable or disable autorange.

:AUTO?

Query state of autorange.

:ULIMit

Select autorange upper limit: -0.021 to
0.021 (amps).

:ULIMit?

Query upper limit for autorange.

:LLIMit

Select autorange lower limit: -0.021 to
0.021 (amps).

:LLIMit?

Query lower limit for autorange.

:AVERage

Select filter control: MOVing or REPeat.

:TCONtrol?

Query filter control.

:COUNt

Specify filter count: 2 to 100.

:COUNt?

Query filter count.

[:STATe]

Enable or disable digital filter.

[:STATe]?

Query state of digital filter.
Specify “n” for rank: 1 to 5 (rank = 2n+1).

:RANK?

Query rank.

[:STATe]

Enable or disable median filter.

[:STATe]?

Query state of median filter.

:DAMPing

√
√
2.1e-2

2.1e-9

4
MOV
10
OFF
4
1
OFF

Path to control analog filter damping:

[:STATe]

Enable or disable analog filter damping.

[:STATe]?

Query filter damping state.

[:SENSe[1]]
Note: *RST default is ON and SYSTem:PRESet default is OFF.

√

(see Note)

Path to control median filter:

:RANK

√
√

2.1e-4

Path to control the Digital Filter:

:TCONtrol

:MEDian

4
ON

Model 6487 Reference Manual

SCPI Reference Tables

14-9

Table 14-4 (cont.)
SENSe command summary
Command

Description

Default
Ref.
parameter Section SCPI

[:DAMPing]
:OHMS

Path to control ohms:

[:STATe]

Enable or disable ohms for SENSe1 data.

[:STATe]?

Query ohms SENSe1 data state.

:AVOLtage

Path to A-V ohms commands:

[:ARM]

Arm A-V ohms mode.

[:ARM]?

Query if A-V ohms is armed.
(1 = armed).

:ABORt

Abort A-V ohms mode.

:VOLTage

Set high voltage value (-505 to 505V).

:VOLTage?

Query high voltage value.

:TIME

Set time interval for each phase.

:TIME?

3
OFF
3

10V
15s*

Query time interval for each phase.

:POINts?

Query number of points.

:ONEShot

Enable or disable one-shot mode.

:ONEShot?

Query state of one-shot mode.

:CYCLes

Set number of A-V cycles (1 to 9999).

:CYCLes?

Query number of A-V cycles.

:UNITs

Select AMPS or OHMS units.

:UNITs?

Query units.

:CLEar

Clear A-V ohms buffer.

:AUTO

Enable/disable A-V buffer auto clear.

:AUTO?

Query auto clear state.

:BCOunt?

Query number of A-V cycles that have
been completed and are averaged to make
up present buffer.

*15s for 1 PLC or greater, 1s for 0.1 PLC, and 0.1s for 0.02 PLC.

ON
3
AMPS

14-10

SCPI Reference Tables

Model 6487 Reference Manual

Table 14-5
SOURce command summary
Command
:SOURce[1]
:VOLTage
[:LEVel]
[:IMMediate]

Set voltage source amplitude (-500 to
500).1

[:AMPLitude]?

Query voltage source amplitude.

:RANGe

Set source range (10, 50, or 500[V]).

:ILIMit

Set source current limit (2.5e-5 to 2.5e-2[A]).3

:STATe

Enable or disable source output.

:STATe?

Query source output state.

:INTerlock

Path to control interlock:

[:STATe]?
:FAIL?

2.
3.

4.
5.

6.
7.

SOURce1 subsystem:
Path to voltage source commands.

[:AMPLitude]

[:STATe]

Default
Ref.
parameter Section SCPI

Description

Enable or disable interlock for 10V range.5
Query interlock

102
2.5e-2
OFF

OFF

state.6

Query interlock status (1 = interlock
asserted).7

If voltage source is in operate, value will be updated immediately. Value cannot be set above voltage source range.
Default for DDC mode (see Appendix C) is 50V.
Limit settings are: 25μA, 250μA, 2.5mA, and 25mA; current limit will be set to closest programmed value. For the 500V and the
50V ranges, the maximum ILIMit is 2.5mA (0.0025A). On the 10V range, any of the four current limit choices can be selected.
The default 10V Ilimit is 25mA or 2.5mA in DDC mode (see Appendix C).
STATe ON places source in operate.
Ignored for 50V and 500V ranges since interlock is always enabled. Attempting to turn off the interlock state while on the 50 or
500V range will generate a “-221 Settings Conflict” error. Upranging from the 10V range will always cause the interlock to be
enabled. When the unit returns to the 10V range, the interlock state will be reset to the state it had when the unit left the 10V range.
Querying the interlock state while on the 50V or 500V range will always return TRUE.
Asserted interlock indicates that voltage source cannot be placed in operate.

Model 6487 Reference Manual

SCPI Reference Tables

14-11

Table 14-5 (cont.)
SOURce command summary
Command

Description

Default
Ref.
parameter Section SCPI

:SOURce[1]
:VOLTage
:SWEep

Sweep commands:

:STARt

Program start voltage: -505V to 505V.

:STARt?

Query start voltage.

:STOP

Program stop voltage: -505V to 505V.

:STOP?

Query stop voltage.

:STEP

Program step voltage: -505V to 505V.

:STEP?

Query step voltage.

:CENTer

Program center voltage: -505V to 505V.

:CENTer?

Query center voltage.

:SPAN

Program span voltage: -505V to 505V.

:SPAN?

Query span voltage.

:DELay

Set delay: 0 to 999.9999s.

:DELay?

Query delay.

:INITiate

Arm sweep, put source in operate.

:ABORt

Abort sweep, put source in standby.

:STATe?

Query if sweep running: 1 = sweep in
progress.

:SOURce2
:TTL

0V
10V
1V
5V
10V
1s

Path to control Digital I/O port:

Set I/O port value directly:

[:LEVel] or

Specify 4-bit Digital I/O pattern (0 to 15).

[:LEVel]?

Query output value.

:CLEar

Clear I/O port (return output to TTL value).

[:IMMediate]

Clear I/O port immediately.

:AUTO

Enable or disable auto-clear.

SOURce2 parameter values:
= 0 to 15 Decimal format
= #Bxxxx Binary format (each x = 1 or 0)
= #Hx
Hexadecimal format (x = 0 to F)
= #Qxx Octal format (x = 0 to 17)

OFF

(see
note)

14-12

SCPI Reference Tables

Model 6487 Reference Manual

Table 14-5 (cont.)
SOURce command summary
Command
:AUTO?

Description
Query auto-clear state.

:DELay

Specify delay (pulse width) for pass/fail
pattern: 0 to 60 (sec).

:DELay?

Query delay value.

:TTL4

Default
Ref.
parameter Section SCPI
0.0001

Line 4 mode configuration:

:MODE

Select output line 4 mode: EOTest or BUSY.

:MODE?

Query line 4 mode.

:BSTate

Select active TTL level for busy: 1 = ON
or 0 = OFF.

:BSTATe?

Query active busy TTL level.

EOT
0

Model 6487 Reference Manual

SCPI Reference Tables

14-13

Table 14-6
STATus command summary
Command

Description

:STATus
:MEASurement

Default
Ref
parameter Section SCPI
(Note 1)

√

Measurement event registers:

[:EVENt]?

Read the event register.

(Note 2)

:ENABle or

Program the enable register.

(Note 3)

:ENABle?

Read the enable register.

:CONDition?

Read the condition register.

:STATus

10
√

:OPERation

Operation event registers:

[:EVENt]?

Read the event register.

(Note 2)

√

:ENABle or

Program the enable register.

(Note 3)

√

:ENABle?

Read the enable register.

√

:CONDition?

Read the condition register.

√

:QUEStionable

Questionable event registers:

√

[:EVENt]?
:ENABle or

Read the event register.

(Note 2)

√

Program the enable register.

(Note 3)

√

:ENABle?

Read the enable register.

√

:CONDition?

Read the condition register.

√

:PRESet

Return status registers to default states.

:QUEue

Read error queue:

√
√

[:NEXT]?

Read and clear oldest error/status (code and
message).

(Note 4)

√

:ENABle

Specify error and status messages for error
queue.

(Note 5)

√

:ENABle?

Read the enabled messages.

Notes:
1. Commands in this subsystem are not affected by *RST or SYSTem:PRESet. The effects of cycling power, *CLS and
STATus:PRESet are explained by the following notes.
2. Event registers — Power-up and *CLS clears all bits. STATus:PRESet has no effect.
3. Enable registers — Power-up and STATus:PRESet clears all bits. *CLS has no effect.
4. Error queue — Power-up and *CLS empties the error queue. STATus:PRESet has no effect.
5. Error queue messages — Power-up enables error messages and disables status messages. *CLS and STATus:PRESet have no
effect.

√

14-14

SCPI Reference Tables

Model 6487 Reference Manual

Table 14-6 (cont.)
STATus command summary
Command

Description

:DISable

Specify messages not to be placed in queue.

:DISable?

Read the disabled messages.

:CLEar

Clear messages from error queue.

Default
Ref
parameter Section SCPI
(Note 5)

Parameters:

=
=
=
=
=

#Bxx…x
#Hx
#Qx
0 to 65535
(100:200, -224)

Binary format (each x = 1 or 0)
Hexadecimal format (x = 0 to FFFF)
Octal format (x = 0 to 177777)
Decimal format
Example of a range and single entry (+100 through +200 and -224).

Notes:
1. Commands in this subsystem are not affected by *RST or SYSTem:PRESet. The effects of cycling power, *CLS, and
STATus:PRESet are explained by the following notes.
2. Event registers — Power-up and *CLS clears all bits. STATus:PRESet has no effect.
3. Enable registers — Power-up and STATus:PRESet clears all bits. *CLS has no effect.
4. Error queue — Power-up and *CLS empties the error queue. STATus:PRESet has no effect.
5. Error queue messages — Power-up enables error messages and disables status messages. *CLS and STATus:PRESet have no
effect.

Model 6487 Reference Manual

SCPI Reference Tables

14-15

Table 14-7
SYSTem command summary (see Section 13 for detailed information)
Command

Description

Default
Ref
parameter Section SCPI

:SYSTem
:ZCHeck

13
Zero check:

[:STATe]

Enable or disable zero check.

[:STATe]?

Query state of zero check.

:ZCORrect

Enable or disable zero correct.

[:STATe]?

Query state of zero correct.

:ACQuire

Acquire a new zero correct value. *

:PRESet

Return to SYSTem:PRESet defaults.

:LFRequency

Select power line frequency: 50 or 60 (Hz).

:LFRequency?

Query frequency setting.
Enable or disable auto frequency.

[:STATe]?

Query state of auto frequency.
Enable or disable autozero.

[:STATe]?

Query state of autozero.

:RESet

OFF

√
60

Path to control autozero:

[:STATe]
:TIME

Path to control auto frequency.

[:STATe]
:AZERo

Zero correct:

[:STATe]

:AUTO

√
√

√

Timestamp:
Reset timestamp to 0 seconds.

:POSetup

Select power-on setup: RST, PRESet, or SAVx
(where x = 0 – 2).

:POSetup?

Query power-on setup.

:VERSion?

Query SCPI revision level.

:ERRor

Read error queue:

[:NEXT]?

Read and clear oldest error/status (code and
message).

:ALL?

Read and clear all errors/status (code and
message).

PRES

√
(see note)

√

* ZCH:STAT must be ON and ZCOR:STAT must be OFF in order to acquire a new zero correct value.
Note: Clearing the error queue – Power-up and *CLS clears the error queue. *RST, SYSTem:PRESet, and STATus:PRESet have no
effect on the error queue.

14-16

SCPI Reference Tables

Model 6487 Reference Manual

Table 14-7 (cont.)
SYSTem command summary (see Section 13 for detailed information)
Command

Description

:COUNt?

Read the number of messages in queue.

:CODE

Code numbers only:

[:NEXT]?

Read and clear oldest error/status (code
only).

:ALL?

Read and clear all errors/status (codes only).

Default
Ref
parameter Section SCPI

:SYSTem:
:CLEar

Clear messages from error queue.

:KEY

Simulate key-press.

√

:KEY?

Query the last “pressed” key.

√

RS-232 interface:
:LOCal

While in LLO, removes the LLO and places the
Model 6487 in local (RS-232 only).

:REMote

Places the Model 6487 in remote if not in LLO
(RS-232 only).

:RWLock

Places the Model 6487 in local lockout (RS-232
only).

:KLOCK

When true, functions the same as local lockout
and prevents LOCAL key from taking unit out
of remote.

:KLOCK?

Query key lock state.

OFF

Model 6487 Reference Manual

SCPI Reference Tables

14-17

Table 14-8
TRACe command summary
Command
:TRACe|:DATA

Use :TRACe or :DATA as root command.

:DATA? [BUFFER]

Read the contents of normal or A-V ohms
buffer.2

:MODE?

Query buffer mode:
DC (normal) or AVOLtage (A-V ohms).

:CLEar

Clear readings from buffer.

:FREE?

Query bytes available and bytes in use.

:POINts

Specify size of buffer: 1 to 3000.

:ACTual?

Description

Default
Ref
parameter Section SCPI
Note1

BUFFER

√
√

√
100

√

Query number of readings stored in buffer.

:POINts?

Query buffer size.

:FEED

Select source of readings for buffer: SENSe[1],
CALCulate[1], or CALCulate2.

:CONTrol

Select buffer control mode: NEXT or NEVer.

:CONTrol?

Query buffer control mode.

:FEED?

Query source of readings for buffer.

:TSTamp

Timestamp:

:FORMat

Select timestamp format: ABSolute or DELta.

:FORMat?

Query timestamp format.

√
SENS1

√

NEV

√
√
√

ABS

SYSTem:PRESet and *RST have no effect on the commands in this subsystem. The listed defaults are power-on defaults.
Readings come from A-V ohms buffer if available; normal buffer readings otherwise.

14-18

SCPI Reference Tables

Model 6487 Reference Manual

Table 14-9
TRIGger command summary
Command
:INITiate
[:IMMediate]

Description

Default
Ref
parameter Section SCPI

Path to initiate measurement cycle(s):

√
√

Initiate one trigger cycle.

:ABORt

Reset trigger system (goes to idle state).

√

:ARM[:SEQuence[1]]

Path to configure arm layer:

√

[:LAYer[1]]
:SOURce

Select control source: IMMediate, TIMer,
BUS, TLINk, MANual, PSTest, NSTest, or
BSTest.

:SOURce?

Query arm control source.

:COUNt

Set measure count: 1 to 2048 or INF (infinite).

:COUNt?

Query measure count.

:TIMer

Set timer interval: 0.001 to 99999.999 (sec).

:TIMer?

Query timer interval.

IMM

√
1

√
√

0.100

√
√
√

[:TCONfigure]

√

:DIRection

Enable (SOURce) or disable (ACCeptor)
bypass.

:DIRection?

Query arm source bypass.

[:ASYNchronous]

Configure input/output triggers:

:ILINe

Select input trigger line: 1, 2, 3, 4, 5, or 6.

:ILINe?

Query input trigger line.

:OLINe

Select output trigger line: 1, 2, 3, 4, 5, or 6.

:OLINe?

Query output trigger line.

:OUTPut

Output trigger (TRIGger) or not at all
(NONE).

:OUTPut?

Query output trigger status.

*RST default is 1. SYST:PRES default is INF.

ACC

√
√

1
2
NONE

Model 6487 Reference Manual

SCPI Reference Tables

14-19

Table 14-9 (cont.)
TRIGger command summary
Command
:TRIGger

Description
Trigger layer:

:CLEar

Clear pending input trigger immediately.

[:SEQuence[1]]

Trigger path.

:SOURce

Select control source: IMMediate or TLINk.

:SOURce?

Query trigger control source.

:COUNt

Set measure count: 1 to 2048 or INF (infinite).

:COUNt?

Query measure count.

:DELay

Set trigger delay: 0 to 999.9999 (sec).

:AUTO

Enable or disable auto delay.

:AUTO?

Query state of auto delay.

:DELay?

Default
Ref
parameter Section SCPI
7

IMM

√

√
√

0.0

√

OFF

√
√
√

Query delay value.

√

[:TCONfigure]
:DIRection

Enable (SOURce) or disable (ACCeptor)
bypass.

:DIRection?

Query trigger source bypass.

[:ASYNchronous]

Configure input/output triggers:

:ILINe

Select input trigger line; 1, 2, 3, 4, 5, or 6.

:ILINe?

Query input trigger line.

:OLINe

Select output trigger line; 1, 2, 3, 4, 5, or 6.

:OLINe?

Query output trigger line.

:OUTPut

Output trigger after measurement (SENSe)
or not at all (NONE).

:OUTPut?

Query output trigger status.

ACC

√
√

1
2
NONE

Performance Verification
•

Verification test requirements — Summarizes environmental conditions, warmup period, and line power requirements.

•

Recommended test equipment — Lists all equipment necessary for verification
and gives pertinent specifications.

•

Verification limits — Describes how reading limits are calculated and gives an
example.

•

Calibrator voltage calculations — Details the method for calculating calibrator
voltages when testing the 2nA to 2μA ranges.

•

Performing the verification test procedures — Summarizes test considerations
and describes how to restore factory defaults.

•

Offset voltage calibration — Lists steps necessary to null voltage offset before
performing verification.

•

Current measurement accuracy — Lists detailed steps for verifying measurement accuracy of all current ranges. The 2nA to 2μA and 20μA to 20mA ranges
are covered separately because of the different test equipment required.

•

Voltage source output accuracy — Summarizes the method to test voltage source
output accuracy.

15-2

Performance Verification

Model 6487 Reference Manual

Introduction
Use the procedures in this section to verify that Model 6487 accuracy is within the limits
stated in the instrument’s one-year accuracy specifications. You can perform these verification procedures:
•
•
•
•

When you first receive the instrument to make sure that it was not damaged during
shipment.
To verify that the unit meets factory specifications.
To determine if calibration is required.
Following calibration to make sure it was performed properly.

t^okfkd

klqb

The information in this section is intended only for qualified service
personnel. Do not attempt these procedures unless you are qualified to
do so. Some of these procedures may expose you to hazardous voltages,
which could cause personal injury or death if contacted. Use standard
safety precautions when working with hazardous voltages.

If the instrument is still under warranty and its performance is outside specified
limits, contact your Keithley representative or the factory to determine the correct course of action. Refer to Section 16 for calibration procedures.

Verification test requirements
Be sure that you perform the verification tests:
•
•
•
•
•

Under the proper environmental conditions.
After the specified warm-up period.
Using the correct line voltage.
Using the proper test equipment.
Using the specified test signals and reading limits.

Environmental conditions
Conduct your performance verification procedures in a test environment with:
•
•

An ambient temperature of 65° to 82°F (18° to 28°C).
A relative humidity of less than 70% unless otherwise noted.

Model 6487 Reference Manual

Performance Verification

15-3

Warm-up period
Allow the Model 6487 to warm up for at least one hour before conducting the verification
procedures. If the instrument has been subjected to temperature extremes (those outside
the ranges stated above), allow additional time for the instrument’s internal temperature to
stabilize. Typically, allow one extra hour to stabilize a unit that is 18°F (10°C) outside the
specified temperature range.
Allow the test equipment to warm up for the minimum time specified by the manufacturer.

Line power
The Model 6487 requires a line voltage of 100 to 120V or 220 to 240V at a line frequency
of 50 to 60Hz. Verification tests must be performed within this range. Be sure the line voltage setting agrees with the expected line voltage (Section 17).

Recommended test equipment
Table 15-1 summarizes recommended verification equipment. You can use alternate
equipment, but keep in mind that test equipment accuracy will add to the uncertainty of
each measurement. Generally, the test equipment should have accuracy or uncertainty at
least four times better than corresponding Model 6487 specifications. Note, however, that
the recommended calibrator listed in Table 15-1 does not meet this requirement for 20μA
output. See Table 16-2 and Table 16-3 in Section 16 for details on uncertainty ratios.

15-4

Performance Verification

Model 6487 Reference Manual

Table 15-1
Recommended performance verification equipment
Description
Calibrator

Manufacturer/Model
Fluke 5700A

Specifications
DC Voltage:1
2V: 7ppm
20V: 5ppm
200V: 7ppm
DC Current:1
20μA: 550ppm
200μA: 100ppm
2mA: 55ppm
20mA: 55ppm

Electrometer Calibration
Standard

Keithley Model 5156

Nominal Resistance:2
100MΩ: 200ppm
1GΩ: 300ppm

Digital Multimeter

Keithley Model 2001

DC Voltage:3
10V: 32ppm
50V: 50ppm
500V: 53ppm

Low-noise triax cable
Low-noise coax cable
Triax shielding cap
Triax-to-BNC adapter
Dual banana-to-BNC adapter
Banana plug test leads

Keithley 7078-TRX-3
Keithley 4801
Keithley CAP-31
Keithley 7078-TRX-BNC
Pomona 1269
Keithley 8607

1.
2.
3.

90-day, 23°±5°C full-range accuracy specifications shown. Uncertainty for 20μA output current does not meet the recommended
four-times better uncertainty specification.
23°±3°C accuracy of characterization.
One-year, DMM accuracy specifications at specified voltage and range.

Model 6487 Reference Manual

Performance Verification

15-5

Verification limits
The verification limits stated in this section have been calculated using only Model 6487
one-year accuracy specifications and they do not include test equipment uncertainty. If a
particular measurement falls outside the allowable range, recalculate new limits based on
both Model 6487 specifications and corresponding test equipment specifications.

Example reading limits calculation
As an example of how verification limits are calculated, assume you are testing the 20mA
range using a 20mA input value. Using the Model 6487 20mA range accuracy specification of ±(0.1% of reading + 1μA), the calculated reading limits are:
Reading limits = 20mA ± [(20mA × 0.1%) + 1μA]
= 20mA ± (0.02mA + 0.001mA)
= 20mA ± 0.021mA
= 19.979mA to 20.021mA

Calibrator voltage calculations
When verifying the 2nA-2μA current ranges, you must calculate the actual calibrator voltages from the desired current values and the characterized Model 5156 Calibration
Standard resistor values.
Calibrator voltages required for verification currents are calculated as follows:
Where:

V = IR
V = required calibrator voltage
I = verification current
R = actual standard resistor value

For example, assume you are testing the 20nA range using an actual 100.5MΩ standard
resistor value. The actual calibrator voltage is: 20nA × 100.5MΩ = 2.01V.

15-6

Performance Verification

Model 6487 Reference Manual

Performing the verification test procedures
Test considerations
When performing the verification procedures:
•
•
•
•
•

Be sure to restore Model 6487 factory front panel defaults and perform voltage offset calibration as outlined below.
Make sure that the test equipment is properly warmed up and properly connected to
the correct Model 6487 terminal(s).
Be sure the test equipment is set up for the proper function and range.
Allow the input signal to settle before making a measurement.
Do not connect test equipment to the Model 6487 through a scanner, multiplexer,
or other switching equipment.

t^okfkd

The maximum safe voltage between the voltage source or ammeter and
chassis ground (common mode voltage) is 505V DC. Exceeding this
voltage can create a shock hazard.

`^rqflk

Maximum continuous input voltage is 505V DC. Exceeding this value
may cause instrument damage.

Restoring factory defaults
Before performing the verification procedure, restore the instrument to its factory front
panel defaults as follows:
1.
2.
klqb

Press SETUP. The instrument will display the following prompt:
RESTORE: FACT
Using either RANGE key, select FACT then restore the factory default conditions
by pressing ENTER.
You can use either RANGE key to select among FACT, GPIB, and USR0 to USR2
setups. Be sure you use FACT defaults for the verification procedure.

Model 6487 Reference Manual

Performance Verification

15-7

Offset voltage calibration
Before performing the current performance verification procedure, perform offset voltage
calibration as outlined below.
1.
2.
3.
4.
5.
6.

Press the MENU key, select CAL, then press ENTER.
The unit will display the following:
CAL: VOFFSET
Press ENTER. The instrument will prompt as follows:
INPUT CAP
Connect the triax shielding cap to the INPUT jack.
Press ENTER to complete offset voltage calibration.
Press EXIT to return to normal display.

Current measurement accuracy
Follow the steps below to verify that Model 6487 current measurement accuracy is within
specified limits. The test involves applying accurate DC currents and then verifying that
the Model 6487 current readings are within required limits.

20µA-20mA range accuracy
1.

2.
3.
4.
5.
6.
7.

With the power off, connect the current calibrator to the Model 6487 INPUT jack
(Figure 15-1). Use the appropriate coax cable, triax-to BNC adapter, and BNC-todual banana plug adapter where shown.
Turn on the Model 6487 and calibrator. Allow them to warm up for one hour.
Set the Model 6487 to the 20μA range using the up or down RANGE key.
With zero check enabled, zero correct the Model 6487 and then disable zero check.
Set the calibrator current to 0.0000μA and make sure the output is turned on.
Enable the Model 6487 REL mode. Leave REL enabled for the remainder of the
test.
Verify current measurement accuracy for each of the currents listed in Table 15-2.
For each test point:
• Select the correct Model 6487 measurement range.
• Set the calibrator current to the indicated value.
• Verify that the Model 6487 current reading is within the limits given in the
table.
Repeat the procedure for negative source currents with the same magnitudes as
those listed in Table 15-2.

Performance Verification

Model 6487 Reference Manual

Table 15-2
Reading limits for 20µA to 20mA ranges
Model 6487
Range

Calibrator
Current

Model 6487 Current Reading Limits
(1 Year, 18°C-28°C)

20μA

20.0000μA

19.9790 to 20.0210μA

200μA

200.000μA

199.790 to 200.210μA

2mA

2.00000mA

1.99790 to 2.00210mA

20mA

20.0000mA

19.9790 to 20.0210mA

Figure 15-1
Connections for 20µA to 20mA range verification
Coax Cable
INPUT
MADE IN
U.S.A.

CAT I

IEEE-488

ANALOG OUT

(CHANGE IEEE ADDRESS
WITH FRONT PANEL MENU)

DIGITAL I/O

!
505V PK
505V PK
505V PK
TRIGGER LINK

INPUT

RS-232

V-SOURCE OUTPUT
505V PK TO CHASSIS
LO

HI INTERLOCK
505V
MAX

120

15-8

FUSE

LINE

400mAT
(SB)

100 VAC
120 VAC

200mAT
(SB)

220 VAC
240 VAC

LINE RATING
50, 60Hz
50 VA MAX

Model 6487 Picoammeter
Triax-to-BNC
Adapter

DC Current Calibrator
Dual banana-to-BNC
adapter. Connect
Output LO to shield.

2nA-2µA range accuracy
1.

2.
3.
4.
5.
6.

With the power off, connect the voltage calibrator and Model 5156 Electrometer
Calibration Standard to the Model 6487 INPUT jack (Figure 15-2). Initially, make
connections to the 1GΩ resistor in the calibration standard.
Turn on the Model 6487 and calibrator power. Allow them to warm up for one
hour.
Set the Model 6487 to the 2nA range.
With zero check enabled, zero correct the instrument and then disable zero check.
Set the calibrator voltage to 0.0000V and make sure the output is turned on.
Enable the Model 6487 REL mode. Leave REL enabled for the remainder of the
test.

Model 6487 Reference Manual

Performance Verification

15-9

Verify current measurement accuracy for each of the currents listed in Table 15-3.
For each test point:
• Make connections to the indicated calibration standard resistor.
• Select the correct Model 6487 measurement range.
• Calculate the actual required calibrator voltage: V = IR; where I is the desired
applied current and R is the actual standard resistor value.
• Set the calibrator to the calculated voltage.
• Verify that the Model 6487 current reading is within the reading limits listed in
the table.
Repeat the procedure for negative source currents with the same magnitudes as
those listed in Table 15-3.

Table 15-3
Reading limits for 2nA to 2µA ranges
Model
6487
range

Nominal
calibrator
voltage

Calibration
standard
resistor1

Nominal
applied
current

Actual
voltage2

Model 6487 current
reading limits
(1 Year, 18°C-28°C)

2nA

1GΩ

2.00000nA

______V

1.99160 to 2.00840nA

20nA

100MΩ

20.0000nA

______V

19.9190 to 20.0810nA

200nA

20V

100MΩ

200.000nA

______V

199.590 to 200.410nA

2μA

200V

100MΩ

2.00000μA

______V

1.99690 to 2.00310μA

1.
2.

Nominal resistance values shown. Use actual characterized value for calculations.
Calculate actual calibrator voltage as follows: V = IR; where I is desired applied current and R is actual standard resistance value.

15-10

Performance Verification

Model 6487 Reference Manual

Figure 15-2
Connections for 2nA to 2µA range verification
DC Voltage Calibrator
Model 6487 Picoammeter
BNC-to-dual
Banana Plug
Adapter

MADE IN
U.S.A.

CAT I

IEEE-488

ANALOG OUT

(CHANGE IEEE ADDRESS
WITH FRONT PANEL MENU)

DIGITAL I/O

!
505V PK
505V PK
505V PK

TRIGGER LINK

INPUT

RS-232

V-SOURCE OUTPUT
505V PK TO CHASSIS

HI INTERLOCK
505V
MAX

120

FUSE

LINE

400mAT
(SB)

100 VAC
120 VAC

200mAT
(SB)

220 VAC
240 VAC

LINE RATING
50, 60Hz
50 VA MAX

Connect
Cable
Shield to
Output LO
Low-noise
Coax Cable

INPUT
Triax Cable

10GΩ

100GΩ
OUTPUT
1nF

1GΩ
!

100nF

100MΩ

Note: Connect Calibrator to
100MΩ or 1GΩ Resistor
Link Shield and Chassis

Model 5156 Calibration Standard

Voltage source output accuracy
Follow the steps below to verify that Model 6487 voltage source output accuracy is within
specified limits. The test involves setting the voltage source output to specific values and
then verifying that DMM voltage readings are within required limits.
t^okfkd

2.
3.
4.

Hazardous voltages will be present during the following procedure.
Use care to avoid a shock hazard. The interlock must be closed to test
the 50V and 500V ranges. See Section 2 for interlock information.

With the power off, connect the DMM INPUT terminals to the Model 6487
V-SOURCE OUTPUT jacks (Figure 15-3). Be sure to observe polarity (HI to HI;
LO to LO).
Turn on the DMM and Model 6487; allow them to warm up for one hour.
Select the DMM DCV function and enable autoranging.
Temporarily short the ends of the DMM test leads together, then enable the DMM
REL mode to null offsets. Leave REL enabled for the remainder of the tests.

Model 6487 Reference Manual

Performance Verification

Verify voltage source accuracy for each of the values listed in Table 15-4. For each
test point:
• Select the correct Model 6487 voltage source range.
• Set the voltage source output to the indicated value.
• Make sure the voltage source is in operate (output on).
• Verify that the DMM voltage reading is within the limits given in the table.
Repeat the procedure for negative source currents with the same magnitudes as
those listed in Table 15-4.

Table 15-4
Reading limits for voltage source accuracy
Model 6487
Source Range

Output
Voltage

Model 6487 Output Voltage Limits
(1 Year, 18°C-28°C)

10V

10.000V

9.989 to 10.011V

50V

50.000V

49.946 to 50.054V

500V

500.00V

499.21 to 500.79V

Figure 15-3
Connections for voltage source output accuracy
Model 6487

INPUT

Model 2001 DMM
SENSE
Ω 4 WIRE

INPUT

MADE IN
U.S.A.

CAT I

IEEE-488

ANALOG OUT
350V
PEAK

!
505V PK
505V PK
505V PK

ACV

DCI

ACI

Ω2

Ω4

FREQ

RANGE

TRIGGER LINK

INPUT

500V
PEAK

INPUTS

TEMP

REL

TRIG

STORE RECALL

INFO

LOCAL

CHAN

AUTO

FILTER MATH

SCAN

CONFIG MENU

EXIT

FRONT/REAR

CAL

AMPS

505V
MAX

ENTER

V-SOURCE
OUTPUT

HI INTERLOCK

2A 250V

RANGE

POWER

RS-232

V-SOURCE OUTPUT
505V PK TO CHASSIS

120

LO
DCV

DISPLAY

(CHANGE IEEE ADDRESS
WITH FRONT PANEL MENU)

DIGITAL I/O

1100V
PEAK

2001 MULTIMETER
PREV

15-11

FUSE

LINE

400mAT
(SB)

100 VAC
120 VAC

200mAT
(SB)

220 VAC
240 VAC

LINE RATING
50, 60Hz
50 VA MAX

Calibration
•

Environmental conditions — Summarizes temperature and relative humidity,
warm-up period, and line power requirements.

•

Calibration considerations — Lists considerations to take into account when
calibrating the unit.

•

Calibration cycle — States how often the Model 6487 should be calibrated.

•

Recommended calibration equipment — Lists all equipment necessary for calibration and gives pertinent specifications.

•

Calibration errors — Discusses error messages that might occur during
calibration.

•

Calibration menu — Discusses calibration menu items.

•

Aborting calibration — Describes how to halt the calibration procedure at any
time.

•

Current calculations — Details how to calculate currents from calibrator voltages
and standard resistor values when calibrating the 2nA to 2μA ranges.

•

Calibration procedure — Provides step-by-step procedures for calibrating all current ranges, as well as all three ranges of the voltage source. The 2nA to 2μA and
20μA to 20mA ranges require separate procedures because of the different calibration equipment involved.

•

Calibration support — Describes how to change the calibration code, reset the
calibration code, and view calibration dates and count.

16-2

Calibration

Model 6487 Reference Manual

Introduction
Use the procedures in this section to calibrate the Model 6487 from the front panel. (See
Appendix F for information on remote calibration.) These procedures require accurate test
equipment to source precise DC voltages, currents, and resistances.
t^okfkd

Environmental conditions
Temperature and relative humidity
Conduct the calibration procedures at an ambient temperature of 22° to 24°C with relative
humidity of less than 70% unless otherwise noted.

Warm-up period
Allow the Model 6487 to warm up for at least one hour before performing calibration.
If the instrument has been subjected to temperature extremes (those outside the ranges
stated above), allow additional time for the instrument’s internal temperature to stabilize.
Typically, allow one extra hour to stabilize a unit that is 10°C outside the specified temperature range.
Allow the test equipment to warm up for the minimum time specified by the manufacturer.

Line power
The Model 6487 requires a line voltage of 100 to 120V or 220 to 240V at a line frequency
of 50 to 60Hz. The instrument must be calibrated while operating from a line voltage
within this range. Be sure the line voltage setting agrees with the expected line voltage
(Section 17).

Model 6487 Reference Manual

Calibration

16-3

Calibration considerations
When performing the calibration procedures:
•
•
•
•

Make sure that the test equipment is properly warmed up and connected to the correct Model 6487 terminal(s).
Always allow the source signal to settle before calibrating each point.
Do not connect test equipment to the Model 6487 through a scanner or other
switching equipment.
If an error occurs during calibration, the Model 6487 will generate an appropriate
error message.

t^okfkd

The maximum safe voltage between the voltage source or ammeter and
chassis ground (common mode voltage) is 505V DC. Exceeding this
voltage can create a shock hazard.

`^rqflk

Maximum continuous input voltage is 505V DC. Exceeding this value
may cause instrument damage.

Calibration cycle
Perform verification at least once a year to ensure the unit meets or exceeds its specifications (see Section 15). Calibrate if necessary.

Recommended calibration equipment
Table 16-1 lists the recommended equipment for the calibration procedures. You can use
alternate equipment, but keep in mind that test equipment uncertainty will affect calibration accuracy. Calibration equipment should have accuracy specifications at least four
times better than corresponding Model 6487 specifications. Note, however, that the recommended calibrator listed in Table 16-1 does not meet this requirement for 20μA output.
Table 16-2 lists uncertainty ratios for current calibration equipment, while Table 16-3 lists
uncertainty ratios for voltage source calibration equipment.

16-4

Calibration

Model 6487 Reference Manual

Table 16-1
Recommended calibration equipment
Description
Calibrator

Manufacturer/Model
Fluke 5700A

Specifications
DC Voltage:1
2V: 7ppm
20V: 5ppm
200V: 7ppm
DC Current:1
20μA: 550ppm
200μA: 100ppm
2mA: 55ppm
20mA: 55ppm

Electrometer Calibration
Standard

Keithley Model 5156

Nominal Resistance:2
100MΩ: 200ppm
1GΩ: 300ppm

Digital Multimeter

Keithley Model 2001

DC Voltage:3
10V: 32ppm
50V: 50ppm
500V: 53ppm

Low-noise triax cable
Low-noise coax cable
Triax shielding cap
Triax-to-BNC adapter
Dual banana-to-BNC adapter
Banana plug test leads

Keithley 7078-TRX-3
Keithley 4801
Keithley CAP-31
Keithley 7078-TRX-BNC
Pomona 1269
Keithley 8607

1.
2.
3.

90-day, 23°±5°C full-range accuracy specifications shown. Includes ppm of range and offset. Uncertainty for 20µA output current does not meet the recommended four-times better uncertainty specification.
23°±3°C accuracy of characterization.
One-year, DMM accuracy specifications at specified voltage and range.

Calibration errors
The Model 6487 checks for errors after each calibration step, minimizing the possibility
that improper calibration may occur due to operator error. If an error is detected during
calibration, the instrument will display an appropriate error message. The unit will then
prompt you to repeat the calibration step that caused the error.

Model 6487 Reference Manual

Calibration

16-5

Table 16-2
Current test uncertainty ratios with recommended equipment
Range

5700 + 5156

Test uncertainty
ratio

2nA

7ppm + 300ppm

13.0

20nA

7ppm + 200ppm

19.3

200nA

5ppm + 200ppm

9.8

2μA

7ppm + 200ppm

7.2

20μA

550ppm

1.8

200μA

100ppm

10.0

2mA

55ppm

18.2

20mA

55ppm

18.2

Table 16-3
Voltage source test uncertainty ratios with recommended equipment
Range

2001 DMM

Test uncertainty
ratio

10V

32ppm

31.2

50V

50ppm

20.0

500V

53ppm

28.3

Calibration menu
You can access the calibration menu by pressing MENU, selecting CAL, and then pressing ENTER. The various selections are summarized in Table 16-4. Use the up and down
RANGE keys to scroll through these selections.

16-6

Calibration

Model 6487 Reference Manual

Table 16-4
Calibration menu
Menu Item*

Description

VOFFSET

Performs offset voltage calibration.

COUNT

Displays calibration count.

RUN

Calibrates present current range.

VSRC-RUN

Calibrates present voltage source range.

DATES

Displays calibration and due dates.

UNLOCK

Unlocks calibration using code.

LOCK

Locks cal, exits to the main menu.

SAVE

Saves calibration constants.

* Press MENU, select CAL, then press ENTER to access. Use up or
down RANGE key to scroll through selections.

Aborting calibration
You can abort the calibration procedure at any time by pressing the EXIT key.

Current calculations
When calibrating the 2nA-2μA current ranges, you must calculate the actual current values from the applied calibrator voltages and the characterized Model 5156 Calibration
Standard resistor values. Calibration currents are calculated as follows:
Where:

I = V/R
I = required calibration current
V = calibrator voltage
R = actual standard resistor value

For example, assume you are calibrating the 20nA range using a 2V calibrator voltage
with an actual 100.5MΩ standard resistor value. The actual calibration current is:
2V/100.5MΩ = 19.9005nA.

Model 6487 Reference Manual

Calibration

16-7

Calibration procedure
The calibration procedure should be performed in the following order:
•
•
•
•
•
•

Preparing for calibration
Offset voltage calibration
Current calibration
Voltage source calibration
Entering calibration dates and saving calibration
Locking out calibration

Preparing for calibration
1.
2.

3.
4.
5.

Turn on the Model 6487 and the calibrator; allow them to warm up for at least one
hour before performing calibration.
Press MENU, select CAL, then press ENTER. The instrument will display the
following:
CAL: VOFFSET
Use the up or down RANGE key to display the following:
CAL: UNLOCK
Press ENTER. The instrument will prompt for the calibration code:
CODE? 000000
Enter the present calibration code on the display. (Factory default: 006487.) Use
the up and down RANGE keys to select the letter or number and use the left and
right arrow keys to choose the position. Press ENTER to complete the process and
the unit will display:
CAL UNLOCKED
Followed by:
NEW CODE? N
With N displayed, press ENTER.

Offset voltage calibration
Before performing the remaining calibration steps, perform offset voltage calibration as
outlined below.
1.

2.
3.
4.
5.

From the calibration menu, use the up or down RANGE key to display the
following:
CAL: VOFFSET
Press ENTER. The instrument will prompt as follows:
INPUT CAP
Connect the triax shielding cap to the rear panel INPUT jack.
Press ENTER to complete offset voltage calibration.
Press EXIT to return to normal display.

16-8

Calibration

Model 6487 Reference Manual

Current calibration
20μA-20mA range calibration
1.
2.
3.

4.
5.
6.
7.
8.
9.
10.

11.
12.
13.

Connect the triax shielding cap to the Model 6487 rear panel INPUT jack.
Select the Model 6487 20μA range.
Press MENU, select CAL, then press ENTER. At the CAL: RUN prompt, press
ENTER. The unit will prompt for the zero calibration point:
20μA ZERO
With the triax shielding cap connected to the INPUT jack for a 0μA input current,
press ENTER.
The unit will prompt for the positive full-scale cal point:
+20μA CAL
Connect the current calibrator to the Model 6487 INPUT jack (Figure 16-1). Use
the coax cable and two adapters where shown.
Press ENTER. The unit will prompt for the positive full-scale current:
+20.00000 μA
Set the calibrator current to +20.00000μA then adjust the display to agree with the
calibrator current.
Press ENTER. The unit will prompt for the negative full-scale calibration point:
-20μA CAL
Press ENTER. The Model 6487 will prompt for the negative full-scale calibration
current:
-20.00000 μA
Set the calibrator output to –20.00000μA, then adjust the display to agree with the
calibrator value. Press ENTER to complete calibration of the present range.
Press EXIT to return to normal display.
Repeat steps 1 through 12 for the 200μA through 20mA ranges using Table 16-5 as
a guide.

Model 6487 Reference Manual

Calibration

16-9

Table 16-5
20µA to 20mA range calibration summary
Model 6487 Range
20μA

Calibrator Currents*
0μA
+20.00000μA
-20.00000μA
0μA
+200.0000μA
-200.0000μA
0mA
+2.000000mA
-2.000000mA
0mA
+20.00000mA
-20.00000mA

200μA

2mA

20mA

* Calibrate zero, positive full-scale, and negative full-scale
for each range. Triax shielding cap used for zero calibration point for all ranges. See procedure.

Figure 16-1
Connections for 20µA to 20mA range calibration
Coax Cable
INPUT
MADE IN
U.S.A.

CAT I

IEEE-488

ANALOG OUT

(CHANGE IEEE ADDRESS
WITH FRONT PANEL MENU)

DIGITAL I/O

!
505V PK
505V PK
505V PK
TRIGGER LINK

INPUT

RS-232

V-SOURCE OUTPUT
505V PK TO CHASSIS

HI INTERLOCK
505V
MAX

120

FUSE

LINE

400mAT
(SB)

100 VAC
120 VAC

200mAT
(SB)

220 VAC
240 VAC

LINE RATING
50, 60Hz
50 VA MAX

Model 6487 Picoammeter
Triax-to-BNC
Adapter

DC Current Calibrator
Dual banana-to-BNC
adapter. Connect
Output LO to shield.

2nA-2μA range calibration
1.

2.
3.

Connect the voltage calibrator and the Model 5156 Electrometer Calibration
Standard to the Model 6487 INPUT jack (Figure 16-2). Initially, make connections
to the 1GΩ resistance.
Set the calibrator to output volts and make sure the calibrator output is turned on.
Select the Model 6487 2nA range.

16-10

Calibration

Model 6487 Reference Manual

5.
6.
7.

9.
10.
11.

12.
13.

Press MENU, select CAL, then press ENTER. At the CAL: RUN prompt, press
ENTER again. The unit will prompt for the zero calibration point:
2NA ZERO
Set the calibrator voltage to 0V then press ENTER.
The instrument will prompt for the positive full-scale calibration point:
+2NA CAL
Press ENTER. The instrument will prompt for the positive full-scale calibration
current:
+2.000000 NA
Set the calibrator voltage to +2.000000V. Calculate the actual calibration current
from the calibrator voltage and the actual standard resistor value: I = V/R. Adjust
the Model 6487 display to agree with the calculated current, then press ENTER.
The Model 6487 will prompt for the negative full-scale calibration point:
-2NA CAL
Press ENTER. The instrument will prompt for the negative full-scale current:
-2.000000 NA
Set the calibrator output voltage to –2.000000V, then calculate the calibration current from the calibrator voltage and standard resistor value: I = V/R. Adjust the
Model 6487 display to agree with the calculated current, then press ENTER to
complete calibration of the present range.
Press EXIT to return to normal display.
Repeat steps 3 through 12 for the 20nA through 2μA ranges using Table 16-6 as a
guide. Be sure to make connections to the correct standard resistor and set the calibrator voltages to the correct values.

Model 6487 Reference Manual

Calibration

16-11

Table 16-6
2nA to 2µA range calibration summary
Model 6487 range

Calibrator voltages

Standard resistors1

Calibration currents2

2nA

0V
+2.000000V
-2.000000V
0V
+2.000000V
-2.000000V
0V
+200.0000V
-200.0000V

1GΩ
1GΩ
1GΩ
100MΩ
100MΩ
100MΩ
100MΩ
100MΩ
100MΩ

0nA
+2nA
-2nA
0nA
+20nA
-20nA
0μA
+2μA
-2μA

20nA

2μA

1. 1Nominal

resistance values.
Nominal currents. Calculate actual currents from calibrator voltage and actual standard resistor value: I = V/R. Calibrate zero,
positive full-scale, and negative full-scale for each range.
2

Figure 16-2
Connections for 2nA to 2µA range calibration
DC Voltage Calibrator
Model 6487 Picoammeter
BNC-to-dual
Banana Plug
Adapter

MADE IN
U.S.A.

CAT I

IEEE-488

ANALOG OUT

(CHANGE IEEE ADDRESS
WITH FRONT PANEL MENU)

DIGITAL I/O

!
505V PK
505V PK
505V PK

TRIGGER LINK

INPUT

RS-232

V-SOURCE OUTPUT
505V PK TO CHASSIS
LO

HI INTERLOCK
505V
MAX

120

FUSE

LINE

400mAT
(SB)

100 VAC
120 VAC

200mAT
(SB)

220 VAC
240 VAC

LINE RATING
50, 60Hz
50 VA MAX

Connect
Cable
Shield to
Output LO
Low-noise
Coax Cable

INPUT
Triax Cable

10GΩ

100GΩ
OUTPUT
1nF

1GΩ
!

100nF

100MΩ

Note: Connect Calibrator to
100MΩ or 1GΩ Resistor
Link Shield and Chassis

Model 5156 Calibration Standard

16-12

Calibration

Model 6487 Reference Manual

Voltage source calibration
t^okfkd

1.
2.
3.
4.
5.

7.
8.
9.

10.
11.

12.

13.
14.
15.

Hazardous voltages will be present during the following procedure.
Use care to avoid a shock hazard. The interlock must be closed to calibrate the 50V and 500V ranges. See Section 2 for interlock
information.

Set the DMM to measure DC volts and enable autoranging.
Temporarily short the ends of the DMM test leads together, then enable the DMM
REL mode. Leave REL enabled for the rest of the calibration procedure.
Connect the DMM to the Model 6487 V-SOURCE OUTPUT jacks (Figure 16-3).
Select the Model 6487 voltage source 10V range.
Press MENU, select CAL, then press ENTER. At the CAL: VSRC-RUN prompt,
press ENTER again. The unit will prompt for the negative full-range calibration
point:
V: -10V CAL
Press ENTER. The voltage source will be placed in operate and the instrument will
prompt for the negative full-scale calibration voltage:
-10.00000 V
Note the DMM voltage reading. Adjust the Model 6487 display to agree with that
voltage and then press ENTER.
Operate will turn off and the instrument will prompt for the zero calibration point:
V: 10V ZERO
Press ENTER. The voltage source will be placed in operate and the instrument will
prompt for the zero calibration voltage:
+0.00000 V
Note the DMM voltage reading. Adjust the Model 6487 display to agree with that
voltage and then press ENTER.
Operate will turn off and the unit will prompt for the positive full-range calibration
point:
V: +10V CAL
Press ENTER. The voltage source will be placed in operate and the instrument will
prompt for the positive full-scale calibration voltage:
+10.00000 V
Note the DMM voltage reading. Adjust the Model 6487 display to agree with that
voltage and then press ENTER.
Press EXIT to return to normal display.
Repeat steps 4 through 14 for the 50V and 500V ranges using Table 16-7 as a
guide.

Model 6487 Reference Manual

Calibration

16-13

Table 16-7
Voltage source calibration summary
Model 6487 Range

Calibration Voltages*

10V

-10.00000V
+0.00000V
+10.0000V
-50.00000V
+0.00000V
+50.00000V
-500.0000V
+0.00000V
+500.0000V

50V

500V

* Nominal values. Adjust display to agree with DMM reading.

Figure 16-3
Connections for voltage source calibration
Model 6487

INPUT

Model 2001 DMM
SENSE
Ω 4 WIRE

INPUT

MADE IN
U.S.A.

CAT I

IEEE-488

ANALOG OUT
350V
PEAK

!
505V PK
505V PK

2001 MULTIMETER

505V PK

DCV

ACV

DCI

ACI

Ω2

Ω4

FREQ

RANGE

TRIGGER LINK

INPUT

500V
PEAK

INPUTS

TEMP

REL

TRIG

STORE RECALL

INFO

LOCAL

CHAN

AUTO

FILTER MATH

SCAN

CONFIG MENU

EXIT

FRONT/REAR

CAL

AMPS

505V
MAX

ENTER

HI INTERLOCK

2A 250V

RANGE

POWER

RS-232

V-SOURCE OUTPUT
505V PK TO CHASSIS

120

LO
PREV

DISPLAY

(CHANGE IEEE ADDRESS
WITH FRONT PANEL MENU)

DIGITAL I/O

1100V
PEAK

FUSE

LINE

400mAT
(SB)

100 VAC
120 VAC

200mAT
(SB)

220 VAC
240 VAC

LINE RATING
50, 60Hz
50 VA MAX

V-SOURCE
OUTPUT

Entering calibration dates and saving calibration
klqb

1.
2.
3.
4.

For temporary calibration without saving new calibration constants, proceed to
“Locking out calibration”.
Press MENU, select CAL, then press ENTER to access the calibration menu.
Use either RANGE key to display the following:
CAL: SAVE
Press ENTER. The unit will prompt for today’s calibration date:
DATE: 11/15/02
Use the arrow and RANGE keys to set the date, then press ENTER. The unit will
then prompt for the calibration due date:
NDUE: 11/15/03

16-14

Calibration

Model 6487 Reference Manual

klqb

Set the calibration due date as desired then press ENTER. The unit will prompt you
as follows:
SAVE CAL?YES
With the YES prompt displayed, press ENTER to save and lock out calibration.
The unit will display:
CAL SAVED
Calibration will also be locked out once saved.

Locking out calibration
Use the following procedure to lock out calibration without saving new calibration
constants:
1.

Press MENU, select CAL, then press ENTER. Use the up RANGE key to display
the following:
CAL: LOCK
Press ENTER. The instrument will display the following message:
CAL LOCKED.

Calibration support
Changing the calibration code
Follow the steps below to change the calibration code:
1.

2.
3.
4.

5.
6.
7.

Press MENU, select CAL, then press ENTER. The instrument will display the
following:
CAL: VOFFSET
Use the up or down RANGE key to display the following:
CAL: UNLOCK
Press ENTER. The instrument will prompt for the present calibration code:
CODE? 000000
Enter the present calibration code on the display. (Factory default: 006487.) Use
the up and down RANGE keys to select the letter or number and use the left and
right arrow keys to choose the position. Press ENTER to complete the process and
the unit will display:
CAL ENABLED
Followed by:
NEW CODE? Y/N
Select Y, then press ENTER. The unit will prompt for the new code:
CODE? 000000
Enter the new code, then press ENTER.
Using the LOCK selection in the calibration menu, lock out calibration after
changing the code.

Model 6487 Reference Manual

Calibration

16-15

Resetting the calibration code
If you forget the calibration code, you can unlock calibration by shorting together the CAL
pads which are located on the display circuit board inside the unit. Doing so will also reset
the code to the factory default (006487).

Displaying calibration dates
To display calibration dates at any time:
1.

3.
4.

From normal display, press MENU, select CAL, then press ENTER. The unit will
display the following:
CAL: VOFFSET
Use either RANGE key to select CAL: DATES, then press ENTER. The
Model 6487 will display the last calibration date, for example:
DATE: 11/15/02
Press ENTER to view the calibration due date, for example:
NDUE: 11/15/03
Press EXIT to return to normal display.

Displaying the calibration count
To display the calibration count at any time:
1.

From normal display, press MENU, select CAL, then press ENTER. The unit will
display the following:
CAL: VOFFSET
Use either RANGE key to select CAL:COUNT from the calibration menu, then
press ENTER. The unit displays the calibration count, for example:
COUNT: 1
Press EXIT to return to normal display.

Routine Maintenance
•

Setting line voltage and replacing line fuse — Describes how to set the line voltage properly and replace the line fuse with the correct rating.

•

Front panel tests — Covers testing the front panel keys and the display.

17-2

Routine Maintenance

Model 6487 Reference Manual

Introduction
The information in this section deals with routine type maintenance that can be performed
by the operator and includes procedures for setting the line voltage, replacing the line fuse,
and running the front panel tests.

Setting line voltage and replacing line fuse
t^okfkd

Disconnect the line cord at the rear panel and remove all test cables
and leads connected to the instrument before replacing the line fuse.

The power line fuse is located in the power module next to the AC power receptacle
(Figure 17-1). If the line voltage must be changed or if the line fuse requires replacement,
perform the following steps:
1.

Place the tip of a flat-blade screwdriver into the power module by the fuse holder
assembly (Figure 17-1). Gently push in and to the left. Release pressure on the
assembly and its internal spring will push it out of the power module.
Remove the fuse and replace it with the type listed in Table 17-1.

t^okfkd

For continued protection against fire or instrument damage, replace
the fuse only with the type and rating listed. If the instrument repeatedly blows fuses, it will require servicing.

If configuring the instrument for a different line voltage, remove the line voltage
selector from the assembly and rotate it to the proper position. When the selector is
installed into the fuse holder assembly, the correct line voltage appears inverted in
the window.
Install the fuse holder assembly into the power module by pushing it in until it
locks in place.

Table 17-1
Line fuse ratings
Line Voltage

Rating

Keithley Part No.

100/120V

0.4A, 250V, 5 × 20mm,
slow blow

FU-106-.400

220/240V

0.2A, 250V, 5 × 20mm,
slow-blow

FU-106-.200

Model 6487 Reference Manual

Routine Maintenance

17-3

Figure 17-1
Line fuse location
Model 6487 Picoammeter

MADE IN
U.S.A.

CAT I

IEEE-488

ANALOG OUT

(CHANGE IEEE ADDRESS
WITH FRONT PANEL MENU)

DIGITAL I/O

!
505V PK
505V PK
505V PK
TRIGGER LINK

INPUT

RS-232

V-SOURCE OUTPUT
505V PK TO CHASSIS

HI INTERLOCK
505V
MAX

120

FUSE

LINE

400mAT
(SB)

100 VAC
120 VAC

200mAT
(SB)

220 VAC
240 VAC

LINE RATING
50, 60Hz
50 VA MAX

Fuse

120

Spring
Window
Fuse Holder Assembly

Front panel tests
The front panel tests are summarized in Table 17-2. To run a test, simply press the MENU
key, select TEST, and press ENTER to access the test menu. Scroll through the menu
choices with the RANGE keys and press ENTER.
Table 17-2
Front panel tests
Test

Description

DISP

Test display

KEY

Test front panel keys

17-4

Routine Maintenance

Model 6487 Reference Manual

DISP test
The display test allows you to verify that each segment and annunciator in the vacuum
fluorescent display is working properly. Perform the following steps to run the display
test:
1.
2.
3.

Press MENU, select TEST, and press ENTER to access the self-test options.
Use the up or down RANGE key to display TEST: DISP.
Press ENTER to start the test. There are four parts to the display test. Each time
ENTER is pressed, the next part of the test sequence is selected. The four parts of
the test sequence are as follows:
• All annunciators are displayed.
• The segments of each digit are sequentially displayed.
• The 12 digits (and annunciators) are sequentially displayed.
• The annunciators located at either end of the display are sequentially
displayed.
When finished, abort the display test by pressing EXIT. The instrument returns to
normal operation.

KEY test
The KEY test allows you to check the functionality of each front panel key. Perform the
following steps to run the KEY test:
1.
2.
3.

Press MENU, select TEST, and press ENTER to access the self-test options.
Use the up or down RANGE key to display TEST: KEY.
Press ENTER to start the test. When a key is pressed, the label name for that key is
displayed to indicate that it is functioning properly. When the key is released, the
message NO KEY PRESS is displayed.
Pressing EXIT tests the EXIT key. However, the second consecutive press of EXIT
aborts the test and returns the instrument to normal operation.

Specifications

6487 Picoammeter Specifications
5¹⁄₂ DIGIT
ACCURACY (1YR) 1
DEFAULT
±(% RDG. + OFFSET)
RANGE RESOLUTION 18°–28°C, 0–70% RH
2 nA
10 fA
0.3 % + 400 fA
20 nA
100 fA
0.2 % + 1 pA
200 nA
1 pA
0.15 % + 10 pA
2 µA
10 pA
0.15% + 100 pA
20 µA
100 pA
0.1 % + 1 nA
200 µA
1 nA
0.1 % + 10 nA
2 mA
10 nA
0.1 % + 100 nA
20 mA
100 nA
0.1 % + 1 µA

TYPICAL
RMS NOISE 2
20 fA
20 fA
1 pA
1 pA
100 pA
100 pA
10 nA
10 nA

TYPICAL ANALOG
RISE TIME (10% TO 90%)3
DAMPING4
OFF
ON
4 ms
80 ms
4 ms
80 ms
300 µs
1 ms
300 µs
1 ms
110 µs
110 µs
110 µs
110 µs
110 µs
110 µs
110 µs
110 µs

TEMPERATURE COEFFICIENT: 0°–18°C & 28°–50°C. For each °C, add 0.1 × (% rdg + offset) to
accuracy spec.
INPUT VOLTAGE BURDEN: <200µV on all ranges except <1mV on 20mA range.
MAXIMUM INPUT CAPACITANCE: Stable to 10nF on all nA ranges and 2µA range; 1µF on 20µA
and 200µA ranges, and on mA ranges.
MAXIMUM CONTINUOUS INPUT VOLTAGE: 505 VDC
NMRR1: (50 or 60Hz) :60dB
ISOLATION (Ammeter Common or Voltage Source to chassis): Typically >1×1011Ω in parallel
with <1nF.
MAXIMUM COMMON MODE VOLTAGE (Between Chassis and Voltage Source or Ammeter):
505 VDC.
MAXIMUM VOLTAGE BETWEEN VOLTAGE SOURCE AND AMMETER: 505 VDC
ANALOG OUTPUT: Scaled voltage output (inverting 2V full scale on all ranges) 2.5% ±2mV
ANALOG OUTPUT IMPEDANCE3: <100Ω, DC-2kHz.
VOLTAGE SOURCE
Range
(Max)

Step Size
(typical)

Accuracy5
±(% PROG. + OFFSET)
18°C - 28°C, 0 - 70% R.H.

±10.100

200µV

0.1% + 1mV

±50.500

1mV

0.1% + 4mV

±505.00

10mV

0.15% + 40mV

<1.5mV

Noise (p-p)
0.1 - 10 Hz

Temperature
Coefficient

Typical Rise
Time 6,8
(10%-90%)

Typical Fall
Time 7,8
(90%-10%)

<50µV

(0.005% + 20µV) / ˚C

250 µs

150 µs

<150µV

(0.005% + 200µV) / ˚C

250 µs

300 µs

(0.008% + 2mV) / ˚C

4.5 ms

1 ms

SELECTABLE CURRENT LIMIT: 2.5mA, 250µA, 25µA for 50V and 500V ranges, 25mA additional
limit for 10V range. All current limits are -20%/+35% of nominal.
WIDEBAND NOISE9: <30mVp-p 0.1Hz - 20MHz.
TYPICAL TIME STABILITY: ±(0.003% + 1mV) over 24 hours at constant temperature (within 1°C,
between 18°C - 28°C, after 5 minute settling).
OUTPUT RESISTANCE: <2.5Ω.
VOLTAGE SWEEPS: Supports linear voltage sweeps on fixed source range, one current or resistance measurement per step. Maximum sweep rate: 200 steps per second. Maximum step count
3000. Optional delay between step and measure.
RESISTANCE MEASUREMENT (V/I): Used with voltage source; resistance calculated from voltage
setting and measured current. Accuracy is based on voltage source accuracy plus ammeter
accuracy. Typical accuracy better than 0.6% for readings between 1kΩ and 1TΩ.
ALTERNATING VOLTAGE RESISTANCE MEASUREMENT: Offers alternating voltage resistance
measurements for resistances from 109Ω to 1015Ω. Alternates between 0V and user-selectable
voltage up to ±505V.
1

At 1 PLC – limited to 60 rdgs/sec under this condition.

At 6 PLC, 1 standard deviation, 100 readings, filter off, capped input – limited to 10 rdgs/sec
under this condition.

Measured at analog output with resistive load >2kΩ.

Maximum rise time can be up to 25% greater.

Accuracy does not include output resistance/load regulation.

Rise Time is from 0V to ± full-scale voltage (increasing magnitude).

Fall Time is from ± full-scale voltage to 0V (decreasing magnitude).

For capacitive loads, add C*ΔV/ILimit to Rise Time, and C*ΔV/1mA to Fall Time.

Measured with LO connected to chassis ground.

REMOTE OPERATION
IEEE-488 BUS IMPLEMENTATION: SCPI (IEEE-488.2, SCPI-1996.0);
DDC (IEEE-488.1).
LANGUAGE EMULATION: Keithley Model 486/487 emulation via
DDC mode.
RS-232 IMPLEMENTATION:
Supports: SCPI 1996.0.
Baud Rates: 300, 600, 1200, 2400, 4800, 9600, 19.2k, 38.4k, 57.6k.
Protocols: Xon/Xoff, 7 or 8 bit ASCII, parity-odd/even/none.
Connector: DB-9 TXD/RXD/GND.

GENERAL
AMMETER INPUT CONNECTOR: Three lug triaxial on rear panel.
ANALOG OUTPUT CONNECTOR: Two banana jacks on rear panel.
VOLTAGE SOURCE OUTPUT CONNECTOR: Two banana jacks on rear
panel.
INTERLOCK CONNECTOR: 4 pin DIN.
TRIGGER LINE: Available, see manual for usage.
DISPLAY: 12 character vacuum fluorescent.
DIGITAL FILTER: Median and averaging (selectable from 2 to 100
readings).
RANGING: Automatic or manual.
AUTORANGING TIME3: <250ms (analog filter off, 1PLC)
OVERRANGE INDICATION: Display reads “OVRFLOW”.
CONVERSION TIME: Selectable 0.01 PLC to 60 PLC (50PLC under
50Hz operation). (Adjustable from 200µs to 1s)
READING RATE:
To internal buffer 1000 readings/second1
To IEEE-488 bus
900 readings/second1, 2
BUFFER: Stores up to 3000 readings.
PROGRAMS: Provide front panel access to IEEE address, choice of
engineering units or scientific notation, and digital calibration.
EMC: Conforms with European Union Directive 89/336/EEC,
EN61326-1.
SAFETY: Conforms with European Union Directive 73/23/EEC,
EN61010-1, CAT I.
ENVIRONMENT:
Operating: 0°–50°C; relative humidity 70% non-condensing, up to
35°C. Above 35°C, derate humidity by 3% for each °C.
Storage: –10°C to +65°C.
WARM-UP: 1 hour to rated accuracy (see manual for recommended
procedure).
POWER: 100–120V or 220–240V, 50–60Hz, (50VA).
PHYSICAL:
Case Dimensions: 90mm high × 214mm wide × 369mm deep (31⁄2 in.
× 83⁄8 in. × 149⁄16 in.).
Working Dimensions: From front of case to rear including power
cord and IEEE-488 connector: 394mm (15.5 inches).
NET WEIGHT: <4.7 kg (<10.3 lbs).
Notes:
1 0.01 PLC, digital filters off, front panel off, auto zero off.
2 Binary transfer mode. IEEE-488.1.
3 Measured from trigger in to meter complete.

Specifications are subject to change without notice.

Rev. A
HW 10/25/02

Status and Error Messages

B-2

Status and Error Messages

Model 6487 Reference Manual

Table B-1
Status and error messages
Number
-440
-430
-420
-410
-363
-362
-361
-360
-350
-330
-315
-314
-285
-284
-282
-281
-260
-241
-230
-225
-224
-223
-222
-221
-220
-215
-214
-213
-212
-211
-210
-202
-201
-200
-178
-171
-170
-168
-161
-160

Description
Query unterminated after indefinite
response
Query deadlocked
Query unterminated
Query interrupted
Input buffer overrun
Framing error in program message
Parity error in program message
Communications error
Queue overflow
Save/recall memory lost
Self-test failed
Configuration memory lost
Program syntax error
Program currently running
Illegal program name
Cannot create program
Expression error
Hardware missing
Data corrupt or stale
Out of memory
Illegal parameter value
Too much data
Parameter data out of range
Settings conflict
Parameter error
Arm deadlock
Trigger deadlock
Init ignored
Arm ignored
Trigger ignored
Trigger error
Settings lost due to rtl
Invalid while in local
Execution error
Expression data not allowed
Invalid expression
Expression error
Block data not allowed
Invalid block data
Block data error

Event
EE
EE
EE
EE
EE
EE
EE
EE
SYS
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE

Model 6487 Reference Manual

Status and Error Messages

Table B-1 (cont.)
Status and error messages
Number

Description

Event

-158
-154
-151
-150
-148
-144
-141
-140
-128
-124
-123
-121
-120
-114
-113
-112
-111
-110
-109
-108
-105
-104
-103
-102
-101
-100

String data not allowed
String too long
Invalid string data
String data error
Character data not allowed
Character data too long
Invalid character data
Character data error
Numeric data not allowed
Too many digits
Exponent too large
Invalid character in number
Numeric data error
Header suffix out of range
Undefined header
Program mnemonic too long
Header separator error
Command header error
Missing parameter
Parameter not allowed
GET not allowed
Data type error
Invalid separator
Syntax error
Invalid character
Command error

EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE

+000

No error

+101
+102
+103
+104
+105
+106

Measurement events:*
Low limit 1 failed
High limit 1 failed
Low limit 2 failed
High limit 2 failed
Active limit tests passed
Reading available

SE
SE
SE
SE
SE
SE

B-3

B-4

Status and Error Messages

Model 6487 Reference Manual

Table B-1 (cont.)
Status and error messages
Number

Description

Event

+107
+108
+109
+110
+111

Reading overflow
Buffer available
Buffer full
Input overvoltage
OUTPUT interlock asserted

SE
SE
SE
SE
SE

+200

Standard events:*
Operation complete

+300
+301
+303
+305
+306
+310
+315

Operation events:*
Device calibrating
Device in A-V Ohms
Device sweeping
Waiting in trigger layer
Waiting in arm layer
Re-entering the idle layer
V-source compliance detected

SE
SE
SE
SE
SE
SE
SE

+408
+414

Questionable events:*
Questionable calibration
Command warning

SE
SE

+500
+501
+502
+507
+508
+509
+510
+511
+512
+513
+514
+515

Calibration errors:
Date of calibration not set
Next date of calibration not set
Calibration data invalid
Measurement offset data invalid
Measurement gain data invalid
Not permitted with cal locked
Not permitted with cal un-locked
Voltage offset not converging
Current offset not converging
10V Positive Vsource Offset
50V Positive Vsource Offset
500V Positive Vsource Offset

EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE

+602
+603
+604
+605
+606
+607

Lost data errors:
GPIB address lost
Power-on state lost
DC calibration data lost
Calibration dates lost
GPIB communication language lost
Vsource calibration data lost

EE
EE
EE
EE
EE
EE

Model 6487 Reference Manual

Status and Error Messages

Table B-1 (cont.)
Status and error messages
Number

Description

Event

+700
+701

Communication errors:
Invalid system communication
ASCII only with RS-232

EE
EE

+800
+801
+802
+804
+805
+806
+807
+808
+811
+812
+813
+814
+815
+816
+817
+818
+819
+820
+821
+830
+831
+840
+841
+842
+850
+851
+852
+853

Additional (more informative) command
execution errors:
Illegal with storage active
Insufficient vector data
OUTPUT blocked by interlock
Expression list full
Undefined expression exists
Expression not found
Definition not allowed
Expression cannot be deleted
Not an operator or number
Mismatched parentheses
Not a number of data handle
Mismatched brackets
Too many parentheses
Entire expression not parsed
Unknown token
Error parsing mantissa
Error parsing exponent
Error parsing value
Invalid data handle index
Invalid with INFinite ARM:COUNT
Invalid with INFinite TRIG:COUNT
Not allowed with sweep on
Sweep step size too small
Sweep step size too large
Not Allowed with A-V Ohms
Not Allowed with A-V Ohm Buffer
No A-V ohms with Autorange
Too Many A-V Ohms Readings

EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE
EE

+900

Internal system error

B-5

B-6

Status and Error Messages

Model 6487 Reference Manual

Table B-1 (cont.)
Status and error messages
Number

Description

Event

+950
+951
+952
+953
+954
+955
+956
+957
+958
+960
+961

DDC Status Model:
Rdg overflow
Rdg ready
Buffer full
IDDC error
IDDCO error
Trig overrun
No remote
Number error
DDC ready
DDC Mode IDDC Error
DDC Mode IDDCO Error

SE
SE
SE
EE
EE
EE
EE
EE
SE
EE
EE

+962
+963
+965
+966

Keithley 6487 Serial Poll Byte Events:
DDC Ready
DDC Reading Done
DDC Buffer Full
DDC Reading overflow

SE
SE
SE
SE

EE = error event
SE = status event
SYS = system error event
NOTE: Errors and status messages with a positive number are instrumentdependent. Negative errors are reserved by SCPI.
* Measurement events are flagged in Measurement Event Register, standard
events are flagged in Standard Event Register, operation events are flagged in
Operation Event Register, and questionable events are flagged in Questionable
Event Register. See Section 10 for details.

klqb

SCPI-confirmed messages are described in Volume 2: Command Reference of
the Standard Commands for Programmable Instruments. Refer to the
:SYSTem:ERRor? command.

Model 6487 Reference Manual

Status and Error Messages

B-7

Eliminating common SCPI errors
There are three SCPI errors that occur more often than any others:
•
•
•

-113, "Undefined header"
-410, "Query INTERRUPTED"
-420, "Query UNTERMINATED"

The following paragraphs discuss the most common causes for these errors and methods
for avoiding them.

-113, "Undefined header"
This error indicates that the command you sent to the instrument did not contain a recognizable command name. The most likely causes for this error are:
•

•
•

Missing space between the command and its parameter. There must be one or more
spaces (blanks) between the command and its parameter. For example:
:SOUR1:VOLT10
Incorrect (no space between command and parameter)
:SOUR1:VOLT 10
Correct
Improper short or long form. Check the command list in Section 14 for the correct
command name.
Blanks (spaces) within the command name. For example:
:SYST :ERR?
Incorrect (space between :SYST and :ERR?)
:SYST:ERR?
Correct

-410, "Query INTERRUPTED"
This error occurs when you have sent a valid query to the instrument and then send it
another command, query, or a Group Execute Trigger (GET) before it has had a chance to
send the entire response message (including the line-feed/EOI terminator). The most
likely causes are:
•

Sending a query to the instrument and then sending another command or query
before reading the response to the first query. For example, the following sequence
of commands will cause an error -410:
:SYST:ERR?
*OPC?

•

This sequence generates an error because you must read the response to
:SYST:ERR? before sending the *OPC? query.
Incorrectly configured IEEE-488 driver. The driver must be configured so that
when talking on the bus it sends line-feed with EOI as the terminator and when listening on the bus it expects line-feed with EOI as the terminator. See the reference
manual for your particular IEEE-488 interface.

B-8

Status and Error Messages

Model 6487 Reference Manual

- 420, "Query UNTERMINATED"
This error occurs when you address the instrument to talk and there is no response message to send. The most likely causes are:
•
•

•

Not sending a query. You must send a valid query to the instrument before addressing it to talk.
Sending an invalid query. If you have sent a query and still get this error, make sure
that the instrument is processing the query without error. For example, sending an
ill-formed query that generates an error -113, "Undefined header" and then
addressing the instrument to talk will generate an error -420, "Query UNTERMINATED" as well.
Valid query following an invalid command. This situation can occur when you send
multiple commands or queries (program message units) within one command
string (program message). When the Model 6487 detects an error in a program
message unit, it discards all further program message units until the end of the
string; for example:
:SENS1:DATE?; :SOUR1:VOLT?
In the above program message, the program message unit :SENS1:DATE? will generate error -113, "Undefined header" and the Model 6487 will discard the second
program message unit :SOUR1:VOLT? even though it is a valid query.

DDC Emulation Commands

C-2

DDC Emulation Commands

Model 6487 Reference Manual

DDC language
The Model 6487 can be configured to accept the device-dependent commands (DDCs) of
the Keithley Model 487 picoammeter by enabling the DDC language. To do so, use the
LANG/DDC selection in the CONFIG COMM menu, as described in “Selecting and configuring an interface,” page 9-2 in Section 9. The commands for controlling the Model
6487 with the DDC language are provided in Table C-1. For details on Model 487 operation, refer to the appropriate instruction manual PDF on the product information CD-ROM
included with your shipment.
Since the architecture of the Model 6487 differs from that of the Model 487, some commands are different and cannot be used. Be sure to refer to the notes at the end of the table
for information on command restrictions.
`^rqflk

The DDC language is intended to be used only over the IEEE-488 bus.
Using front panel controls in conjunction with this language may cause
erratic operation. In this case, results cannot be guaranteed.

Table C-1
Device dependent command summary
Mode

Command
A0

Display
Intensity

A1
A2
B0

B1
Reading
Source

B2
B3

Description
Equivalent SCPI or 488.2 commands
Normal display
DISPlay:ENABle ON
Dim display
Turn display off
DISPlay:ENABle OFF
Picoammeter readings
READ?, FETCh?, MEAS?, or
[SENSe[1]]:DATA[:LATest]?
Buffer reading (returns one at a time)
TRACe:DATA? (returns entire buffer)
All buffer readings
TRACe:DATA? (returns entire buffer)
Maximum reading from buffer
CALCulate3:FORMat MAXimum
CALCulate3:DATA?
Minimum reading from buffer
CALCulate3:FORMat MINimum
CALCulate3:DATA?

Note

Default
X

Model 6487 Reference Manual

DDC Emulation Commands

C-3

Table C-1 (cont.)
Device dependent command summary
Mode

Command
C0

Zero
Check

C1
C2

Da
Display
Text

D
F0

Ohms

F1
G0
G1
G2
G3
G4

Data
Format
G5

G6
G7

Description
Equivalent SCPI or 488.2 commands

Note

Disable Zero Check
SYSTem:ZCHeck OFF
Enable Zero Check
SYSTem:ZCHeck ON
Enable Zero Check and perform Zero Correct
SYSTem:ZCHeck ON
SYSTem:ZCORrect ON
Display ASCII text message up to 12 characters
DISPlay:TEXT
DISPlay:TEXT:STATe ON
Cancel display text mode (return to normal display)
DISPlay:TEXT:STATe OFF
Disable ohms
[SENSe[1]]:OHMS OFF
Enable ohms
[SENSe[1]]:OHMS ON
ASCII readings with prefix (NDCA-1.23456E-02)
ASCII readings without prefix (-1.23456E-02)
ASCII readings with prefix and buffer suffix (if in B1 or B2,
NDCA-1.23456E-02,012)
ASCII readings without prefix and buffer suffix (if in B1 or
B2, -1.23456E-02,012)
Binary readings, IEEE-754 std., single-precision, byte order
reversed.
FORMat:DATA SREal
FORMat:BORDer SWAPped
Binary readings, IEEE-754 std., single-precision, normal
byte order.
FORMat:DATA SREal
FORMat:BORDer NORMal
Binary readings with exponent, byte order reversed (not supported)
Binary readings with exponent, normal byte order
(not supported)

Default
X

X
X

X
SCPI not
available See
FORMat
subsystem.

C
C

C-4

DDC Emulation Commands

Model 6487 Reference Manual

Table C-1 (cont.)
Device dependent command summary
Mode

Hit Key

Self Test

Command
H1
H2
H3
H4
H5
H6
H7
H8
H11
H12
H13
H14
H15
H16
H17
H18
H19
H20
H21
H22
H23
H24
H26
H27
H28
H29
H30
H31
H32
J0
J1

Description
Equivalent SCPI or 488.2 commands
Hit CONFIG/LOCAL key
Hit I | Ω key
Hit MATH key
Hit FILT key
Hit ZCHK key
Hit REL key
Hit OPER key
Hit V-SOURCE up key
Hit RANGE up key
Hit AUTO key
Hit RANGE down key
Hit ENTER key
Hit right cursor key
Hit V-SOURCE down key
Hit MENU key
Hit COMM key
Hit DISP key
Hit TRIG key
Hit LIMIT key
Hit DIGITS key
Hit RATE key
Hit cursor left key
Hit SAVE key
Hit SETUP key
Hit STORE key
Hit RECALL key
Hit AZERO key
Hit DAMP key
Hit EXIT key
Perform RAM/ROM self-test
*TST? (Test ROM only)
Perform RAM/ROM and display self-test
*TST? (Test ROM only)

Note

Default

Model 6487 Reference Manual

DDC Emulation Commands

C-5

Table C-1 (cont.)
Device dependent command summary
Mode

EOI and
Bus
Hold-off

Default
Conditions
and
Calibration

Description
Equivalent SCPI or 488.2 commands

Command
K0

Enable both EOI and bus hold-off on X

Disable EOI, enable bus hold-off on X

Enable EOI, disable bus hold-off on X

Disable both EOI and bus hold-off on X

Return to factory defaults and save (L1)

Note
SCPI not
available
SCPI not
available
SCPI not
available
SCPI not
available

Default
X

SYSTem:PRESet
*SAV 0

Save present states as default conditions

*SAV 0

Return to saved defaults
*RCL 0

L3-L6

Calibration commands (not supported)

Clears SRQ mask (SRQ disabled)

G
SRQ Mask
Bits:
(H)
(None)

*SRE 0

Reading Overflow
STATus:MEASurement[:EVENt]:ENABle 128
*SRE 1

Data Store Full
STATus:MEASurement[:EVENt]:ENABle 512
*SRE 1

SRQ
M4

Data Store Half Full
(not SCPI supported)

Reading Done
STATus:MEASurement[:EVENt]:ENABle 64
*SRE 1

M16

Ready

M32

Error

M128

Voltage source error

(B0)
page C-14
(B1)
page C-14
(B2)
page C-14
(B3)
page C-14
(B4)
page C-14, I
(B5)
page C-14, I
(B7)
page C-15, I

C-6

DDC Emulation Commands

Model 6487 Reference Manual

Table C-1 (cont.)
Device dependent command summary
Mode
Data Store

Operate

Command
N0
Nn
O0

Description
Equivalent SCPI or 488.2 commands
Stop storage, clear buffer
Arm data store, set buffer size “n” where n =1 to 512
Place voltage source in standby

Note

Default

J
J
X

SOURce[1]:VOLTage:STATe OFF

Place voltage source in operate
SOURce[1]:VOLTage:STATe ON

Filters

Interval

P0
P1
P2
P3
Q0
Q1
R0

Both analog and digital filters off
Enable digital filter, disable analog filter
Disable digital filter, enable analog filter
Enable both digital and analog filters
175msec
TRIGger:DELay 0.175
Set to “n” seconds, n= 0.01msec to 999.999sec
TRIGger:DELay
Enable autorange

K
K

X
L
X

[SENSe[1]]:RANGe:AUTO ON

2nA range
[SENSe[1]]:RANGe 2e-9

20nA range
[SENSe[1]]:RANGe 20e-9

200nA range
[SENSe[1]]:RANGe 200e-9

2μA range
[SENSe[1]]:RANGe 2e-6

Range

20μA range
[SENSe[1]]:RANGe 20e-6

200μA range
[SENSe[1]:RANGe 200e-6

2mA range
[SENSe[1]]:RANGe 2e-3

20mA range

[SENSe[1]]:RANGe 20e-3

20mA range

[SENSe[1]]:RANGe 20e-3

R10

Disable autorange
[SENSe[1]]:RANGe:AUTO OFF

Model 6487 Reference Manual

DDC Emulation Commands

C-7

Table C-1 (cont.)
Device dependent command summary
Mode

Command
S0

Integration
Period

Description
Equivalent SCPI or 488.2 commands

Note

Default

Fast integration (1.6msec at 4-1/2 digit resolution)
[SENSe[1]]:FUNCtion:NPLCycles 0.1 (at 60Hz)

Line cycle (16.67msec, 60Hz; 20msec, 50Hz; 5-1/2d)
[SENSe[1]]:FUNCtion:NPLCycles 1.0 (at 60Hz)

Continuous, triggered by talk

One-shot, triggered by talk
ARM[:SEQuence[1]]:COUNt 1
TRIGger[:SEQuence[1]]:COUNt 1

SCPI not
available
Only in
488.1 mode

Continuous, triggered by GET
ARM[:SEQuence[1]]:SOURce BUS
ARM[:SEQuence[1]]:COUNt 1
TRIGger[:SEQuence[1]]:COUNt INF
INIT[:IMMediate]

One-shot, triggered by GET
ARM[:SEQuence[1]]:SOURce BUS
ARM[:SEQuence[1]]:COUNt INF
TRIGger[:SEQuence[1]]:COUNt 1
INIT[:IMMediate]

Trigger
Mode

Continuous, triggered by X

One-shot, triggered by X

Continuous, triggered by External Trigger

SCPI Not
Available
SCPI Not
Available
X

ARM[:SEQuence[1]]:SOURce TLINk
ARM[:SEQuence[1]]:SOURce COUNt 1
TRIGger[:SEQuence[1]]:COUNt INF
INITiate[:IMMediate]

One-shot, triggered by External Trigger
ARM[:SEQuence[1]]:SOURce TLINk
ARM[:SEQuence[1]]:SOURce COUNt INF
TRIGger[:SEQuence[1]]:COUNt 1
INITiate[:IMMediate]

Continuous on Operate

One-shot on Operate

SCPI Not
Available
SCPI Not
Available

C-8

DDC Emulation Commands

Model 6487 Reference Manual

Table C-1 (cont.)
Device dependent command summary
Mode

Command
U0

U1
U2
U3
Status
Word

U4
U5
U6
U7
U8
U9
Vn,r,l

Voltage
Source

Delay
Execute

Terminator

Wn
X
Y0
Y1
Y2
Y3
Y4

Description
Equivalent SCPI or 488.2 commands
Return status word. See Figure C-1. Each SCPI
parameter must be queried individually. For example:
SENSe[1]:CURRent:RANGe?
Send error conditions. See Figure C-2.
Send model number and firmware revision
SYSTem:VERsion?
Send calibration value
CALibration:PROTected:SENSe:DATA?
Send interval
ARM:TIMer?
Send delay
TRIGger:DELay?
Send relative value for current
CALCulate[1]:NULL:OFFSet?
Send relative value for V/I ohms
CALCulate[1]:NULL:OFFSet?
Send voltage source value
SOURce[1]:VOLtage?
Send voltage source status word. See Figure C-3.
Voltage source value, range, current limit
n = -505 to 505
SOURce[1]:VOLTage
r: 0 = 50V range; 1 = 500V range
SOURce[1]:VOLTage:RANge
l: 0 = 25μA limit; 1 = 2.5mA limit
SOURce[1]:VOLTage:ILIMit
Delay trigger for “n’ seconds. n = 0 to 999.999sec
TRIGger:DELay
Execute other device-dependent commands. SCPI not applicable (SCPI commands execute as they are received)
CR LF (carriage return, line feed)
LF CR (line feed, carriage return)
CR (carriage return)
LF (line feed)
N
None

Note

Default

0V
50V
2.5mA
0

Model 6487 Reference Manual

DDC Emulation Commands

C-9

Table C-1 (cont.)
Device dependent command summary
Mode

Command
Z0

Description
Equivalent SCPI or 488.2 commands
Disable relative

Note

Default
X

CALCulate[1]:NULL:STATe OFF

Z1
Relative
(REL)

Enable relative using present reading as baseline
CALCulate[1]:NULL:ACQuire
CALCulate[1]:NULL:STATe ON

Z2,V

Enable relative using V as baseline: V = -2e-2 to 2e-2A for
current. V = 0Ω to 50.5e16Ω for V/I ohms.
CALCulate2:NULL:OFFSet
CALCulate2:NULL:STATe ON

Enable relative using previously defined baseline
CALCulate[1]:NULL:STATe ON

A) Only characters will be dimmed. Annunciators will not be dimmed.
B) Zero Correct and Zero Correct notes:
a. Sending C2X will perform a Zero Correct operation. If the unit is not
already in Zero Check, then Zero Check will be turned on first, then the
Zero Correct value collected, then Zero Check will be turned off.
b. The 487 offers no way to "turn off" Zero Correct. Once a C2 command
has been sent, Zero Correct (and the corresponding MON annunciator)
will remain on. To turn off the Zero Correct and MON annunciator, use
the front panel to turn off Zero Correct.
c. Like the 487, subsequent C2 commands will cause a new Zero Correct
value to be acquired.
d. The 6487 saves only a single Zero Correct value, not one for each range
as with the 487. For best results, send a C2 command to acquire new Zero
Correct value after going to the desired range. Also, unlike the 487, Zero
Correct values are not saved across power cycles and must be re-acquired
after power cycling the unit.
C) G6 and G7 are not supported by the Model 6487 since they are seldom used.
D) The Model 487 uses different keys and menu structure than the Model 6487, so
key mapping is not comparable.
E) The J commands (J0, J1) for RAM and ROM self-tests will be accepted but take no
action. RAM and ROM are tested at power-up. The display may be tested from the
front panel.

C-10

DDC Emulation Commands

Model 6487 Reference Manual

Since the Model 487 DDC Mode allows for one saved user setup to be the poweron default, the *SAV 0 location is used for the saved DDC defaults. Therefore,
changing the instrument language to DDC will clear out the *SAV 0 location and
load it with the DDC factory defaults. A setup saved using the DDC mode L1 command will be saved into this location. Likewise, changing the Model 6487 language
from DDC mode to SCPI will return the SYST:PRESet factory defaults into the
*SAV 0 setup location, overwriting the setup that had been stored with the DDC
mode L1 command.
G) Calibration can be performed only with SCPI calibration commands. See
Appendix F.
H) Multiple SRQ conditions can be enabled by adding up M command values. For
example, M33 enables SRQ both on reading done and on error.

L)
M)

N)
klqb

The DDC errors do not map one-to-one with SCPI errors. There are two SCPI
errors that cover all of the 6487 Error Events (EE). This will be fairly equivalent
to using the M16 DDC command. After getting an SRQ on an Error Event, to
clear the event, read the Standard Event Register (*ESR?, then talk the instrument). There may also be an Error Available event set in the status byte (serial
poll).
Buffer operating notes:
a. The 6487 does not support a continuous wrap-around buffer. Therefore,
the N0 command will simply stop storage and clear the buffer.
b. Nx (x=1-512) will arm the buffer and storage will commence at the first
trigger. A key difference between the 487 and the 6487 is that pressing
the LOCAL key on a 6487 puts the unit back into continuous trigger
mode, so storage will start immediately. On the 487, however, you must
press LOCAL followed by a separate press of the TRIGGER key. If all
triggering is handled over the GPIB, this difference will not matter in
actual practice. Although the 6487 buffer is capable of storing 3000 readings, in DDC mode the limit is the same 512 readings as the 487.
The digital filter is always a 4-point moving average type and cannot be changed in
DDC mode.
See ARM and TRIGger subsystems in Section 14.
The 487 does not allow R8 or R9, since its highest measurement range is R7,
which is the 2mA range. The 6487 accepts R8 and R9, both of which select the
20mA range. Whether R8 or R9 is sent, an '8' will show up in the range position
of the U0 response string. R10 is still used to disable auto range and remain on
the present range as in the 487.
SCPI PMT (Program Message Terminator) is always LF + EOI.

DDC timing is not guaranteed to match the timing of the original instrument
(487) being emulated.

Model 6487 Reference Manual

DDC Emulation Commands

C-11

Sweeps or A-V ohms in DDC mode
Sweeps or A-V ohms are not allowed in the DDC mode. A “SCPI ONLY” message will be
displayed if you attempt to use sweeps or A-V ohms from the front panel.

Status words
The U0, U2, and U9 status words are shown in Figure C-1, Figure C-2, and Figure C-3.

C-12

DDC Emulation Commands

Model 6487 Reference Manual

Figure C-1
U0 machine status word
Status Word

OPERATE
0 = Off*
1 = On

READING SOURCE
0 = Picoammeter*
1 = One buffer reading
2 = All buffer readings
3 = Max. buffer reading
4 = Min. buffer reading

FILTERS
0 = Both off
1 = A off, D on
2 = A on, D off
3 = Both on*

ZERO CHECK
0 = Disabled*
1 = Enabled

RANGE
0 = Auto Off
1 = Auto On*
1 = 2nA
2 = 20nA
3 = 200nA
4 = 2μA
5 = 20μA
6 = 200μA
7 = 2mA
8 = 20mA

V/I OHMS
0 = Disabled*
1 = Enabled
DATA FORMAT
0 = Rdg with prefix (ASCII)*
1 = Rdg without prefix (ASCII)
2 = Rdg, buffer location with prefix
3 = Rdg, buffer location without prefix
4 = Binary rdg, byte reversed
5 = Binary rdg, normal byte order
HIT BUTTON
01 = CONFIG
02 = I | Ω
03 = MATH
04 = FILT
05 = ZCHK
06 = REL
07 = OPER
08 = SOURCE Up
11 = RANGE Up
12 = AUTO
13 = RANGE Down
14 = ENTER
15 = Cursor Right
16 = SOURCE Down
17 = MENU

18 = COMM
19 = DISP
20 = TRIG
21 = LIMIT
22 = DIGITS
23 = RATE
24 = Cursor Left
26 = SAVE
27 = SETUP
28 = STORE
29 = RECALL
30 = AZERO
31 = DAMP
32 = EXIT

SELF TEST
0 = No error*
1 = ROM error
EOI, HOLD-OFF
0 = EOI & hold-off*
1 = No EOI, hold-off
2 = EOI, no hold-off
3 = No EOI, no hold-off

DATA STORE SIZE
000 = Disabled*
nnn = 001 to 512 (size)

SRQ MASK**
000 = SRQ Disabled*
001 = Reading Overflow
002 = Data Store Full
004 = Data Store 1/2 Full
008 = Reading Done
016 = Ready
032 = Error
128 = V-source Error

*Default settings
**Add up values for multiple SRQ conditions

CAL LOCK
0 = Locked*
1 = Unlocked

PREFIX
DISPLAY INTENSITY
0 = Normal*
1 = Dim (Characters)
2 = Off

RELATIVE
0 = Off*
1 = On
TERMINATOR
0 = CR LF*
1 = LF CR
2 = CR
3 = LF
4 = None
V-SOURCE
00 = 50V rg, 25μA lim
01 = 50V rg, 2.5mA lim*
10 = 500V rg, 25μA lim
11 = 500V rg, 2.5mA lim

INTEGRATION
0 = Fast
1 = Line cycle*

TRIGGER
0 = Continuous on Talk
1 = One-shot on Talk
2 = Continuous on Get
3 = One-shot on Get
4 = Continuous on “X”
5 = One-shot on “X”
6 = Continuous on Ext Trig*
7 = One-shot on Ext Trig
8 = Contiuous on Operate
9 = One-shot on Operate

Model 6487 Reference Manual

DDC Emulation Commands

C-13

Figure C-2
U1 error status word
1 = IDDC
1 = IDDCO

1 = V-Source
1 = V-Source Conflict

487 1/0 1/0 1/0 1/0 1/0 1/0 1/0 1/0 1/0 1/0 1/0 1/0 1/0
1 = E 2PROM
Cal Constants

1= No Remote

1 = E PROM Defaults

1 = Self-Test

1= Calibration

1 = Trigger Overrun
1 = Conflict

1= Zero Check

1 = Cal Locked

Figure C-3
U9 voltage source status word

487 1/0 1/0
1= Interlock Open
1 = Current Limit

Status byte format
The status byte contains information relating to data and error conditions within the instrument. When a particular bit is set, certain conditions are present. Table C-2 lists the meanings of the various bits and Figure C-4 shows the general format of the status byte, which
is obtained by using the SPE, SPD polling sequence.
If the status byte is read when no SRQ was generated by the Model 6487 (bit 6 is clear),
the current status of the instrument will be read. For example, if a reading was done, bit 3
would be set.
SRQ is enabled by setting the corresponding bit with the SRQ mask using the M command (see Table C-1). The Model 6487 may be programmed to generate an SRQ for more
than one condition simultaneously, simply by adding up the command option values.

C-14

DDC Emulation Commands

Model 6487 Reference Manual

When an SRQ is generated by the Model 6487, bit 6 of the status byte will be set. After an
SRQ, the status byte will remain unchanged until it is read.
The various bits in the status byte are described below:
Reading Overflow (B0) — Set when an overrange input is applied to the instrument.
Cleared when on on-scale reading has been made.
Data Store Full (B1) — Set when the number of readings stored is equal to the buffer
size. Cleared by re-arming data store.
Data Store 1/2 Full (B2) — Set when the number of readings stored is equal to half the
buffer size. Cleared by re-arming data store.
Reading Done (B3) — Set when the instrument has completed the present conversion and
is ready to take another reading. Cleared when the reading has been sent.
Ready (B4) — Set when the instrument has processed all previous commands and is
ready to begin processing new commands or triggers. Cleared while instrument is processing commands or triggers.
Error (B5) — Set when one of the following errors has occurred:
–
–
–
–
–
–
–
–
–
–
–
–
–

IDDC
IDDCO
No remote
Self test
Trigger overrun
Conflict
Cal locked
Zero check
Calibration error
E2PROM defaults error
E2PROM cal constants error
V-source conflict
Interlock

This bit is cleared when the U1 status word is read to determine the nature of the error (see
Figure C-2.)
RQS (B6) — Set when the Model 6487 has generated a request for service via the SRQ
line. Cleared by reading the status byte.

Model 6487 Reference Manual

DDC Emulation Commands

C-15

Voltage Source Error (B7) — Set if the voltage source has reached current limit or if the
interlock is tripped. Cleared by reading U9 status after correcting the voltage source error
(see Figure C-3).
klqb

Once the Model 6487 has generated an SRQ, its status byte must be read to
clear the SRQ line. Otherwise, the instrument will continuously assert SRQ.

Table C-2
Status byte and SRQ mask interpretation
Bit

Decimal
Weighting

Description

0 (LSB)
1
2
3
4
5
6
7

1
2
4
8
16
32
64
128

Reading Overflow
Data Store Full
Data Store 1/2 Full
Reading done
Ready
Error
RQS (Request for Service)*
Voltage Source Error

* Status byte only

Figure C-4
Status byte format

MSB

V-source
Error

RQS*

Error

Ready

* Status bye only

Data
Reading Store
Done 1/2 Full
B3

Data
Store Reading
Full Overflow
B1

LSB

IEEE-488 Bus Overview
•

Bus description – This section gives a detailed description of the bus. Introduces
and defines the controller, talker, and listener.

•

Bus lines – This section describes the operation of data lines, bus management
lines, and handshake lines.

•

Bus commands – This section describes the purpose of bus commands, lists the
three catagories of bus commands, and defines the three catagories.

•

Interface function codes – This section lists and defines the interfce function
codes for the Model 6487.

D-2

IEEE-488 Bus Overview

Model 6487 Reference Manual

Introduction
The IEEE-488 bus is a communication system between two or more electronic devices. A
device can be either an instrument or a computer. When a computer is used on the bus, it
serves as a supervisor of the communication exchange between all the devices and is
known as the controller. Supervision by the controller consists of determining which
device will talk and which device will listen. As a talker, a device will output information;
as a listener, a device will receive information. To simplify the task of keeping track of the
devices, a unique address number is assigned to each.
On the bus, only one device can talk at a time and is addressed to talk by the controller.
The device that is talking is known as the active talker. The devices that need to listen to
the talker are addressed to listen by the controller. Each listener is then referred to as an
active listener. Devices that do not need to listen are instructed to unlisten. The reason for
the unlisten instruction is to optimize the speed of bus information transfer since the task
of listening takes up bus time.
Through the use of control lines, a handshake sequence takes place in the transfer process
of information from a talker to a listener. This handshake sequence helps ensure the credibility of the information transfer. The basic handshake sequence between an active controller (talker) and a listener is as follows:
1.
2.
3.
4.
5.

The listener indicates that it is ready to listen.
The talker places the byte of data on the bus and indicates that the data is available
to the listener.
The listener, aware that the data is available, accepts the data and then indicates
that the data has been accepted.
The talker, aware that the data has been accepted, stops sending data and indicates
that data is not being sent.
The listener, aware that there is no data on the bus, indicates that it is ready for the
next byte of data.

Model 6487 Reference Manual

IEEE-488 Bus Overview

D-3

Bus description
The IEEE-488 bus, which is also referred to as the GPIB (General Purpose Interface Bus),
was designed as a parallel transfer medium to optimize data transfer without using an
excessive number of bus lines. In keeping with this goal, the bus has only eight data lines
that are used for both data and with most commands. Five bus management lines and three
handshake lines round out the complement of bus signal lines.
A typical setup for controlled operation is shown in Figure D-1. Generally, a system will
contain one controller and a number of other instruments to which the commands are
given. Device operation is categorized into three operators: controller, talker, and listener.
The controller controls the instruments on the bus. The talker sends data while a listener
receives data. Depending on the type of instrument, any particular device can be a talker
only, a listener only, or both a talker and listener.
There are two categories of controllers: system controller and basic controller. Both are
able to control other instruments, but only the system controller has the absolute authority
in the system. In a system with more than one controller, only one controller may be active
at any given time. Certain protocol is used to pass control from one controller to another.
The IEEE-488 bus is limited to 15 devices, including the controller. Thus, any number of
talkers and listeners up to that limit may be present on the bus at one time. Although several devices may be commanded to listen simultaneously, the bus can have only one active
talker or communications would be scrambled.
A device is placed in the talk or listen state by sending an appropriate talk or listen command. These talk and listen commands are derived from an instrument’s primary address.
The primary address may have any value between 0 and 31, and is generally set by rear
panel DIP switches or programmed in from the front panel of the instrument. The actual
listen address value sent out over the bus is obtained by ORing the primary address with
$20. For example, if the primary address is $14, the actual listen address is $34 ($34 = $14
+ $20). In a similar manner, the talk address is obtained by ORing the primary address
with $40. With the present example, the talk address derived from a primary address of
$14 would be $54 ($54 = $14 + $40).
The IEEE-488 standards also include another addressing mode called secondary addressing. Secondary addresses lie in the range of $60-$7F. Note, however, that many devices,
including the Model 6487, do not use secondary addressing.
Once a device is addressed to talk or listen, the appropriate bus transactions take place. For
example, if the instrument is addressed to talk, it places its data string on the bus one byte
at a time. The controller reads the information and the appropriate software can be used to
direct the information to the desired location.

D-4

IEEE-488 Bus Overview

Model 6487 Reference Manual

Figure D-1
IEEE-488 bus configuration
TO OTHER DEVICES

DEVICE 1
ABLE TO
TALK, LISTEN
AND CONTROL
(COMPUTER)
DATA BUS
DEVICE 2
ABLE TO
TALK AND
LISTEN
(6487)
2182

DEVICE 3
ONLY ABLE
TO LISTEN
(PRINTER)

DATA BYTE
TRANSFER
CONTROL

GENERAL
INTERFACE
MANAGEMENT

DEVICE 4
ONLY ABLE
TO TALK

DIO 1–8 DATA
(8 LINES)

DAV
NRFD
NDAC
IFC
ATN
SRQ
REN
EOI

HANDSHAKE

BUS
MANAGEMENT

Bus lines
The signal lines on the IEEE-488 bus are grouped into three different categories: data
lines, management lines, and handshake lines. The data lines handle bus data and commands, while the management and handshake lines ensure that proper data transfer and
operation takes place. Each bus line is active low, with approximately zero volts representing a logic 1 (true). The following paragraphs describe the operation of these lines.

Model 6487 Reference Manual

IEEE-488 Bus Overview

D-5

Data lines
The IEEE-488 bus uses eight data lines that transfer data one byte at a time. DIO1 (Data
Input/Output) through DIO8 (Data Input/Output) are the eight data lines used to transmit
both data and multiline commands and are bi-directional. The data lines operate with low
true logic.

Bus management lines
The five bus management lines help to ensure proper interface control and management.
These lines are used to send the uniline commands.
ATN (Attention) — The ATN state determines how information on the data bus is to be
interpreted.
IFC (Interface Clear) — The IFC line controls clearing of instruments from the bus.
REN (Remote Enable) — The REN line is used to place the instrument on the bus in the
remote mode.
EOI (End or Identify) — The EOI line is used to mark the end of a multi-byte data
transfer sequence.
SRQ (Service Request) — The SRQ line is used by devices when they require service
from the controller.

Handshake lines
The bus handshake lines operate in an interlocked sequence. This method ensures reliable
data transmission regardless of the transfer rate. Generally, data transfer will occur at a
rate determined by the slowest active device on the bus.
One of the three handshake lines is controlled by the source (the talker sending information), while the remaining two lines are controlled by accepting devices (the listener or listeners receiving the information). The three handshake lines are:
DAV (DATA VALID) — The source controls the state of the DAV line to indicate to any
listening devices whether or not data bus information is valid.
NRFD (Not Ready For Data) — The acceptor controls the state of NRFD. It is used to
signal to the transmitting device to hold off the byte transfer sequence until the accepting
device is ready.
NDAC (Not Data Accepted) — NDAC is also controlled by the accepting device. The
state of NDAC tells the source whether or not the device has accepted the data byte.
The complete handshake sequence for one data byte is shown in Figure D-2. Once data is
placed on the data lines, the source checks to see that NRFD is high, indicating that all
active devices are ready. At the same time, NDAC should be low from the previous byte
transfer. If these conditions are not met, the source must wait until NDAC and NRFD have

D-6

IEEE-488 Bus Overview

Model 6487 Reference Manual

the correct status. If the source is a controller, NRFD and NDAC must be stable for at least
100ns after ATN is set true. Because of the possibility of a bus hang up, many controllers
have time-out routines that display messages in case the transfer sequence stops for any
reason.
Once all NDAC and NRFD are properly set, the source sets DAV low, indicating to accepting devices that the byte on the data lines is now valid. NRFD will then go low, and NDAC
will go high once all devices have accepted the data. Each device will release NDAC at its
own rate, but NDAC will not be released to go high until all devices have accepted the data
byte.
The previous sequence is used to transfer both data, talk, and listen addresses, as well as
multiline commands. The state of the ATN line determines whether the data bus contains
data, addresses, or commands as described in the following paragraphs.
Figure D-2
IEEE-488 handshake sequence
DATA

SOURCE

DAV

SOURCE
VALID
ALL READY

ACCEPTOR

NRFD
ALL ACCEPTED
NDAC

ACCEPTOR

Bus commands
The instrument may be given a number of special bus commands through the IEEE-488
interface. The following paragraphs briefly describe the purpose of the bus commands
which are grouped into the following three categories.
1.
2.
3.
4.

Uniline commands — Sent by setting the associated bus lines true. For example,
to assert REN (Remote Enable), the REN line would be set low (true).
Multiline commands — General bus commands which are sent over the data lines
with the ATN line true (low).
Common commands — Commands that are common to all devices on the bus;
sent with ATN high (false).
SCPI commands — Commands that are particular to each device on the bus; sent
with ATN (false).

Model 6487 Reference Manual

IEEE-488 Bus Overview

These bus commands and their general purpose are summarized in Table D-1.
Table D-1
IEEE-488 bus command summary
Command
type

Command

State of
ATN line

Comments

Uniline

REN (Remote Enable)
EOI
IFC (Interface Clear)
ATN (Attention)
SRQ

X
X
X
Low
X

Set up devices for remote operation.
Marks end of transmission.
Clears interface.
Defines data bus contents.
Controlled by external device.

Multiline
Universal

LLO (Local Lockout)
DCL (Device Clear)
SPE (Serial Enable)
SPD (Serial Poll Disable)

Low
Low
Low
Low

Locks out local operation.
Returns device to default conditions.
Enables serial polling.
Disables serial polling.

Addressed

SDC (Selective Device Clear)
GTL (Go To Local)

Low
Low

Returns unit to default conditions.
Returns device to local.

Unaddressed

UNL (Unlisten)
UNT (Untalk)

Low
Low

Removes all listeners from the bus.
Removes any talkers from the bus.

Common

—

High

SCPI

—

High

Programs IEEE-488.2 compatible instruments for common operations.
Programs SCPI compatible instruments for
particular operations.

D-7

D2
⎠

D3
⎠

D1
⎠

D0
⎠

Column♦
Row ⎠

Command

UNIVERSAL
COMMAND
GROUP
(UCG)

SPD

SPE

PPU*

DCL

LLO

1 (B)

ADDRESSED
COMMAND
GROUP
(ACG)

ESC

SUB

CAN

ETB

SYN

NAK

DC4

DC3

DC2

DC1

DLE

1 (A)

TCT*

GET

PPC*

SDC

GTL

0 (B)

X
0
0
1
Command

BEL

ACK

ENQ

EOT

ETX

STX

SOH

NUL

0 (A)

X
0
0
0

•

)

(

‘

“

2 (A)

X
0
1
0
Primary
Address
?

;

3 (A)

PRIMARY
COMMAND
GROUP
(PCG)

LISTEN
ADDRESS
GROUP
(LAG)

2 (B)

X
0
1
1
Primary
Address
UNL

3(B)

4 (A)

X
1
0
0
Primary
Address
∞

]

[

5 (A)

TALK
ADDRESS
GROUP
(TAG)

4 (B)

X
1
0
1

UNT

5 (B)

6 (A)

X
1
1
0

DEL

≅

}

{

7 (A)

SECONDARY
COMMAND
GROUP
(SDC)

6 (B)

X
1
1
1

7 (B)

IEEE-488 Bus Overview

*PPC (PARALLEL POLL CONFIGURE) PPU (PARALLEL POLL UNCONFIGURE),
6514.
and TCT (TAKE CONTROL) not implemented by Model 2182.
Note: D0 = DIO1 ... D7 = DIO8; X = Don’t Care.

Bits

D7
D6
D5
D4
Primary
Address

D-8
Model 6487 Reference Manual

Table D-2
Command codes

Model 6487 Reference Manual

IEEE-488 Bus Overview

D-9

Uniline commands
ATN, IFC, and REN are asserted only by the controller. SRQ is asserted by an external
device. EOI may be asserted either by the controller or other devices depending on the
direction of data transfer. The following is a description of each command. Each command
is sent by setting the corresponding bus line true.
REN (Remote Enable) — REN is sent to set up instruments on the bus for remote operation. When REN is true, devices will be removed from the local mode. Depending on
device configuration, all front panel controls, except the LOCAL button (if the device is so
equipped), may be locked out when REN is true. Generally, REN should be sent before
attempting to program instruments over the bus.
EOI (End or Identify) — EOI is used to positively identify the last byte in a multi-byte
transfer sequence, thus allowing data words of various lengths to be transmitted easily.
IFC (Interface Clear) — IFC is used to clear the interface and return all devices to the
talker and listener idle states.
ATN (Attention) — The controller sends ATN while transmitting addresses or multiline
commands.
SRQ (Service Request) — SRQ is asserted by a device when it requires service from a
controller.

Universal multiline commands
Universal commands are those multiline commands that require no addressing. All devices
equipped to implement such commands will do so simultaneously when the commands
are transmitted. As with all multiline commands, these commands are transmitted with
ATN true.
LLO (Local Lockout) — LLO is sent to the instrument to lock out the LOCAL key and all
their front panel controls.
DCL (Device Clear) — DCL is used to return instruments to some default state. Instruments usually return to their power-up conditions.
SPE (Serial Poll Enable) — SPE is the first step in the serial polling sequence which is
used to determine which device has requested service.
SPD (Serial Poll Disable) — SPD is used by the controller to remove all devices on the
bus from the serial poll mode and is generally the last command in the serial polling
sequence.

D-10

IEEE-488 Bus Overview

Model 6487 Reference Manual

Addressed multiline commands
Addressed commands are multiline commands that must be preceded by the device listen
address before that instrument will respond to the command in question. Note that only
the addressed device will respond to these commands. Both the commands and the address
preceding it are sent with ATN true.
SDC (Selective Device Clear) — The SDC command performs essentially the same
function as the DCL command except that only the addressed device responds. Generally,
instruments return to their power-up default conditions when responding to the SDC
command.
GTL (Go To Local) — The GTL command is used to remove instruments from the
remote mode. With some instruments, GTL also unlocks front panel controls if they were
previously locked out with the LLO command.
GET (Group Execute Trigger) — The GET command is used to trigger devices to perform a specific action that depends on device configuration (for example, take a reading).
Although GET is an addressed command, many devices respond to GET without
addressing.

Address commands
Addressed commands include two primary command groups and a secondary address
group. ATN is true when these commands are asserted. The commands include:
LAG (Listen Address Group) — These listen commands are derived from an instrument’s primary address and are used to address devices to listen. The actual command
byte is obtained by ORing the primary address with $20.
TAG (Talk Address Group) — The talk commands are derived from the primary address
by ORing the address with $40. Talk commands are used to address devices to talk.
SCG (Secondary Command Group) — Commands in this group provide additional
addressing capabilities. Many devices (including the Model 6487) do not use these
commands.

Unaddress commands
The two unaddress commands are used by the controller to remove any talkers or listeners
from the bus. ATN is true when these commands are asserted.
UNL (Unlisten) — Listeners are placed in the listener idle state by the UNL command.
UNT (Untalk) — Any previously commanded talkers will be placed in the talker idle
state by the UNT command.

Model 6487 Reference Manual

IEEE-488 Bus Overview

D-11

Common commands
Common commands are commands that are common to all devices on the bus. These commands are designated and defined by the IEEE-488.2 standard.
Generally, these commands are sent as one or more ASCII characters that tell the device to
perform a common operation, such as reset. The IEEE-488 bus treats these commands as
data in that ATN is false when the commands are transmitted.

SCPI commands
SCPI commands are commands that are particular to each device on the bus. These commands are designated by the instrument manufacturer and are based on the instrument
model defined by the Standard Commands for Programmable Instruments (SCPI) Consortium’s SCPI standard.
Generally, these commands are sent as one or more ASCII characters that tell the device to
perform a particular operation, such as setting a range or closing a relay. The IEEE-488
bus treats these commands as data in that ATN is false when the commands are
transmitted.

Command codes
Command codes for the various commands that use the data lines are summarized in
Table D-2. Hexadecimal and the decimal values for the various commands are listed in
Table D-3.
Table D-3
Hexadecimal and decimal command codes
Command

Hex value

Decimal value

GTL
SDC
GET
LLO
DCL
SPE
SPD
LAG
TAG
SCG
UNL
UNT

01
04
08
11
14
18
19
20-3F
40-5F
60-7F
3F
5F

1
4
8
17
20
24
25
32-63
64-95
96-127
63
95

D-12

IEEE-488 Bus Overview

Model 6487 Reference Manual

Typical command sequences
For the various multiline commands, a specific bus sequence must take place to properly
send the command. In particular, the correct listen address must be sent to the instrument
before it will respond to addressed commands. Table D-4 lists a typical bus sequence for
sending the addressed multiline commands. In this instance, the SDC command is being
sent to the instrument. UNL is generally sent as part of the sequence to ensure that no
other active listeners are present. Note that ATN is true for both the listen command and
the SDC command byte itself.
Table D-4
Typical bus sequence
Data bus
Step
1
2
3
4

Command
UNL
LAG*
SDC

ATN state
Set low
Stays low
Stays low
Returns high

ASCII

Hex

63
54
4

3F
36
04

?
.
EOT

Decimal

*Assumes primary address = 22.

Table D-5 gives a typical common command sequence. In this instance, ATN is true while
the instrument is being addressed, but it is set high while sending the common command
string.
Table D-5
Typical addressed command sequence
Data bus
Step
1
2
3
4
5
6

Command
UNL
LAG*
Data
Data
Data
Data

*Assumes primary address = 22.

ATN state
Set low
Stays low
Set high
Stays high
Stays high
Stays high

ASCII

Hex

Decimal

?
.
*
R
S
T

3F
36
2A
52
53
54

63
54
42
82
83
84

Model 6487 Reference Manual

IEEE-488 Bus Overview

D-13

IEEE command groups
Command groups supported by the Model 6487 are listed in Table D-6. Common commands and SCPI commands are not included in this list.
Table D-6
IEEE command groups
HANDSHAKE COMMAND GROUP
NDAC = NOT DATA ACCEPTED
NRFD = NOT READY FOR DATA
DAV = DATA VALID
UNIVERSAL COMMAND GROUP
ATN = ATTENTION
DCL = DEVICE CLEAR
IFC = INTERFACE CLEAR
REN = REMOTE ENABLE
SPD = SERIAL POLL DISABLE
SPE = SERIAL POLL ENABLE
ADDRESS COMMAND GROUP
LISTEN

TALK

LAG = LISTEN ADDRESS GROUP
MLA = MY LISTEN ADDRESS
UNL = UNLISTEN
TAG = TALK ADDRESS GROUP
MTA = MY TALK ADDRESS
UNT = UNTALK
OTA = OTHER TALK ADDRESS
ADDRESSED COMMAND GROUP
ACG = ADDRESSED COMMAND GROUP
GTL = GO TO LOCAL
SDC = SELECTIVE DEVICE CLEAR
STATUS COMMAND GROUP
RQS = REQUEST SERVICE
SRQ = SERIAL POLL REQUEST
STB = STATUS BYTE
EOI = END OF IDENTIFY

D-14

IEEE-488 Bus Overview

Model 6487 Reference Manual

Interface function codes
The interface function codes, which are part of the IEEE-488 standards, define an instrument’s ability to support various interface functions and should not be confused with programming commands found elsewhere in this manual. The interface function codes for the
Model 6487 are listed in Table D-7.
Table D-7
Model 6487 interface function codes
Code
SH1
AH1
T5
L4
SR1
RL1
PP0
DC1
DT1
C0
E1
TE0
LE0

Interface function
Source Handshake capability
Acceptor Handshake capability
Talker (basic talker, talk-only, serial poll, unaddressed to talk on LAG)
Listener (basic listener, unaddressed to listen on TAG)
Service Request capability
Remote/Local capability
No Parallel Poll capability
Device Clear capability
Device Trigger capability
No Controller capability
Open collector bus drivers
No Extended Talker capability
No Extended Listener capability

The codes define Model 6487 capabilities as follows:
SH (Source Handshake Function) — SH1 defines the ability of the instrument to initiate
the transfer of message/data over the data bus.
AH (Acceptor Handshake Function) — AH1 defines the ability of the instrument to
guarantee proper reception of message/data transmitted over the data bus.
T (Talker Function) — The ability of the instrument to send data over the bus to other
devices is provided by the T function. Instrument talker capabilities (T5) exist only after
the instrument has been addressed to talk.
L (Listener Function) — The ability for the instrument to receive device-dependent data
over the bus from other devices is provided by the L function. Listener capabilities (L4) of
the instrument exist only after it has been addressed to listen.
SR (Service Request Function) — SR1 defines the ability of the instrument to request
service from the controller.
RL (Remote-Local Function) — RL1 defines the ability of the instrument to be placed in
the remote or local modes.

Model 6487 Reference Manual

IEEE-488 Bus Overview

D-15

E (Bus Driver Type) — The instrument has open-collector bus drivers (E1).
TE (Extended Talker Function) — The instrument does not have extended talker capabilities (TE0).
LE (Extended Listener Function) — The instrument does not have extended listener
capabilities (LE0).

IEEE-488 and SCPI
Conformance Information
•

GPIB 488.1 Protocol – This section introduces the GPIB 488.1 protocol.

•

Selecting the 488.1 protocol – This section describes how to select the 488.1
protocol.

•

Protocol differences – This section covers the differences between the 488.1 protocol and the SCPI protocol.

E-2

IEEE-488 and SCPI Conformance Information

Model 6487 Reference Manual

Introduction
The IEEE-488.2 standard requires specific information about how the Model 6487 implements the standard. Paragraph 4.9 of the IEEE-488.2 standard (Std 488.2-1987) lists the
documentation requirements. Table E-1 provides a summary of the requirements and provides the information or references the manual for that information. Table E-2 lists the
coupled commands used by the Model 6487.
The Model 6487 complies with SCPI version 1996.0. Table 14-1 through Table 14-9 list
the SCPI confirmed commands and the non-SCPI commands implemented by the
Model 6487.
Table E-1
IEEE-488 documentation requirements
Requirements
(1)
(2)
(3)
(4)
(5)
(a)
(b)
(c)
(d)
(e)
(6)

IEEE-488 Interface Function Codes.
Behavior of 6487 when the address is set outside the
range 0-30.
Behavior of 6487 when valid address is entered.
Power-On Setup Conditions.
Message Exchange Options:
Input buffer size.
Queries that return more than one response message
unit.
Queries that generate a response when parsed.
Queries that generate a response when read.
Coupled commands.
Functional elements required for SCPI commands.

(7)
Buffer size limitations for block data.
(8)
(9)
(10)
(11)
(12)
(13)
(14)

Syntax restrictions.
Response syntax for every query command.
Device-to-device message transfer that does not follow
rules of the standard.
Block data response size.
Common Commands implemented by 6487.
Calibration query information.
Trigger macro for *DDT.

Description or Reference
See Appendix D.
Cannot enter an invalid address.
Address changes and bus resets.
Determine by :SYSTem:POSetup
(Section 14).
2048 bytes.
None.
All queries (Common Commands and
SCPI).
None.
See Table E-2.
Contained in SCPI command
subsystems tables (see Table 14-1
through Table 14-9).
Block display messages: 12 characters
max.
See Programming Syntax in Section 9.
See Programming Syntax in Section 9.
None.
See Display Subsystem in Section 13.
See Common Commands in Section 11.
Appendix F.
Not applicable.

Model 6487 Reference Manual

IEEE-488 and SCPI Conformance Information

E-3

Table E-1 (cont.)
IEEE-488 documentation requirements
Requirements
(15)
(16)
(17)
(18)
(19)
(20)
(21)
(22)

Macro information.
Response to *IDN (identification).
Storage area for *PUD and *PUD?
Resource description for *RDT and *RDT?
Effects of *RST, *RCL, and *SAV.
*TST information.
Status register structure.
Sequential or overlapped commands.

(23)

Operation complete messages.

Description or Reference
Not applicable.
See Common Commands in Section 11.
Not applicable.
Not applicable.
See Common Commands in Section 11.
See Common Commands in Section 11.
See Status Structure in Section 10.
All are sequential except :INIT which is
overlapped.
*OPC, *OPC?, and *WAI; see
Common Commands in Section 11.

Table E-2
Coupled commands
Sending

Changes

CALC2:NULL:ACQ

CALC2:NULL:OFFS

Acquired value

TRAC:POIN
TRAC:CLE

TRAC:FEED:CONT
TRAC:FEED:CONT TRAC:CLE

NEV
NEV

GPIB 488.1 Protocol
The Model 6487 supports two GPIB protocols: SCPI (488.2) and 488.1. The 488.1 protocol is included to significantly increase speed over the GPIB.
When using the 488.1 protocol, throughput is enhanced up to 10 times for data sent to the
6487 (command messages) and up to 20 times for data returned by the Picoammeter
(response messages). The speed of readings sent over the GPIB is also increased.
klqb

With the 488.1 protocol selected, you will still use SCPI commands to program
the Model 6487. Operation differences between the two protocols are discussed
in this appendix.

E-4

IEEE-488 and SCPI Conformance Information

Model 6487 Reference Manual

Selecting the 488.1 protocol
Perform the following steps to select the 488.1 protocol:
klqb

1.
2.

3.
4.
5.
6.

The Model 6487 must be set up to be remotely controlled over the GPIB to select
the 488.1 protocol. SCPI language is the only language available over the
RS-232 bus. To setup the M odel 6487 to use GPIB from the local measurement
mode:
•

Press the COMM button.

•

Using the RANGE keys, select GPIB.

•

Press Enter to complete the change.

Press CONFIG (CONFIGURE: will be displayed).
Press COMM to access the communications menu. If a BAUD is displayed flashing, the 6487 is configured to use the RS-232 bus. See the Note above and change
to control over the GPIB.
Scroll using a RANGE key until LANG is displayed.
Press the right cursor key to place the cursor on the currently selected language
(either DDC, SCPI, or 488.1 will be flashing).
Scroll using a RANGE key until 488.1 is displayed. To change back to 488.2, scroll
to the SCPI menu item.
Press ENTER to save the change.

When switching between the SCPI protocol, DDC protocol, and 488.1 protocol, the
instrument resets. The GPIB protocol setting is saved in EEPROM and the unit will power
up with that selected protocol.
The GPIB protocol cannot be changed over the bus. However, there is a query command to
determine the presently selected protocol. When the 488.1 protocol is selected, the message exchange protocol (MEP) disables. Therefore, if you use the following query to
request the state of MEP, you will know which protocol is enabled:
:SYSTem:MEP[:STATe]?
If a “1” is returned, MEP is enabled and the SCPI protocol is selected. A “0” indicates that
MEP is disabled and the 488.1 protocol is enabled. To summarize:
1 = SCPI protocol
0 = 488.1 protocol

Model 6487 Reference Manual

IEEE-488 and SCPI Conformance Information

E-5

Protocol differences
The following information covers the differences between the 488.1 protocol and the SCPI
protocol.

Message exchange protocol (MEP)
When the 488.1 protocol is selected, the MEP is disabled to speed up GPIB operation.
The following guidelines/limitations must be followed when using the 488.1 protocol:
•

If a query is sent, it must be the only command on the line (this limitation also
means no multiple queries can be sent). Otherwise, full SCPI command syntax is
still supported including long-form and short form commands, multiple commands, and MIN/MAX/DEF parameter definitions.
For example, the following command strings are invalid:
:CURR:RANG .020; *OPC?
:CURR:RANG?;: READ?
:READ?;:READ?
The following strings are valid:
curr:nplc 1.0;:curr:rang min
:CURR:RANG? MAX
:READ?

•
•

When a query is sent, either the data must be read back or a Device Clear (DCL) or
Interface Clear (IFC) must be performed to reset the query.
When sending a command or query, do not attempt to read data from the
Model 6487 until the terminator has been sent (usually Line Feed with EOI).
Otherwise, a DCL or IFC must be sent to reset the input parser.
When receiving data, all data, up to and including the terminator (LF with EOI),
must be accepted. Otherwise, a DCL or IFC must be sent to reset the output task.
Empty command strings (terminator only) should not be sent.

Using SCPI-based programs
In general, an existing SCPI-based program will run properly and faster in the 488.1 protocol as long as it meets the above guidelines and limitations.

E-6

IEEE-488 and SCPI Conformance Information

Model 6487 Reference Manual

NRFD hold-off
*OPC, *OPC?, and *WAI are still functional but are not needed for the 488.1 protocol.
When sending commands, the GPIB is automatically held off when it detects a terminator.
The hold-off is released when all the commands have finished executing or if there is some
parser or command error. An exception is an initiate command, which releases the hold-off
immediately and does not wait for all of the readings to be acquired. This immediate
release of bus hold-off is done to support GET, SDC, IFC, *TRG, *RCL, *RST,
SYSTem:PRESet, and ABORt during data acquisition.

NDAC hold-off
NDAC hold-off is included with the GPIB 488.1 protocol mode to allow a single instrument to hold off all others on the bus until it is finished executing a command. The following command controls NDAC hold-off:
SYSTem:MEP:HOLDoff ON | OFF
The default is OFF, but NRFD hold-off will still be enabled and will prevent an instrument
from accepting further commands. See Figure E-1 for the complete IEEE-488 handshake
sequence.
Figure E-1
IEEE-488 handshake sequence
DATA

SOURCE

DAV

SOURCE
VALID
ALL READY

ACCEPTOR

NRFD
ALL ACCEPTED
NDAC

ACCEPTOR

Model 6487 Reference Manual

IEEE-488 and SCPI Conformance Information

E-7

Trigger-on-talk
Trigger-on-talk functionality has been added for the 488.1 protocol. If a query has not
been received by the instrument, the Model 6487 will automatically assume a READ?
command has been sent when it is addressed to talk. This technique increases GPIB speed
by decreasing the transmission and parser times for the command.
Trigger-on-talk is extremely useful in the single-shot reading mode (*RST default) and is
the main reason for a >2x speed improvement over the SCPI protocol.
The ARM:SOUR BUS and ARM:COUN INF commands are not supported by READ?
with the 488.1 protocol selected. If you send one of these commands, a DCL or IFC may
be required to reset the GPIB.

Message available
The MAV (message available) bit in the Serial Poll byte will be set when the query is finished being processed, not when there is data available in the output buffer (as with the
SCPI protocol). For the 488.1 protocol, output data will not be formatted until the first
request for data is received. This delay may cause unexpected time-outs when using SRQ
on MAV for queries that take a long time to execute.

General operation notes
•

•

•
•

The TALK, LSTN, and SRQ annunciators are not functional in the 488.1 protocol.
This speeds up data throughput greatly. The REM annunciator still operates since it
is critical to fundamental GPIB operation.
If the unit is in REMote, the GTL command may not put the Model 6487 into the
local mode. Only the front panel LOCAL key is guaranteed to operate, if not in
local lockout (LLO). GTL will still disable LLO.
IEEE-488 bus commands and features (GET, IFC, SDC, DCL, LLO, Serial Poll,
and SRQ) are still fully supported.
Multiple TALKs on the same query are supported as in the SCPI protocol. This feature is useful when reading back long ASCII strings.

E-8

IEEE-488 and SCPI Conformance Information

Model 6487 Reference Manual

SRQ when buffer fills with 200 readings
The following QuickBasic program (Figure E-2) will store 200 readings in the buffer.
When the buffer fills to the set amount (200 readings), an SRQ will occur and a message
will be displayed on the computer to indicate the event.
Figure E-2
Program example
' $INLCUDE: 'ieeeqb.bi'
CLS
CONST addr = 22

'Clear PC output screen.
'Set instrument address.

'
' Init GPIB
'
CALL
CALL
CALL
CALL
CALL
CALL
CALL
CALL
CALL
CALL
CALL
CALL
CALL
CALL

initialize(21, 0)
transmit("unt unl listen " + STR$(addr) + " sdc unl", status%)'Restore *rst defaults
send(addr, "*rst", status%)
'Send Device Clear.
send(addr, "trac:cle", status%)
'Clear buffer.
send(addr, "trig:coun 200", status%)
'200 trigger count.
send(addr, "trac:poin 200", status%)
'Set buffer size to 200.
send(addr, "trac:feed:cont next", status%)
'Enable buffer.
send(addr, "stat:pres", status%)
'Reset measure enable bits.
send(addr, "*cls", status%)
'Clear all event registers.
send(addr, "stat:meas:enab 512", status%)
'Enable buffer bit B9.
send(addr, "*ese 0", status%)
'Disable standard events.
send(addr, "*sre 1", status%)
'Enable measurement events.
send(addr, "syst:zch off", status%)
'Disable zero check.
send(addr, "init", status%)
'Start measurement/store process.

WAITSRQ:
WHILE srq = 0:WEND
CALL spoll(addr, poll%, status%)
CALL send(addr, "*cls", status%)
PRINT "BUFFER FULL"
END

'Wait for GPIB SRQ line to go true.
'Clear rqs/mss bit in status bit
'register.
'Clear all event registers.
'Display buffer full message.

Remote Calibration
•

Calibration commands — Summarizes those commands necessary to calibrate
the Model 6487 by remote.

•

Remote calibration overview — Gives an overview of the basic procedure for
calibrating the Model 6487 via remote.

F-2

Remote Calibration

Model 6487 Reference Manual

Introduction
This appendix contains a summary of Model 6487 remote calibration commands and a
basic remote calibration procedure. See Section 16 for complete calibration information.

Calibration commands
Table F-1 summarizes Model 6487 remote calibration commands.
Table F-1
Calibration commands
Command
:CALibration
:PROTected
:CODE ''
:CODE?
:LOCK
:LOCK?
:SENSe
:DATA?
:VSOurce
:NFSCale
:NFSValue
:ZERO
:ZVALue
:PFSCale
:PFSValue
:SOURce
:DATA?
:SAVE
:DATE
:DATE?
:NDUE
:NDUE?
:COUNt?
:UNPRotected
:VOFFset

Description
Calibration subsystem.
Commands protected by code/password.
Eight character code/password used to enable or unlock calibration.
(Default: KI006487.)
Calibration code query.
Lock out further calibration.
Return 1 if calibration is locked, 0 otherwise.
Calibrate active current range.
Query measurement cal constants.
Voltage source calibration commands:
Turn on source, set it to negative full scale for present source range.
Calibrate negative full scale using DMM reading.
Set source output to 0V and turn on output.
Calibrate source zero using DMM reading.
Turn on source, set it to positive full scale for present source range.
Calibrate positive full scale using DMM reading.
Path to query source calibration constants.
Query constants for present source range. Three values are returned:
Vnegative, Vpositive, and Vzero.
Save all calibration data to non-volatile memory.
Year, Month, Day when cal was last performed.
Query last cal date.
Year, Month, Day when 6487 is due for re-cal.
Query cal due date.
Returns how many times 6487 has been calibrated.
Commands not protected by code/password.
Voltage offset correction.

Model 6487 Reference Manual

Remote Calibration

F-3

Remote calibration overview
The steps below outline the general procedure for calibrating the Model 6487 using
remote commands. Refer to Section 16 for details on calibration steps, calibration points,
and test equipment connections.
1.

Send the following command to unlock calibration:
:CAL:PROT:CODE 'KI006487'
Note that the above command uses the factory default code.
Perform voltage offset correction by sending the following command:
:CAL:UNPR:VOFF
Be sure a triax shielding cap is connected to the INPUT jack before sending the
above command.
Send the appropriate command to select the current range to be calibrated. For
example, the following command selects the 20mA range:
:SENS:CURR:RANG 2e-2
Make appropriate connections (see Figure 16-1 and Figure 16-2), then send the
commands for each calibration point for the selected function and range. For example, send the following commands for the 20mA range:
:CAL:PROT:SENS 0
:CAL:PROT:SENS 2e-2
:CAL:PROT:SENS –2e-2
Repeat steps 3 and 4 for each range (Table F-2).

t^okfkd

7.
8.

Hazardous voltages will be present during voltage source calibration
steps. Use care to avoid a shock hazard. The interlock must be closed
to calibrate the 50V and 500V ranges. See Section 2 for interlock
information.

Be sure the DMM is connected to the Model 6487 voltage source terminals (see
Figure 16-3), then send the commands for each calibration point for the selected
range, as summarized in Table F-3. Be sure to include the actual DMM reading for
each step where shown.
Repeat step 6 for each voltage source range.
After all current and voltage source ranges are calibrated, send the commands to
program the calibration dates; for example:
:CAL:PROT:DATE 2002,12,15
:CAL:PROT:NDUE 2003,12,15
Finally, send the following commands to save calibration constants and then lock
out calibration:
:CAL:PROT:SAVE
:CAL:PROT:LOCK

F-4

Remote Calibration

Model 6487 Reference Manual

Table F-2
Current calibration commands by range
Range

Commands*

2nA

:SENS:CURR:RANG 2e-9
:CAL:PROT:SENS 0
:CAL:PROT:SENS 2e-9
:CAL:PROT:SENS –2e-9

20nA

:SENS:CURR:RANG 2e-8
:CAL:PROT:SENS 0
:CAL:PROT:SENS 2e-8
:CAL:PROT:SENS –2e-8

200nA

:SENS:CURR:RANG 2e-7
:CAL:PROT:SENS 0
:CAL:PROT:SENS 2e-7
:CAL:PROT:SENS –2e-7

2μA

:SENS:CURR:RANG 2e-6
:CAL:PROT:SENS 0
:CAL:PROT:SENS 2e-6
:CAL:PROT:SENS –2e-6

20μA

:SENS:CURR:RANG 2e-5
:CAL:PROT:SENS 0
:CAL:PROT:SENS 2e-5
:CAL:PROT:SENS –2e-5

200μA

:SENS:CURR:RANG 2e-4
:CAL:PROT:SENS 0
:CAL:PROT:SENS 2e-4
:CAL:PROT:SENS –2e-4

2mA

:SENS:CURR:RANG 2e-3
:CAL:PROT:SENS 0
:CAL:PROT:SENS 2e-3
:CAL:PROT:SENS –2e-3

20mA

:SENS:CURR:RANG 2e-2
:CAL:PROT:SENS 0
:CAL:PROT:SENS 2e-2
:CAL:PROT:SENS –2e-2

* Full-scale calibration values for 2nA to 2μA ranges should be calculated from calibrator voltages and standard resistance values. (See
Section 16.) Values for 20μA to 20mA ranges can be used as shown.

Model 6487 Reference Manual

Remote Calibration

Table F-3
Voltage source calibration commands by range
Range

Commands*

10V

:SOUR1:VOLT:RANG 10
:CAL:PROT:VSO:NFSC
:CAL:PROT:VSO:NFSV
:CAL:PROT:VSO:ZERO
:CAL:PROT:VSO:ZVAL
:CAL:PROT:VSO:PFSC
:CAL:PROT:VSO:PFSV

50V

:SOUR1:VOLT:RANG 50
:CAL:PROT:VSO:NFSC
:CAL:PROT:VSO:NFSV
:CAL:PROT:VSO:ZERO
:CAL:PROT:VSO:ZVAL
:CAL:PROT:VSO:PFSC
:CAL:PROT:VSO:PFSV

500V

:SOUR1:VOLT:RANG 500
:CAL:PROT:VSO:NFSC
:CAL:PROT:VSO:NFSV
:CAL:PROT:VSO:ZERO
:CAL:PROT:VSO:ZVAL
:CAL:PROT:VSO:PFSC
:CAL:PROT:VSO:PFSV

* Include from output voltage generated by previous step.
For example, :CAL:PROT:VSO:NFSV value is generated by
:CAL:PROT:VSO:NFSC command.

F-5

Applications Guide
•

Measurement considerations — Covers measurement considerations for low current measurements including Leakage currents and guarding, Input bias current,
Voltage burden, Noise and source impedance, Electrostatic interference and shielding, and Making connections.

•

Applications — Covers applications to measure Diode leakage current, Capacitor
leakage current, Measuring high resistance, Cable insulation resistance, Surface
insulation resistance (SIR), Photodiode characterization prior to dicing, Focused
ion beam applications and Using switching systems to measure multiple current
sources.

G-2

Applications Guide

Model 6487 Reference Manual

Measurement considerations
Some considerations for making accurate amps measurements are summarized as follows.
Additional measurement considerations are covered in Appendix C of the Model 6487
User’s Manual. For comprehensive information on precision measurements, refer to the
Low Level Measurements handbook, which is available from Keithley Instruments.
It is critical that the picoammeter perform the measurement without interfering with the
flow of current in the circuit, possibly affecting operation or inducing additional errors.
Voltage burden is the terminal voltage of a picoammeter and ideally this voltage should be
zero (no resistive or offset effect). Some meters, such as DMMs, utilize a shunt resistor to
measure the voltage drop across a known resistance and a typical burden of 200mV is not
unusual.
The Keithley Model 6487 uses an alternative approach referred to as a feedback picoammeter, where the voltage burden is simply the input voltage of an operational amplifier.
Furthermore, since the input voltage of the operational amplifier is the output voltage
divided by the gain (typically 500,000) the voltage burden is in the microvolt range.

Leakage currents and guarding
Leakage currents are generated by high resistance paths between the measurements circuit
and nearby sources. These currents can considerably degrade the accuracy of low current
measurements. Some ways to reduce leakage currents are to use good quality insulators,
maintain cleanliness on the surface of insulators, reduce humidity, and use guarding.
Guarding also reduces the effect of shunt capacitance in the measurement circuit.
One way to reduce leakage currents is to use good quality insulators when building the test
circuit. The best insulator is air. If possible, use air as the insulator for the sensitive node
(the part of the circuit between the source of current and the ammeter HI input). Because
this connection must eventually be mechanically supported, good insulators should still be
used whenever it is necessary to make physical contact to the sensitive node. Some good
quality insulators are Teflon, polyethylene, and sapphire. Avoid materials such as phenolics and nylon. Refer to Keithley’s Low Level Handbook for additional information on
choosing the best insulator.
Humidity may also degrade low current measurements. The amount of water an insulator
absorbs will vary depending upon the insulator. It is best to choose an insulator on which
water vapor does not readily form a continuous film. Sometimes this is unavoidable if the
material being measured absorbs water easily, so it is best to make the measurements in an
environmentally controlled room. In some cases, an insulator may have ionic contaminants and, especially in high humidity, a spurious current may be generated.

Model 6487 Reference Manual

Applications Guide

G-3

Another way to reduce leakage currents is to use guarding. A guard is a conductor connected to a low impedance point in the circuit that is nearly at the same potential as the
high impedance lead (the sensitive node) being guarded. Guarding can isolate the highimpedance input lead of the picoammeter from leakage current due to voltage sources.
Guarding may also be necessary to prevent leakage current due to test fixturing.
Figure G-1 shows a high-megohm resistor supported on two insulators mounted in a metal
test fixture. This circuit is guarded by connecting the LO of the picoammeter to the metal
case. This will put the top of the insulator support post on the right at almost the same
potential as the bottom. The voltage difference is equal to the voltage burden of the
picoammeter. Since the top and the bottom of the insulator are at nearly the same potential, no significant current will flow through it and nearly all the current from the device
under test will flow through the picoammeter.
Figure G-1
Guarding to reduce leakage currents
Metal
Shield

Test Fixture

Insulators

6487
V-Source

+ HI

- LO

DUT

HI
Measured
Current

6487
Picoammeter

Equivalent Circuit

Input bias current
An ideal picoammeter would read 0A with an open input. In practice, however, ammeters
do have some current that flows when the input is open. This current is known as the input
bias (offset) current. It should be noted that this current emanates from points within the
ammeter and flows through the internal ammeter circuitry, but it does not flow through the
DUT. The input bias current for the Model 6487 is included in the offset portion of the
accuracy specification.

G-4

Applications Guide

Model 6487 Reference Manual

Voltage burden
The input resistance of the picoammeter causes a small voltage drop across the input terminals. This voltage is known as the voltage burden. If the voltage burden is large in relation to the voltage of the measured circuit, then significant measurement errors will occur.
Refer to Figure G-2 to see how voltage burden affects current measurements. Assume VS
is 5mV and RS is 5kΩ to configure a 1μA current source (5mV/5kΩ = 1µA). An ideal
picoammeter with zero voltage burden would allow 1μA to flow and measure it
accurately.
In practice, however, every picoammeter has a voltage burden. If the voltage burden (VB)
is 1mV, the current that flows will be:
VS – VB
– 1mV- = 0.8μA
I M = -------------------= 5mV
-----------------------------5kΩ
RS

The 1mV voltage burden caused a 20% reduction in actual current. Percent error in a measured reading (IM) due to voltage burden can be calculated as follows:
100%
I M % error = ---------------------( V S /V B )

The voltage burden of the Model 6487 depends on the selected range (see specifications).
Voltage burden may be reduced by performing the voltage offset correction procedure.

Voltage offset correction procedure
klqb

To maintain specified operation, any time there is a substantial change in the
ambient temperature, the voltage offset procedure should be performed and
saved.
Press the MENU key to display the following:
CAL: VOFFSET

Press ENTER. The instrument will prompt as follows:
INPUT CAP

4.
5.
klqb

It is not necessary to disconnect signal cables from the Model 6487, but it is recommended that signal currents be reduced to zero if possible. During the calibration,
the input impedance will be 3.5MΩ, therefore continued signal currents will
present a corresponding voltage to the DUT.
Press ENTER to complete offset voltage calibration.
Press EXIT to return to normal display.
Like the other calibration procedures, this calibration is not permanently stored
until CAL:UNLOCK and CAL:SAVE have been performed. Saving the results of
this calibration at a temperature other than that at which the Model 6487 will be
used will adversely affect measurement results.

Model 6487 Reference Manual

Applications Guide

G-5

Figure G-2
Voltage burden considerations
Rs

6487
V-Source

+
Vs

(Voltage
Burden)
IM =

VS - VB
RS

Model of 6487 Picoammeter
Input Characteristics Before
Voltage Offset Correction

Noise and source impedance
Noise can seriously affect sensitive current measurements. The following paragraphs discuss how source resistance and input capacitance affect noise performance.

Source resistance
The source resistance of the DUT will affect the noise performance of current measurements. As the source resistance is reduced, the noise gain of the picoammeter will
increase, as we will now discuss.
Figure G-3 shows a simplified model of the feedback picoammeter. RS and CS represent
the source resistance and source capacitance, VS is the source voltage, and VNOISE is the
noise voltage. Finally, RF and CF are the feedback resistance and capacitance respectively.
The source noise gain of the circuit can be given by the following equation:
Output V NOISE = Input V NOISE ( 1 + R F /R S )

Note that as RS decreases in value, the output noise increases. For example, when RF = RS,
the input noise is multiplied by a factor of two. Since decreasing the source resistance can
have a detrimental effect on noise performance, there are usually minimum recommended
source resistance values based on measurement range. Table G-1 summarizes minimum
recommended source resistance values for various measurement ranges. Note that the recommended source resistance varies by measurement range because the RF value also
depends on the measurement range.

G-6

Applications Guide

Model 6487 Reference Manual

Table G-1
Minimum recommended source resistance values
Range
2nA, 20nA
200nA, 2µA
20µA, 200µA
2mA, 20mA

Minimum recommended source resistance
1 MΩ to 1 GΩ
10 kΩ to 10 MΩ
100Ω to 100 kΩ
10Ω to 1kΩ

Figure G-3
Simplified model of a feedback picoammeter
CF
RF

CS
ZS

+
VO
Vnoise

Current
Source

6487
Picoammeter

Source capacitance
DUT source capacitance will also affect the noise performance of the Model 6487 picoammeter. In general, as source capacitance increases, the noise also increases. To see how
changes in source capacitance can affect noise gain, again refer to the simplified picoammeter model in Figure G-3. The elements of interest for this discussion are the source
capacitance (CS) and the feedback capacitance (CF). Taking into account the capacitive
reactance of these two elements, the previous noise gain formula must be modified as
follows:
Output V NOISE = Input V NOISE ( 1 + Z F /Z S )

Model 6487 Reference Manual

Applications Guide

G-7

Here, ZF represents the feedback impedance made up of CF and RF, while ZS is the source
impedance formed by RS and CS. Furthermore,
RF
Z F = -----------------------------------------------2
[ ( 2πfR F C F ) + 1 ]

and,
RS
Z S = -----------------------------------------------2
[ ( 2πfR S C S ) + 1 ]

Note that as CS increases in value, ZS decreases in value, thereby increasing the noise gain.
Again, at the point where ZS = ZF, the input noise is amplified by a factor of two.
The maximum value of source capacitance (CS) for the lower ranges of the Model 6487
picoammeter is 10,000pF. You can, however, usually measure at higher source capacitance
values by inserting a resistor in series with the picoammeter input, but remember that any
series resistance will increase the voltage burden by IIN • RSERIES. For example, the range
of resistance listed in Table G-1 will result in voltage burden values in range of 2mV to
2V. A useful alternative to a series resistor is a series diode or two diodes in parallel
back-to-back. The diodes can be small-signal types and should be in a light-tight
enclosure.

Electrostatic interference and shielding
Electrostatic interference is probably the most common source of error when making low
current measurements. Electrostatic coupling or interference occurs when an electrically
charged object is brought near an uncharged object. At low impedance levels, the effect of
the interference are not noticeable because the charge dissipates rapidly. However, high
resistance materials do not allow the charge to decay quickly, which may result in unstable
measurements. The erroneous readings may be due to either DC or AC electrostatic fields,
so electrostatic shielding will help minimize the effects of these fields.
DC fields can produce noisy readings or undetected errors. These fields can be detected
when movement near an experiment (such as the movement of the person operating the
instrument or others in the immediate vicinity) causes fluctuations on the picoammeter's
display. To perform a quick check for interference, place a piece of charged plastic, such
as a comb, near the circuit. A large change in the meter reading indicates insufficient
shielding.
AC fields can be equally troublesome. These are caused most often by power lines and RF
fields. If the AC voltage at the input is large, part of this signal is rectified, producing an
error in the DC signal being measured. This can be checked by observing the analog output of the picoammeter with an oscilloscope. A clipped waveform indicates a need to
improve electrostatic shielding.

G-8

Applications Guide

Model 6487 Reference Manual

Figure G-4 shows an example of AC electrostatic coupling. An electrostatic voltage
source in the vicinity of a conductor, such as a cable or trace on a PC board, generates a
current proportional to the rate of change of the voltage and of the coupling capacitance.
This current can be calculated with the following equation:
dC
dV
i = C ------- + V ------dt
d

Figure G-4
Electrostatic coupling
i
Ground-referenced
signal conductor

C
Coupling
capacitance
V

Electrostatic
voltage source

i = C dV + V dC
dt
dt

For example, two conductors, each with lcm2 area and spaced lcm apart by air, will have
almost 0.1pF of capacitance. With a voltage difference of 100V and a vibration causing a
change of capacitance of 0.01pF/second (a 10% fluctuation), a current of 1pA will be
generated.
To reduce the effects of the fields, a shield can be built to enclose the circuit being measured. The easiest type of shield to make is a simple metal box or meshed screen that
encloses the test circuit. Shielded boxes are also available commercially.
Figure G-5 illustrates an example of shielding. Made from a conductive material, the
shield is always connected to the low impedance input of the electrometer or picoammeter.
If circuit low is floating above ground, observe special safety precautions to prevent anyone from touching the shield, such as triaxial cable with the outer shield at earth potential.

Model 6487 Reference Manual

Applications Guide

G-9

Figure G-5
Shielding a high impedance device
Metal
Shield
High Impedance
DUT

6487
V-Source

+ HI

Measured
Current
(I)

- LO

6487
Picoammeter

Equivalent Circuit

The cabling in the circuit also requires shielding. Capacitive coupling between an electrostatic noise source and the signal conductors or cables can be greatly reduced by surrounding those conductors with a grounded metal shield (Figure G-6). With this shield in place,
the noise current generated by the electrostatic voltage source and the coupling capacitance flows through the shield to ground rather than through the signal conductors.
Figure G-6
Electrostatic shielding
Shield

Ground-referenced
signal conductor
Ground

Shield-to-cable
capacitance

Noise
current
V

Source-to-shield
capacitance

Electrostatic
voltage source

G-10

Applications Guide

Model 6487 Reference Manual

To summarize, error currents due to electrostatic coupling can be minimized by following
these guidelines:
•
•
•

Keep all charged objects (including people) and conductors away from sensitive
areas of the test circuit.
Avoid movement and vibration near the test area.
When measuring currents <10nA, shield the device under test by surrounding it
with a metal enclosure and connect the enclosure electrically to the test circuit
common terminal.

Shielding vs. Guarding
Shielding usually implies the use of a metallic enclosure to prevent electrostatic interference from affecting a high impedance circuit. Guarding implies the use of an added low
impedance conductor, maintained at the same potential as the high impedance circuit,
which will intercept any interfering voltage or current. A guard does not necessarily provide shielding. (“Leakage currents and guarding,” page G-2.)

Making connections
To avoid measurement errors, it is critical to make proper connections from the picoammeter to the device under test. To make a proper connection, always connect the high
resistance terminal of the meter to the highest resistance point of the circuit under
test.
Figure G-7 shows a picoammeter connected to a current source that consists of a voltage
source in series with a resistor. An AC powered voltage source usually has a significant
level (often several volts) of line frequency common mode voltage.
Figure G-7
Connecting the HI terminal (picoammeter) to high resistance
Current Source

R
+

6487
Picoammeter

A
LO

Model 6487 Reference Manual

Applications Guide

G-11

As shown in Figure G-8, this will cause a current (i) to flow through the low to ground
capacitance of the picoammeter (A). Picoammeter HI is connected to the higher resistance
side of the circuit being measured, the “R” side of this current source. This circuit is connected properly, so this current does not flow through the picoammeter and, therefore,
does not cause any measurement errors.
Figure G-8
Proper connection
Current Source

6487
Picoammeter

However, when the HI of the picoammeter is connected to the low impedance side of the
DUT, this AC current (i) flows through the picoammeter (A) as illustrated in Figure G-9.
This current may affect the measurement accuracy, especially at low signal levels.

G-12

Applications Guide

Model 6487 Reference Manual

Figure G-9
Improper connection

Current Source

6487
Picoammeter

Refer to “Connection fundamentals,” page 2-2 for details on appropriate types of cabling
and connectors to use when making picoammeter measurements.

Typical range change transients
During a range change, a picoammeter cannot perfectly maintain its voltage burden specification. When a range change occurs, the picoammeter will momentarily become a
current-limited voltage source (Figure G-10).

Model 6487 Reference Manual

Applications Guide

G-13

Figure G-10
Range change voltage transients
RF

6487
Picoammeter

V Transient

klqb

Range being
changed to:

2mA, 20mA
20μA, 200μA
200nA, 2μA
2nA, 20nA

500Ω
50kΩ
5MΩ
500MΩ

The current that can be inadvertently delivered to the DUT is limited by an
internal resistance. This internal resistance varies as the range is changed. For
example, manually up-ranging from 2μA to the 20μA range can never deliver
more than 10V/50kΩ = 200μA to the DUT. This current will be further limited
by any impedance of the DUT.

G-14

Applications Guide

Model 6487 Reference Manual

Up-range input response
Figure G-11 illustrates the type of transient voltage that can be expected when up-ranging
with a full-scale input signal (200μA signal on 200μA range, up-range to 2mA range).
Both the magnitude and duration of this voltage are reduced for lower current ranges. The
current limit imposed by the RF is also greatly reduced. The polarity depends on the polarity of the input current. Figure G-11 was measured with a positive input current.
Figure G-11
Transient Voltage

When it is necessary to up-range during auto-ranging operation, multiple ranges may be
crossed to find the correct range. The duration of the transient in Figure G-11 can be
extended in this case, but the magnitude will not increase significantly.

Model 6487 Reference Manual

Applications Guide

G-15

Down-range voltage transients are smaller
With the exception of the change from the 2mA range to the 200μA range, the down-range
voltage transient is significantly smaller than the up-range transients. Figure G-12 shows
the voltage presented at the input, measured during a change from 20μA to 2μA with a
2μA input current. The vast difference from the previous figures in voltage scale and time
scale should be noted. Note also that the current limiting resistor will be that of the 2μA
range, 100 times greater than upranging across the same boundary. The voltage transient
of the 2mA to 200μA change with a 200μA input signal is similar to the up-range
response, with the exception that the current limiting R will be 100 times greater in the
case of down-ranging.
Figure G-12
Down-range voltage transients

G-16

Applications Guide

Model 6487 Reference Manual

Steps to minimize impact of range change transients
When changing between the following range pairs (up or down), no input transients occur:
2nA and 20nA, 200nA and 2μA, 20μA and 200μA, 2mA and 20mA. This is not true when
auto-ranging upwards across these boundaries.

Run test with a fixed range
If possible, run the test within a fixed range. Choose the higher range from any of the
range pairs listed above. Alternatively, the autorange upper limit
(:RANGe:AUTO:ULIMit, see “Noise and safety shields” or “Autorange limits” in the
6487 User’s Manual) can be set so that the internal limiting resistor (RF) cannot be
reduced to the lower values. Choose the appropriate range to accommodate the maximum
current expected during normal measurements.

Down-range by starting at highest current necessary
Make use of down-ranging by starting at the highest current necessary and reducing down
to zero, the range change transients can be reduced significantly compared to up-ranging
transients.

Using protection circuitry
Using protection circuitry can greatly reduce currents and voltages presented to devices
being tested, as well as serving to protect the Model 6487 from any externally generated
transients. If using the scheme from “Noise and safety shields” in the 6487 User’s Manual,
size the external current limiting resistor such that the sum of the external resistor and the
lowest RF will limit a 10V transient to a current level acceptable to the DUT.

Reduce up-ranging transient
If the application requires that up-ranging be used, and when the transient through the
internal limiting resistor RF would damage the DUT, the up-ranging transient can be
reduced greatly by reducing the input current to <10% of the present range before forcing
the range change up (manual or fixed-ranging over the bus). This can be true when running
the first I-V curve on devices whose characteristics are not yet known, so that sweeping
from low current towards high current is the only way to avoid exceeding a maximum current through the device.

Model 6487 Reference Manual

Applications Guide

G-17

Zero check on / off response
Figure G-13 shows the transient that can be expected from input HI to LO during a change
in the zero check mode with no input current. The transition is similar for entering and
leaving zero check. For current ranges 2μA and below, the magnitude of the response is
not as large, but similar in duration. As with range change transients, the zero check transient is presented through an internal impedance which will limit the resulting current
through the DUT (Table G-2). If there is an input current while in zero check, the input
voltage will depend on the current and the zero check input impedance for the specific
range.
Figure G-13
Zero check transient

Table G-2
Internal impedance for zero check transient
Range Zcheck

Transient
impedance

2mA,20mA

500Ω

20μA,200μA

50kΩ

200nA,2μA

3.5MΩ

2nA,20nA

11MΩ

G-18

Applications Guide

Model 6487 Reference Manual

Applications
Diode leakage current
Figure G-14 shows how to measure the leakage current for a diode. By sourcing a positive
voltage, the leakage current through the diode will be measured. Note that if you source a
negative voltage, you will forward bias the diode. Resistor R is used to limit current in the
event that the diode shorts out or it becomes forward biased. Select a value of R that will
limit current to 20mA or less.
A profile for leakage current can be developed by measuring current at various voltage
levels. For example, program the voltage source to sweep voltage from 1 to 10V in 1V
steps. The Model 6487 performs a current measurement on each voltage step. To ensure
that the voltage is settled before each current measurement, you can program the
Model 6487 for a delay. For example, if you program the Model 6487 for a one second
delay, each measurement will be performed after the voltage step is allowed to settle for
one second. The current measurements are stored in the buffer.
klqb

Buffer and voltage sweep operation are covered in Section 6.

Figure G-14
Connections; diode leakage current test
Metal
Shield
R

6487
V-Source

Diode
HI

+ HI

A
- LO

6487
Picoammeter

LO
Equivalent Circuit

klqb

The details on “Typical range change transients,” page G-12 may be particularly relevant to this application

Model 6487 Reference Manual

Applications Guide

G-19

Capacitor leakage current
Figure G-15 shows how to measure the leakage current for a capacitor. The magnitude of
the leakage is dependent on the type of dielectric and the applied voltage.
A resistor and a diode are used to limit noise for the measurement. The resistor limits the
current in case the capacitor becomes shorted, and it also offsets the effects of decreasing
capacitive reactance with increasing frequency, which affects picoammeter noise performance (see “Source capacitance,” page G-6). A good starting point is to choose a resistance value that results in an RC time constant of 0.5 to 2 seconds. (See Table G-1 for
minimum recommended resistance values based on measurement range.) The diode acts
like a variable resistance, low while the capacitor is charging, and much higher when the
capacitor is fully charged. As a result, the resistance value can be significantly smaller.
Also damping may help to reduce noise (see “Damping,” page 4-8).
For this test, a fixed bias voltage is to be applied to the capacitor for a specified time to
allow the capacitor to fully charge (current decays exponentially with time). The leakage
current is then measured. After the measurement, the voltage source is set to output 0V for
a specified time to allow the capacitor to discharge. Note that measurements with the voltage source in the high-impedance state (from interlock opening) might have high noise
pickup caused by an unshielded voltage source HI terminal.
Figure G-15
Connections; capacitor leakage current test
Metal
Shield

6487
V-Source

+ HI

A
- LO

6487
Picoammeter

Equivalent Circuit

Measuring high resistance
The Model 6487 can be used to make high resistance (>1GΩ) measurements using the
built-in voltage source. The alternating voltage ohms mode (Section 3) can be used to
improve accuracy and repeatability of very high resistance measurements. High resistance
measurement applications include insulation resistance testing and resistivity measurements of insulators.

G-20

Applications Guide

Model 6487 Reference Manual

To measure high resistance, the internal voltage source is placed in series with the
unknown resistance and the picoammeter. Since the voltage drop across the picoammeter
is negligible, essentially all the voltage appears across the unknown resistance. The resulting current is measured by the picoammeter. The resistance is then calculated and displayed using Ohm's Law:
R = V
---I

where:

V is the sourced test voltage
I is the measured current

The basic configuration for measuring high resistance using the Model 6487 Picoammeter
is shown in Figure G-16. The HI terminal of the Model 6487 picoammeter is connected to
one end of the unknown resistance (R) and the HI terminal of the internal voltage source to
the other end of the resistance. The LO terminal of the picoammeter is connected to the
LO terminal of the voltage source. Both LO terminals are also connected to earth ground.
This should be done via the ground link on the rear of the Model 6487.
Figure G-16
Measuring high resistance using the 6487
Metal
Shield
Unknown Resistance
6487
V-Source
(V)

+ HI

- LO

(R)

HI
Measured
Current

6487
Picoammeter

Equivalent Circuit

To prevent generated current due to electrostatic interference, place the unknown resistance in a shielded test fixture. The metal shield is connected to the LO terminal of the
6487.

Alternating voltage ohms measurement
To reduce measurement errors caused by background currents, use the alternating voltage
ohms measurement mode. The step voltage and time for each phase should be carefully
chosen to assure proper circuit settling, while the averaging a number of reading cycles
will improve repeatability. See “Alternating voltage ohms mode,” page 3-21 in Section 3
for details.

Model 6487 Reference Manual

Applications Guide

G-21

Cable insulation resistance
Figure G-17 shows how to measure the insulation resistance of a cable. The resistance of
the insulator between the shield and the inner conductor is being measured. The cable
sample should be kept as short as possible to minimize input capacitance to the
picoammeter.
For this test, a fixed bias voltage is applied across the insulator for a specified time to allow
the charging effects of cable capacitance to stabilize. The current is then measured. Cable
resistance (R) can then be calculated as follows:
R = V
---I

where:

V is the sourced bias voltage
I is the measured current

Figure G-17
Connections; cable insulation resistance test
Metal
Shield
Center Conductor
Cable
Shield
Equivalent Cable
Resistance (R)
6487
V-Source
(V)

+ HI

- LO

Measured
Current

A
LO

6487
Picoammeter

G-22

Applications Guide

Model 6487 Reference Manual

Surface insulation resistance (SIR)
Figure G-18 shows how to measure the insulation resistance between PC board traces.
Note that the drawing shows a “Y” test pattern for the measurement. This is a typical test
pattern for SIR tests.
A bias voltage (typically 50V) is applied to the test pattern for a specified time (typically
one second) to polarize the test pattern. The test voltage (typically 100V) is then applied
and, after a specified time (typically one second), the Model 6487 measures the current.
Surface insulation resistance can now be calculated as follows:
SIR = V
---I

where:

V is the sourced test voltage
I is the measured current

Figure G-18
Connections; surface insulation resistance test
Metal
Shield
PC Board
Test Pattern

6487
V-Source
(V)

+ HI
-

HI
Measured
Current
(I)

A
LO

Equivalent Circuit

6487
Picoammeter

Model 6487 Reference Manual

Applications Guide

G-23

Photodiode characterization prior to dicing
The Model 6487 can be used as part of a cost-effective semiconductor photodiode leakage
test system. This test characterizes the photo current under various illumination
conditions.
In addition to the Model 6487, specialized equipment is required. This equipment includes
a calibrated optical source in addition to semiconductor equipment (probe card or needle
mounts, etc.). Several Model 6487s can be connected to probe pads to provide leakage
current readings forced by the bias voltage source. As an alternative, one or more
Model 6487s could be switched through a switching mainframe and matrix switch card
arrangement to take current measurements from multiple pads.
Measuring photodiode leakage can be described in two steps:
1. Vsweep, Imeas in total darkness.
2. Vbias, Imeas in calibrated optical flux.

In the 1st step, voltage sweeps and the resulting current leakage is measured (see “Voltage
sweeps,” page 6-8). Then, a bias voltage is applied and resulting current leakage is measured while light is incrementally increased in calibrated steps. The results produce a
graph similar to Figure G-19.
Figure G-19
General photodiode leakage
General photodiode

G-24

Applications Guide

Model 6487 Reference Manual

P.I.N. (Positive Intrinsic Negative) diodes respond as shown in Figure G-20.
Figure G-20
PIN photodiode leakage
P.I.N. photodiode

In total darkness, Avalanche diodes respond as shown by the solid line in Figure G-21.
Notice the small irregularity of the curve while sweeping around 10-12V. This irregularity
is made larger under additional applied light (see dashed lines of Figure G-21).
Figure G-21
Avalanche photodiode leakage
Avalanche photodiode

LEGEND
More
Light

100
V

Model 6487 Reference Manual

Applications Guide

G-25

Connections are made to the Model 6487 through the triax input connector (located on the
rear panel) (Figure G-22) as well as the voltage source output terminals to provide the necessary bias voltage.
Figure G-22
Basic connection scheme
Calibrated Light Source
Photodiode
Pads
Probe Needles
Probe Needles

Wafer
Bias Voltage

klqb

Model 6487

The details on “Typical range change transients,” page G-12 may be particularly relevant to this application

Focused ion beam applications
Focused Ion Beam (FIB) systems have been developed to perform nanometer-scale imaging, micro machining, and mapping in the semiconductor industry. Typical applications
include mask repair, circuit modification, defect analysis, and sample preparation of sitespecific locations on integrated circuits.
FIB systems use a finely focused ion beam for imaging or for site specific sputtering or
milling. The magnitude of the beam current determines what type of operation is performed. A low beam current results in very little material being sputtered and is, therefore,
ideal for imaging applications. Utilization of high beam currents resulting in a great deal
of material being removed by sputtering, and is subsequently well suited for precision
milling operations.
Therefore, whether the application calls for imaging or a complete circuit modification,
monitoring and control of the beam current is critical to the success of the process. The ion
beam current cannot be measured directly, but requires the use of an ion detector. There
are several detectors commonly used throughout the industry including Channeltron®,
Daly, Microchannel plate, and the Faraday cup. The Faraday cup can only be used in an
analog mode and is, therefore, not as sensitive as newer current pulse devices.

G-26

Applications Guide

Model 6487 Reference Manual

The function of the detector is to develop a secondary current proportional to the current
of the primary ion beam, without interfering with the primary beam. The basic operation
of most detectors is similar; an ion from the primary beam strikes the detector and a secondary ion is generated, isolated from the primary ion stream. This current is then measured and used to control the intensity of the beam.
The secondary currents generated by the detectors are very low and require a high degree
of accuracy and measurement repeatability. Currents as low as 5 or 6pA are not uncommon; therefore, the measurement device must be capable of achieving resolutions below
1pA.
The Model 6487 is ideal for this application because it offers a wide selection of range settings spanning from 20mA to 2nA. This will result in 5-1/2 digit resolution ranging from
100nA to 10fA. Numerous ranges, and fine measurement granularity, will meet all current requirements for this application, as well as provide additional sensitivity for future
development needs.
Signal connections to the picoammeter are made using the triax connector mounted on the
rear panel. If the source on the ions is biased off ground, then the ion detector will most
likely be at ground potential. A simple coaxial vacuum feedthrough can be used to make
the connection between the detector and the picoammeter (Figure G-23).
Figure G-23
Focused Ion Beam signal connections
6487
Picoammeter
Ion
Detector
Coaxial Vacuum
Feedthrough

Using switching systems to measure multiple current sources
Refer to “External trigger example,” page 7-13.

Ion
Beam

Index

Calibration menu 16-5
Calibrator 15-4, 16-4
Calibrator voltage calculations 15-5
Capacitor leakage current G-19
Case sensitivity 9-12
Category 8-8, 8-9
Changing the calibration code 16-14
cleaning
test fixtures 2-10
tips 2-10
Clearing registers and queues 10-4
Command 3-27, 6-11
codes D-9, D-11
execution rules 9-15
path rules 9-14
words 9-10
Common 11-1
Common Commands 11-2, D-11
Compliance 3-18
Component 8-7, 8-8
Condition registers 10-15
CONFIG/LOCAL key 9-10
Configuration 1-13
Connections 2-1, 2-4, 2-5, 2-6
fundamentals 2-2
Connections for 20mA to 20mA range
calibration 16-9
Connections for 20mA to 20mA range
verification 15-8, 15-10
Connections for 2nA to 2mA range calibration
16-11, 16-13
Connections for 2nA to 2mA range verification
15-11
Connectors 2-10
Contact information 1-3
control sources 7-5
Controlling 8-13
Counters 7-7
coupling, electrostatic G-7, G-8
Current 3-2, 3-7, F-4
Current calculations 16-6
Current calibration 16-8
Current measurement accuracy 15-7
currently detected frequency 1-6

VOFFset F-2

Symbols
“Selecting and configuring an interface,” page
8-2 9-7

A
acquire method to zero correct 3-7
Additional references 1-4
Address commands D-10
Addressed multiline commands D-10
Alternating G-20
analog 2-15
Applications Guide G-1
ARM layer 7-8
configuration menu 8-17
Autoranging 4-2
limits 4-3
Autozero 3-3
autozero 3-25
Avalanche photo diode leakage G-24
avoiding measurement errors G-10

B
Baseline Suppression (Rel) C-9
Basic 2-4, 2-5, 2-6, 3-2
connection scheme G-25
connections to DUT 2-4
Baud rate 9-16
Binning 8-5
Buffer 3-26, 6-1, 6-10
Size C-4
Bus
description D-3
management lines D-5

C
CAL
VOFFSET 3-3, 15-7
CALCulate command summary 14-2
Calibration 16-1, 16-3, 16-4, 16-5, 16-7, F-2
Displaying count 16-15
Displaying dates 16-15
Resetting code 16-15
SCPI commands F-2
Calibration commands F-2
Calibration considerations 16-3
Calibration cycle 16-3
Calibration errors 16-4

D
Data
and stop bits 9-17
Format C-3
Data lines D-5
Data Store (Buffer) C-6
DC current calibrator 15-8, 15-10
DCL (device clear) 9-8
DDC C-1

DDC language 9-2, C-2
Default 1-10
Default settings 1-8
detected line frequency 1-7
Device C-2
Digital 4-10, 8-8, 8-10, 8-11, 8-12
Calibration C-8
filter 4-10, C-6
filter control 4-11
digital board revision levels 11-3
Digits 4-4, C-4
DISP test 17-4
display board revision levels 11-3
DISPlay command summary 14-6
display on or off 13-2
DISPlay subsystem 13-2
DISPlay, FORMat, and SYSTem 13-1
Displaying Rel 5-3

E
Electrometer Calibration 15-4
Electrostatic interference G-7
Enable register 10-2, 10-5
Enable registers 10-4, 10-5
engineering 4-3
Entering calibration dates 16-13
Environmental conditions 15-2
EOI and Bus Hold-off C-5
Equipment 16-3
Error
and status messages 9-9, B-2
queue 10-19
Errors 16-4
Event detectors 7-5
Event enable registers 10-16
Event registers 10-16
Example reading limits calculation 15-5
Execute C-8
External trigger example 7-13
External triggering 7-12

F
Features 1-5
Filtering 3-25
Filters 4-8
firmware revision level 1-7, 11-3
Floating 2-12
Floating measurements 2-12
Flow control, RS-232 (signal handshaking)
9-17
Focused ion beam applications G-25
Focused Ion Beam signal connections G-26
FORMat command summary 14-7

FORMat subsystem 13-4
Front 1-8
Front and rear panel 1-5
Front panel GPIB operation 9-9
Front panel tests 17-3

G
General 2-9
General IEEE-488 bus commands 9-7
General photo diode leakage G-23
GET (group execute trigger) 9-8
GPIB
Protocol selection E-4
GPIB 488.1 Protocol E-3
GPIB interface 9-2, 9-3
GPIB status indicators 9-9
GTL (go to local) 9-8
Guard plate 2-10
Guarding to reduce leakage currents G-3

H
Handler 8-7
Handling 1-4
Handling tips 2-10
Handshake lines D-5

I
identification query 11-3
Idle and initiate 7-4
IEEE
command groups D-13
IEEE-488
bus command summary D-7
bus configuration D-4
Bus Overview D-1
connector 9-4
documentation requirements E-2
SCPI Conformance Information E-1
IEEE-488 handshake sequence D-6
IEEE-488.2 common commands and queries
11-2
IFC (interface clear) 9-8
Input
connector 2-2
trigger requirements 7-12
Input bias current G-3
Inspection 1-3
Instruction Manual 1-4
Interface
available 9-2
configuration 9-3
function codes D-14
selection 9-3

Multiple command messages 9-14
Multiple response messages 9-15
mX 5-5
mX+b, m/X+b (reciprocal), and Logarithmic
5-5

Interlock 2-13, 2-14
internal wiring 2-10

K
Keithley 237-BNC-TRX 15-4, 16-4
Keithley 4801 15-4
Keithley CAP-18 15-4, 16-4
Keithley Model 5156 15-4, 16-4
KEY test 17-4

N
NAND 8-14
Noise G-5
Noise and safety shields 2-8
Noise and source impedance G-5
noisy readings G-7
NPLC Menu 4-7

L
Languages 9-2
Leakage currents and guarding G-2
Limit test configuration 8-16
Limit Tests 8-1
Limits configuration menu 8-16
Line 8-9
Line frequency 1-6
Line fuse location 17-3
Line fuse ratings 17-2
Line power connection 1-5
LLO (local lockout) 9-8
Locking out calibration 16-14
LOG C-3
Logarithmic 5-6
Long-form and short-form versions 9-12
Low noise input cables 2-3

M
Main 1-12
Making connections G-10
management lines, bus D-5
Manual ranging 4-2
manually keying in REL 5-3
Maximum 2-3
Maximum input levels 2-3
MEAN 6-7
Measure action 7-7
Measurement 3-2
measurement 2-16
Measurement considerations 2-14, G-2
measurement errors, avoiding G-10
Measurement event status 10-13
Measurement overview 2-2
Measurement ranges 4-2
Measurements 3-1
Measuring High Resistance Using the 6487
G-20
Measuring high resistance with external bias
source G-19
Median filter 4-9
Menu 1-12, 16-5
Model 6487 interface function codes D-14

O
Offset voltage calibration 15-7, 16-7
Ohms 3-11
OPER 3-18
Operating 3-25, 6-10
operating at a higher speed 13-2
Operation 8-6
consideration 4-11
event status 10-12
Optional command words 1-14
Output queue 10-18
Output trigger specifications 7-13
Output triggers 7-7
Overview of this manual 1-2

P
Package 1-4
Parity, RS-232 9-17
peak-to-peak 6-7
Performance 3-3
Performance verification 15-1
Performing 8-17
Phone number 1-3
Photodiode characterization prior to dicing
G-23
PIN photo diode leakage G-24
PKPK 6-7
polling sequence C-12
Pomona 1269 15-4, 16-4
Power-up 1-5
Power-up sequence 1-7
Primary address 9-6
Procedure 16-7
Program Message Terminator (PMT) 9-15
Program messages 9-13
Programming enable registers 10-5

Q
Query commands 1-14, 9-12

Questionable event status 10-14
Queues 10-17

R
Range 3-25, C-6
and values 4-5
symbols for rel values 5-3
Units, Digits, Rate, and Filters 4-1
range change transients G-12
Rate 3-25, 4-6
RATE Key 4-6
Reading limits for 20mA to 20mA ranges 15-8,
15-11
Reading limits for 2nA to 2mA ranges 15-9
Reading Mode C-2
Reading registers 10-6
Rear panel 1-5
Recall 6-2
Recalling 6-10
reciprocal 5-5
Recommended test equipment 15-3
Register bit descriptions 10-10
Registers
Bit descriptions 10-10
Condition 10-15
Enable registers 10-4, 10-5
Event 10-16
Reading 10-6
reinstate the previous Rel 5-2
REL 5-2
Relative, mX+b, m/X+b (Reciprocal), and Log
5-1
Remote 9-1
Remote calibration F-1
Remote setup operation 1-9
REN (remote enable) 9-7
resistivity 2-11
Response 9-15
Message Terminator (RMT) 9-16
time 4-11
restore setup 1-9
Routine maintenance 17-1
RS-232
connections 9-18
RS-232 interface 9-2, 9-3, 9-16
RS-232 settings 9-16

S
safety shield 3-9, 3-12, 3-17
Safety symbols and terms 1-3
Saving calibration 16-13
scientific (SCI) 4-3
SCPI 3-14, 3-19, 3-28, 8-15

SCPI commands D-11
amps function 3-10, 3-14
autozero 3-4
buffer 6-5, 6-13
reset registers and clear queues 10-4
system 13-9
triggering 7-10
SCPI errors, eliminating B-7
SCPI language 9-2
SCPI programming
filters 4-12
line frequency 1-6
mX+b, m/X+b, and log 5-7
range and digits 4-4
rate 4-7
relative 5-4
zero check and zero correct 3-6
SCPI Reference Tables 14-1
SCPI Signal Oriented Measurement Commands
12-1
SDC (selective device clear) 9-8
SDEViation 6-7
select power-on setup 1-9
Sending a response message 9-15
Sending and receiving data, RS-232 9-16
SENSe 14-7
SENSe command summary 14-10
serial number 1-12, 11-3
Serial polling and SRQ 10-9
Service request enable register 10-8
Setting 8-14
Setting and controlling relative 5-2
Setting line voltage and replacing line fuse 17-2
Shielding 2-8
shielding G-7, G-8
Shielding vs. Guarding G-10
Short-form rules 9-12
Single command messages 9-13
Sink 8-12
Source 6-11, 8-14
Source capacitance G-6
source impedance G-5
Source resistance G-5
Source Resistance (minimum recommended)
G-6
Sourcing 3-16
SPE, SPD (serial polling) 9-9, 10-9
SPE, SPD polling sequence C-12
Specifications A-1
Speed vs. noise characteristics 4-6
SRQ 10-7, C-5, E-8
Standard event status 10-10
Start 8-7
statistics 6-4

Status 1-8, C-11
Status and Error Messages B-1
Status byte
and mask interpretation C-14
and service request (SRQ) 10-7
format C-12
Status byte format C-14
Status byte register 10-7
STATus command summary 14-13
Status register sets 10-10
Status Structure 10-1
Status Word C-8
STD DEV 6-4
Store 6-2
Store Calibration C-5
Storing A-V ohms readings 3-23
Support 16-14
Sweep 6-10, 6-11
Sweeps 6-1
sweeps 6-8
Sweeps or A-V ohms in DDC mode C-10
SYSTem command summary 14-15

T
terminals 2-10
Terminator 9-17
Test 2-9
Test fixture 2-8
Test limit display messages 8-3
tests
front panel 17-3
timestamps 6-3
TRACe command summary 14-17
Triax 2-2
Trigger 7-5
TRIGger command summary 14-18
Trigger delay 7-6
Trigger Mode C-7
Trigger model
configuration 7-8
menu structure 7-8
Triggering 7-1
Typical addressed command sequence D-12
Typical bus sequence D-12
Typical command sequences D-12

U
U0 Status word C-11
U1 Status word C-12
U2 Status word C-12
Unaddress commands D-10
undetected errors G-7
Uniline commands D-9

Units 4-3
Universal multiline commands D-9
Unpacking 1-3
user setup 1-9
Using common commands and SCPI commands
in the same message 9-14

V
Verification limits 15-5
Verification test procedures 15-6
Verification test requirements 15-2
VOFFSET 16-6
Voltage 2-2, 2-4, 3-2, 3-3, 3-15, 3-18, F-5
Voltage burden G-4
Voltage source edit keys 3-15
voltage transients G-13

W
Warm-up period 3-3
Warranty information 1-3

Z
Zero 3-4, 3-5
Zero Check C-3

7.5X9BackCovr 12-06.qxd

1/10/07

2:45 PM

Page 1

Specifications are subject to change without notice.
All Keithley trademarks and trade names are the property of Keithley Instruments, Inc.
All other trademarks and trade names are the property of their respective companies.

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M E A S U R E

O F

C O N F I D E N C E

Keithley Instruments, Inc.
Corporate Headquarters • 28775 Aurora Road • Cleveland, Ohio 44139 • 440-248-0400 • Fax: 440-248-6168 • 1-888-KEITHLEY • www.keithley.com

12/06

Source Exif Data: File Type : PDF File Type Extension : pdf MIME Type : application/pdf PDF Version : 1.6 Linearized : No Author : Mark A. Chapman Create Date : 2011:08:15 09:57:21Z Keywords : 6487, voltage source, triggering, SCPI, Picoammeter, 6485 Modify Date : 2011:08:15 14:09:28-04:00 Has XFA : No XMP Toolkit : Adobe XMP Core 4.2.1-c043 52.372728, 2009/01/18-15:08:04 Producer : Acrobat Distiller 8.3.0 (Windows) Creator Tool : FrameMaker 7.2 Metadata Date : 2011:08:15 14:09:28-04:00 Format : application/pdf Title : Model 6487 Picoammeter/Voltage Source Creator : Mark A. Chapman Description : Model 6487 Picoammeter/Voltage Source Subject : 6487, voltage source, triggering, SCPI, Picoammeter, 6485 Document ID : uuid:bddbbd2f-3d55-4ebc-bba4-75007b11734d Instance ID : uuid:3e1389d0-c9f7-473e-9cf9-d1de14f89dd5 Page Mode : UseOutlines Page Count : 338 Warning : [Minor] Ignored duplicate Info dictionary EXIF Metadata provided byEXIF.tools

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