Lakeshore Learning Materials 642 Users Manual 642_v1.3

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Revision 1.3 P/N 119-042 9 January 2008

Lake Shore Cryotronics, Inc.

575 McCorkle Blvd.

Westerville, Ohio 43082-8888 USA

E-mail Addresses:

sales@lakeshore.com

service@lakeshore.com

Visit Our Website At:

www.lakeshore.com

Fax: (614) 891-1392

Telephone: (614) 891-2243

Methods and apparatus disclosed and described herein have been developed solely on company funds of Lake Shore Cryotronics, Inc. No government

or other contractual support or relationship whatsoever has existed which in any way affects or mitigates proprietary rights of Lake Shore Cryotronics,

Inc. in these developments. Methods and apparatus disclosed herein may be subject to U.S. Patents existing or applied for. Lake Shore Cryotronics,

Inc. reserves the right to add, improve, modify, or withdraw functions, design modifications, or products at any time without notice. Lake Shore shall

not be liable for errors contained herein or for incidental or consequential damages in connection with furnishing, performance, or use of this material.

User’s Manual

Model 642

Electromagnet

Power Su

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

LIMITED WARRANTY STATEMENT

WARRANTY PERIOD: ONE (1) YEAR

1. Lake Shore warrants that this Lake Shore product (the “Product”) will

be free from defects in materials and workmanship for the Warranty

Period specified above (the “Warranty Period”). If Lake Shore receives

notice of any such defects during the Warranty Period and the Product

is shipped freight prepaid, Lake Shore will, at its option, either repair

or replace the Product if it is so defective without charge to the owner

for parts, service labor or associated customary return shipping cost.

Any such replacement for the Product may be either new or equivalent

in performance to new. Replacement or repaired parts will be

warranted for only the unexpired portion of the original warranty or 90

days (whichever is greater).

2. Lake Shore warrants the Product only if it has been sold by an

authorized Lake Shore employee, sales representative, dealer or

original equipment manufacturer (OEM).

3. The Product may contain remanufactured parts equivalent to new in

performance or may have been subject to incidental use.

4. The Warranty Period begins on the date of delivery of the Product or

later on the date of installation of the Product if the Product is installed

by Lake Shore, provided that if you schedule or delay the Lake Shore

installation for more than 30 days after delivery the Warranty Period

begins on the 31st day after delivery.

5. This limited warranty does not apply to defects in the Product resulting

from (a) improper or inadequate maintenance, repair or calibration, (b)

fuses, software and non-rechargeable batteries, (c) software,

interfacing, parts or other supplies not furnished by Lake Shore, (d)

unauthorized modification or misuse, (e) operation outside of the

published specifications or (f) improper site preparation or

maintenance.

6. TO THE EXTENT ALLOWED BY APPLICABLE LAW, THE

ABOVE WARRANTIES ARE EXCLUSIVE AND NO OTHER

WARRANTY OR CONDITION, WHETHER WRITTEN OR ORAL,

IS EXPRESSED OR IMPLIED. LAKE SHORE SPECIFICALLY

DISCLAIMS ANY IMPLIED WARRANTIES OR CONDITIONS OF

MERCHANTABILITY, SATISFACTORY QUALITY AND/OR

FITNESS FOR A PARTICULAR PURPOSE WITH RESPECT TO

THE PRODUCT. Some countries, states or provinces do not allow

limitations on an implied warranty, so the above limitation or

exclusion might not apply to you. This warranty gives you specific

legal rights and you might also have other rights that vary from

country to country, state to state or province to province.

7. TO THE EXTENT ALLOWED BY APPLICABLE LAW, THE

REMEDIES IN THIS WARRANTY STATEMENT ARE YOUR

SOLE AND EXCLUSIVE REMEDIES.

8. EXCEPT TO THE EXTENT PROHIBITED BY APPLICABLE

LAW, IN NO EVENT WILL LAKE SHORE OR ANY OF ITS

SUBSIDIARIES, AFFILIATES OR SUPPLIERS BE LIABLE FOR

DIRECT, SPECIAL, INCIDENTAL, CONSEQUENTIAL OR

OTHER DAMAGES (INCLUDING LOST PROFIT, LOST DATA

OR DOWNTIME COSTS) ARISING OUT OF THE USE,

INABILITY TO USE OR RESULT OF USE OF THE PRODUCT,

WHETHER BASED IN WARRANTY, CONTRACT, TORT OR

OTHER LEGAL THEORY, AND WHETHER OR NOT LAKE

SHORE HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH

DAMAGES. Your use of the Product is entirely at your own risk.

Some countries, states and provinces do not allow the exclusion of

liability for incidental or consequential damages, so the above

limitation may not apply to you.

LIMITED WARRANTY STATEMENT (Continued)

9. EXCEPT TO THE EXTENT ALLOWED BY APPLICABLE LAW,

THE TERMS OF THIS LIMITED WARRANTY STATEMENT DO

NOT EXCLUDE, RESTRICT OR MODIFY, AND ARE IN

ADDITION TO, THE MANDATORY STATUTORY RIGHTS

APPLICABLE TO THE SALE OF THE PRODUCT TO YOU.

CERTIFICATION

Lake Shore certifies that this product has been inspected and tested in

accordance with its published specifications and that this product met its

published specifications at the time of shipment. The accuracy and

calibration of this product at the time of shipment are traceable to the

United States National Institute of Standards and Technology (NIST);

formerly known as the National Bureau of Standards (NBS).

FIRMWARE LIMITATIONS

Lake Shore has worked to ensure that the Model 642 firmware is as free

of errors as possible, and that the results you obtain from the instrument

are accurate and reliable. However, as with any computer-based software,

the possibility of errors exists.

In any important research, as when using any laboratory equipment,

results should be carefully examined and rechecked before final

conclusions are drawn. Neither Lake Shore nor anyone else involved in

the creation or production of this firmware can pay for loss of time,

inconvenience, loss of use of the product, or property damage caused by

this product or its failure to work, or any other incidental or consequential

damages. Use of our product implies that you understand the Lake Shore

license agreement and statement of limited warranty.

FIRMWARE LICENSE AGREEMENT

The firmware in this instrument is protected by United States copyright

law and international treaty provisions. To maintain the warranty, the

code contained in the firmware must not be modified. Any changes made

to the code is at the user’s risk. Lake Shore will assume no responsibility

for damage or errors incurred as result of any changes made to the

firmware.

Under the terms of this agreement you may only use the Model 642

firmware as physically installed in the instrument. Archival copies are

strictly forbidden. You may not decompile, disassemble, or reverse

engineer the firmware. If you suspect there are problems with the

firmware, return the instrument to Lake Shore for repair under the terms

of the Limited Warranty specified above. Any unauthorized duplication

or use of the Model 642 firmware in whole or in part, in print, or in any

other storage and retrieval system is forbidden.

TRADEMARK ACKNOWLEDGMENT

Many manufacturers and sellers claim designations used to distinguish

their products as trademarks. Where those designations appear in this

manual and Lake Shore was aware of a trademark claim, they appear with

initial capital letters and the ™ or ® symbol.

CalCurve™, Cernox™, Duo-Twist™, Quad-Lead™, Quad-Twist™,

Rox™, and SoftCal™ are trademarks of Lake Shore Cryotronics, Inc.

MS-DOS® and Windows® are trademarks of Microsoft Corp.

NI-488.2™ is a trademark of National Instruments.

PC, XT, AT, and PS-2 are trademarks of IBM.

stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying,

recording, or otherwise, without the express written permission of Lake Shore.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

iii

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

This Page Intentionally Left Blank

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Table of Contents v

TABLE OF CONTENTS

Chapter/Section Title Page

1 INTRODUCTION .................................................................................................................................................... 1-1

1.0 GENERAL............................................................................................................................................. 1-1

1.1 DESCRIPTION...................................................................................................................................... 1-1

1.2 SPECIFICATIONS ................................................................................................................................ 1-3

1.3 SAFETY SUMMARY............................................................................................................................. 1-7

1.4 SAFETY SYMBOLS.............................................................................................................................. 1-9

2 MAGNET SYSTEM DESIGN, INSTALLATION, AND OPERATION...................................................................... 2-1

2.0 GENERAL............................................................................................................................................. 2-1

2.1 INTRODUCTION................................................................................................................................... 2-1

2.2 MAGNET CONSTRUCTION................................................................................................................. 2-2

2.3 CONNECTING THE MAGNET.............................................................................................................. 2-2

2.3.1 Water Hose Connection .................................................................................................................... 2-2

2.3.2 Magnet Coil Wiring ............................................................................................................................ 2-2

2.3.3 Temperature Switches and Flow Switches........................................................................................ 2-4

2.3.4 Cooling Water and Water Valve ........................................................................................................ 2-4

2.3.5 Grounding.......................................................................................................................................... 2-4

2.3.6 Final Check-Out................................................................................................................................. 2-5

2.4 ELECTROMAGNET OPERATION........................................................................................................ 2-5

2.4.1 Air Gap and Pole Caps...................................................................................................................... 2-5

2.4.2 Maximum Power and Current............................................................................................................ 2-5

2.4.3 Operation Under Field Control........................................................................................................... 2-7

2.4.4 Avoiding Cooling Water Condensation.............................................................................................. 2-8

3 INSTALLATION...................................................................................................................................................... 3-1

3.0 GENERAL............................................................................................................................................. 3-1

3.1 INSPECTION AND UNPACKING ......................................................................................................... 3-1

3.1.1 Moving and Handling ............................................................................................................................ 3-1

3.2 REAR PANEL DEFINITION.................................................................................................................. 3-2

3.3 POWER WIRING AND SET-UP............................................................................................................ 3-3

3.3.1 Line Voltage Selection....................................................................................................................... 3-3

3.3.2 Circuit Breaker Setting....................................................................................................................... 3-4

3.3.3 Start-Up Fuses .................................................................................................................................. 3-5

3.3.4 Cable Entry........................................................................................................................................ 3-5

3.3.5 Power Input Terminals....................................................................................................................... 3-5

3.3.6 Wiring Cover...................................................................................................................................... 3-6

3.3.7 Mains Wiring...................................................................................................................................... 3-7

3.4 MAGNET CONNECTOR....................................................................................................................... 3-7

3.5 AUXILIARY CONNECTOR ................................................................................................................... 3-7

3.6 POWER SUPPLY CONNECTOR ......................................................................................................... 3-8

3.7 COOLING WATER................................................................................................................................ 3-8

3.8 MAGNET CABLE CONNECTIONS....................................................................................................... 3-9

3.9 ANALOG INPUT/OUTPUT CONNECTIONS ...................................................................................... 3-11

3.9.1 External Current Programming........................................................................................................ 3-11

3.9.2 Output Current and Voltage Monitors .............................................................................................. 3-11

3.10 COMPUTER INTERFACE .................................................................................................................. 3-11

3.10.1 RS-232C Interface Connection........................................................................................................ 3-11

3.10.2 IEEE-488 Interface Connection ....................................................................................................... 3-11

3.11 CHASSIS CONNECTION ................................................................................................................... 3-11

3.12 DETACHABLE HANDLES .................................................................................................................. 3-12

3.13 RACK MOUNTING.............................................................................................................................. 3-12

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

vi Table of Contents

TABLE OF CONTENTS (Continued)

Chapter/Section Title Page

4 OPERATION...........................................................................................................................................................4-1

4.0 GENERAL.............................................................................................................................................4-1

4.1 TURNING POWER ON......................................................................................................................... 4-1

4.2 DISPLAY DEFINITION..........................................................................................................................4-2

4.3 LED ANNUNCIATORS.......................................................................................................................... 4-2

4.3.1 Fault LED...........................................................................................................................................4-2

4.3.2 Compliance LED................................................................................................................................4-2

4.3.3 Power Limit LED................................................................................................................................ 4-2

4.3.4 Ramping LED ....................................................................................................................................4-2

4.3.5 Remote LED......................................................................................................................................4-2

4.4 KEYPAD DEFINITION .......................................................................................................................... 4-3

4.4.1 General Keypad Operation................................................................................................................ 4-4

4.5 DISPLAY SETUP ..................................................................................................................................4-4

4.6 SETTING OUTPUT CURRENT ............................................................................................................4-4

4.7 CURRENT RAMP RATE.......................................................................................................................4-5

4.8 RAMP SEGMENTS............................................................................................................................... 4-5

4.9 PAUSE RAMP.......................................................................................................................................4-6

4.10 ZERO OUTPUT ....................................................................................................................................4-6

4.11 MAXIMUM SETTING LIMITS................................................................................................................4-7

4.11.1 Maximum Output Current ..................................................................................................................4-7

4.11.2 Maximum Current Ramp Rate ...........................................................................................................4-7

4.12 MAGNET WATER.................................................................................................................................4-8

4.13 INTERNAL WATER...............................................................................................................................4-8

4.14 ERROR STATUS DISPLAY..................................................................................................................4-8

4.15 EXTERNAL CURRENT PROGRAMMING ............................................................................................ 4-9

4.16 LOCKING THE KEYPAD ......................................................................................................................4-9

4.17 COMPUTER INTERFACE .................................................................................................................. 4-10

4.17.1 Changing Serial Baud Rate ............................................................................................................. 4-10

4.17.2 Changing IEEE-488 Interface parameters ....................................................................................... 4-11

4.18 DEFAULT PARAMETER VALUES...................................................................................................... 4-11

5 COMPUTER INTERFACE OPERATION................................................................................................................5-1

5.0 GENERAL.............................................................................................................................................5-1

5.1 IEEE-488 INTERFACE..........................................................................................................................5-1

5.1.1 Changing IEEE-488 Interface Parameters......................................................................................... 5-2

5.1.2 Remote/Local Operation.................................................................................................................... 5-2

5.1.3 IEEE-488 Command Structure .......................................................................................................... 5-2

5.1.3.1 Bus Control Commands .................................................................................................................5-3

5.1.3.2 Common Commands .....................................................................................................................5-3

5.1.3.3 Device Specific Commands ........................................................................................................... 5-3

5.1.3.4 Message Strings ............................................................................................................................5-3

5.1.4 Status System ...................................................................................................................................5-4

5.1.4.1 Overview........................................................................................................................................ 5-4

5.1.4.1.1 Condition Registers .................................................................................................................... 5-4

5.1.4.1.2 Event Registers ..........................................................................................................................5-4

5.1.4.1.3 Enable Registers ........................................................................................................................5-4

5.1.4.1.4 Status Byte Register...................................................................................................................5-4

5.1.4.1.5 Service Request Enable Register...............................................................................................5-4

5.1.4.1.6 Reading Registers...................................................................................................................... 5-7

5.1.4.1.7 Programming Registers..............................................................................................................5-7

5.1.4.1.8 Clearing Registers...................................................................................................................... 5-7

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Table of Contents vii

TABLE OF CONTENTS (Continued)

Chapter/Section Title Page

5.1.4.2 Status Register Sets ...................................................................................................................... 5-8

5.1.4.2.1 Standard Event Status Register ................................................................................................. 5-8

5.1.4.2.2 Operation Event Register Set..................................................................................................... 5-9

5.1.4.3 Error Status Register Sets ........................................................................................................... 5-10

5.1.4.3.1 Hardware Error Status Register Set ......................................................................................... 5-10

5.1.4.3.2 Operational Error Status Register Set ...................................................................................... 5-11

5.1.4.4 Status Byte and Service Request (SRQ) ..................................................................................... 5-12

5.1.4.4.1 Status Byte Register................................................................................................................. 5-12

5.1.4.4.2 Service Request Enable Register............................................................................................. 5-13

5.1.4.4.3 Using Service Request (SRQ) and Serial Poll.......................................................................... 5-13

5.1.4.4.4 Using Status Byte Query (*STB) .............................................................................................. 5-13

5.1.4.4.5 Using Message Available (MAV) Bit)........................................................................................ 5-13

5.1.4.4.6 Using Operation Complete (*OPC) and Operation Complete Query (*OPC?).......................... 5-14

5.1.5 IEEE-488 Interface Example Programs........................................................................................... 5-14

5.1.5.1 IEEE-488 Interface Board Installation for Visual Basic Program.................................................. 5-14

5.1.5.2 Visual Basic IEEE-488 Interface Program Setup ......................................................................... 5-16

5.1.5.3 Program Operation ...................................................................................................................... 5-20

5.1.6 Troubleshooting............................................................................................................................... 5-20

5.2 SERIAL INTERFACE OVERVIEW...................................................................................................... 5-21

5.2.1 Changing Baud Rate ....................................................................................................................... 5-21

5.2.2 Physical Connection........................................................................................................................ 5-21

5.2.3 Hardware Support ........................................................................................................................... 5-22

5.2.4 Character Format ............................................................................................................................ 5-22

5.2.5 Message Strings.............................................................................................................................. 5-22

5.2.6 Message Flow Control..................................................................................................................... 5-23

5.2.7 Serial Interface Example Programs................................................................................................. 5-23

5.2.7.1 Visual Basic Serial Interface Program Setup ............................................................................... 5-24

5.2.7.2 Program Operation ...................................................................................................................... 5-27

5.2.8 Troubleshooting............................................................................................................................... 5-27

5.3 COMMAND SUMMARY...................................................................................................................... 5-28

5.3.1 Interface Commands (Alphabetical Listing) ..................................................................................... 5-29

6 OPTIONS AND ACCESSORIES............................................................................................................................ 6-1

6.0 GENERAL............................................................................................................................................. 6-1

6.1 ACCESSORIES INCLUDED................................................................................................................. 6-1

6.2 ACCESSORIES AVAILABLE................................................................................................................ 6-1

7 SERVICE ................................................................................................................................................................ 7-1

7.0 GENERAL............................................................................................................................................. 7-1

7.1 CONTACTING LAKE SHORE CRYOTRONICS ................................................................................... 7-1

7.2 RETURNING PRODUCTS TO LAKE SHORE...................................................................................... 7-1

7.3 LINE VOLTAGE SELECTION............................................................................................................... 7-2

7.4 CIRCUIT BREAKER SETTING............................................................................................................. 7-3

7.5 POWER LINE FUSE REPLACEMENT .................................................................................................7-4

7.6 ERROR MESSAGES............................................................................................................................ 7-5

7.7 ELECTROSTATIC DISCHARGE .......................................................................................................... 7-6

7.7.1 Identification of Electrostatic Discharge Sensitive Components ........................................................ 7-6

7.7.2 Handling Electrostatic Discharge Sensitive Components .................................................................. 7-7

7.8 ENCLOSURE BOTTOM REMOVAL AND REPLACEMENT................................................................. 7-7

7.8.1 Removal ............................................................................................................................................ 7-7

7.8.2 Installation ......................................................................................................................................... 7-7

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

viii Table of Contents

TABLE OF CONTENTS (Continued)

Chapter/Section Title Page

7.9 FIRMWARE REPLACEMENT............................................................................................................... 7-7

7.10 CONNECTOR AND CABLE DEFINITIONS ........................................................................................ 7-11

7.10.1 Analog I/O Connector ......................................................................................................................7-11

7.10.2 Magnet Connector ........................................................................................................................... 7-11

7.10.3 Auxiliary Connector..........................................................................................................................7-12

7.10.4 Power Supply Connector................................................................................................................. 7-13

7.10.5 RS-232C Serial Interface Connector ...............................................................................................7-13

7.10.6 Serial Interface Cable Wiring ...........................................................................................................7-14

7.10.7 IEEE-488 Parallel Interface Connector............................................................................................7-14

7.11 CALIBRATION .................................................................................................................................... 7-16

7.11.1 Calibration Interface.........................................................................................................................7-16

7.11.2 Calibration Equipment .....................................................................................................................7-17

7.11.3 Calibration Procedure...................................................................................................................... 7-17

7.11.3.1 Calibrate Current Output Zero...................................................................................................... 7-17

7.11.3.2 Calibrate Current Reading Zero ................................................................................................... 7-17

7.11.3.3 Calibrate Output Voltage Reading Zero ....................................................................................... 7-18

7.11.3.4 Calibrate External Program Voltage Reading Zero ...................................................................... 7-18

7.11.3.5 Calibrate Output Current Gain (Span).......................................................................................... 7-18

7.11.3.6 Calibrate Current Reading Gain...................................................................................................7-20

7.11.3.7 Calibrate Voltage Reading Gain...................................................................................................7-20

7.11.3.8 Calibrate External Current Programming Voltage Reading Gain ................................................. 7-21

7.11.4 Calibrate Specific Interface Commands........................................................................................... 7-21

APPENDIX A – GLOSSARY OF TERMINOLOGY....................................................................................................... A-1

APPENDIX B – UNITS FOR MAGNETIC PROPERTIES............................................................................................. B-1

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Table of Contents ix

LIST OF ILLUSTRATIONS

Figure No. Title Page

1-1 Model 642 Front Panel ............................................................................................................................. 1-2

2-1 A Typical Electromagnet........................................................................................................................... 2-1

2-2 Typical Magnet Water Hook-Up................................................................................................................ 2-2

2-3 Typical Magnet Coil Wiring Showing Series and Parallel Connections..................................................... 2-3

2-4 Typical Thermal Switch, Flow Switch and Valve Wiring............................................................................ 2-4

2-5 Typical Curves of Field vs. Current for Various Air Gaps and Pole Cap Sizes ......................................... 2-5

3-1 Model 642 Rear Panel.............................................................................................................................. 3-3

3-2 Voltage Change Detail.............................................................................................................................. 3-4

3-3 Circuit Breaker.......................................................................................................................................... 3-4

3-4 Fuses........................................................................................................................................................ 3-5

3-5 Typical Cable Entry with Bushing ............................................................................................................. 3-5

3-6 Typical Power Input Wiring....................................................................................................................... 3-6

3-7 Wiring Cover Installation........................................................................................................................... 3-6

3-8 Typical Magnet Connector Wiring............................................................................................................. 3-7

3-9 Typical Auxiliary Connector Wiring ........................................................................................................... 3-7

3-10 Typical Power Supply Connector Wiring................................................................................................... 3-8

3-11 Typical Water Hose Connection ............................................................................................................... 3-8

3-12 Water Valve Connection........................................................................................................................... 3-9

3-13 Output Cable Connection ....................................................................................................................... 3-10

3-14 Output Lug Cover Installation ................................................................................................................. 3-10

3-15 Analog Input/Output Connector .............................................................................................................. 3-11

3-16 Mounting Hole Pattern............................................................................................................................ 3-12

4-1 Model 642 Power Push Buttons ............................................................................................................... 4-1

4-2 Model 642 Keypad and LED Layout ......................................................................................................... 4-3

5-1 Model 642 Status System......................................................................................................................... 5-5

5-2 Standard Event Status Register................................................................................................................ 5-8

5-3 Operation Event Register ......................................................................................................................... 5-9

5-4 Hardware Error Status Register.............................................................................................................. 5-10

5-5 Operational Error Status Register........................................................................................................... 5-11

5-6 Status Byte Register and Service Request Enable Register .................................................................. 5-12

5-7 GPIB0 Setting Configuration................................................................................................................... 5-15

5-8 DEV 12 Device Template Configuration ................................................................................................. 5-15

5-9 Typical National Instruments GPIB Configuration from IBCONF.EXE.................................................... 5-19

7-1 Model 642 Rear Panel.............................................................................................................................. 7-2

7-2 Voltage Change Detail.............................................................................................................................. 7-3

7-3 Circuit Breaker.......................................................................................................................................... 7-4

7-4 Fuse Holder Detail.................................................................................................................................... 7-5

7-5 Board Locations........................................................................................................................................ 7-9

7-6 Digital Board Parts Locations ................................................................................................................. 7-10

7-7 Analog I/O Connector Details ................................................................................................................. 7-11

7-8 Magnet Connector Details ...................................................................................................................... 7-11

7-9 Auxiliary Connector Detail ...................................................................................................................... 7-12

7-10 Power Supply Connector Details ............................................................................................................ 7-13

7-11 RS-232C (DTE) Connector Details......................................................................................................... 7-13

7-12 IEEE-488 Connector Details................................................................................................................... 7-15

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

x Table of Contents

LIST OF TABLES

Table No. Title Page

3-1 Rear Panel Connector Identification .........................................................................................................3-2

3-2 Voltage and Current Selection.................................................................................................................. 3-3

3-3 Current Capacity and Total Lead Lengths ................................................................................................ 3-9

4-1 Model 642 LED Descriptions .................................................................................................................... 4-2

4-2 Model 642 Key Descriptions ..................................................................................................................... 4-3

4-3 Default Parameter Values....................................................................................................................... 4-12

5-1 Binary Weighting of an 8-Bit Register .......................................................................................................5-7

5-2 Register Clear Methods ............................................................................................................................5-7

5-3 Programming Example to Generate an SRQ.......................................................................................... 5-13

5-4 IEEE-488 Interface Program Control Properties ..................................................................................... 5-17

5-5 Visual Basic IEEE-488 Interface Program ..............................................................................................5-18

5-6 Serial Interface Specifications................................................................................................................. 5-22

5-7 Serial Interface Program Control Properties ........................................................................................... 5-25

5-8 Visual Basic Serial Interface Program.....................................................................................................5-26

5-9 Command Summary............................................................................................................................... 5-29

7-1 Voltage and Current Selection.................................................................................................................. 7-3

7-2 Instrument Hardware Errors......................................................................................................................7-5

7-3 Operational Errors ....................................................................................................................................7-6

B-1 Conversion from CGS to SI Units .............................................................................................................B-1

B-2 Recommended SI Values for Physical Constants.....................................................................................B-2

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Introduction 1-1

CHAPTER 1

INTRODUCTION

1.0 GENERAL

This chapter provides an introduction to the Model 642 Electromagnet Power Supply. The Model 642 was designed and

manufactured in the United States of America by Lake Shore Cryotronics, Inc. The Model 642 features include the

following.

• True 4-quadrant (bipolar) 70 A, 35 V output

• 0.1 mA output setting resolution

• Linear regulation minimizes noise and ripple to 0.007% of maximum current into a 0.50 Ω load

• 1.0 mA stability per hour, 5 mA per 24 hour

• CE compliance to both the low voltage directive and the electromagnetic compatibility (EMC) directive

1.1 DESCRIPTION

The Model 642 Electromagnet Power Supply is the ideal supply for small- to medium-sized magnets used in

high-sensitivity materials research applications. The Model 642 is a practical alternative to both the larger one-size-fits-

all magnet supplies and the endless adaptations of generic power supplies. By optimizing output power, Lake Shore was

able to concentrate on the performance requirements of the most demanding magnet users. The resulting Model 642

provides high precision, low noise, safety, and convenience.

Precision in magnetic measurements is typically defined as smooth continuous operation with high setting resolution and

low drift. Achieving these goals while driving an inductive load requires unique solutions. The Model 642 delivers up to

70 A at a nominal voltage of 35 V, with the supply acting as either a source or a sink in true 4-quadrant operation. Its

current source output architecture with analog control enables both smooth operation and low drift. A careful blending of

analog and digital circuits provides high setting resolution of 0.1 mA and flexible output programming.

Lake Shore chose linear input and output power stages for the nominal 2450 W output of the Model 642. Linear

operation eliminates the radiated radio frequency (RF) noise associated with switching power supplies, allowing the

Model 642 to reduce the overall noise in its output and the noise radiated into surrounding electronics.

Safety should never be an afterthought when driving an inductive load. The Model 642 incorporates a variety of

hardware and firmware protection features to ensure the safety of the magnet and supply. For improved operator safety,

the power supply was also designed for compliance with the safety requirements of the CE mark, including both the low

voltage and the electromagnetic compatibility (EMC) directive.

Instrument users have come to rely on Lake Shore equipment for convenience and ease of use. The Model 642 includes

features such as built-in current and power limits, internal cooling-water and magnet-water control to minimize

condensation, current ramping and the capability to modulate the output current. Computer interfaces are also integrated

for automation of the magnet system. The Model 642 is truly an excellent one-box solution for controlling an

electromagnet.

Output Architecture

True 4-quadrant output capability of the Model 642 is ideal for the charge and discharge cycling of electromagnets for

both positive and negative fields. Tightly integrated analog control of the 4-quadrant output provides smooth current

change with very low overshoot on output change. The Model 642 has the ability to charge and discharge magnets up

to a 50 A per second rate into a nominal 0.5 Ω, 0.5 H load.

True 4-quadrant operation eliminates the need for external switching or operator intervention to reverse the current

polarity, significantly simplifying system operation. The transition through zero current is smooth and continuous,

allowing the user to readily control the magnetic field as polarity changes.

At static fields, output current drift is also kept low by careful attention in the analog control circuits and layout.

The high stability and low noise of the Model 642 provides a quiet and uniform magnetic field.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

1-2 Introduction

Output Architecture (Continued)

The Model 642 output architecture relies on low noise, linear input and output stages. The linear circuitry of the Model

642 permits operation with less electrical noise than switch-mode electromagnet power supplies. One key benefit of this

architecture is CE compliance to the electromagnetic compatibility (EMC) directive, including the radiated emissions

requirement.

Output Programming

The Model 642 output current is programmed internally via the keypad, externally by the computer interface, externally

by the analog programming input, or by the sum of the external and internal settings. For internal programming, the

Model 642 incorporates a proprietary digital-to-analog converter (DAC) that is monotonic over the entire output range

and provides a resolution of 0.1 mA.

The Model 642 generates extremely smooth and continuous ramps with virtually no overshoot. The digitally generated

constant current ramp rate is variable between 0.1 mA/s and 99.999 A/s. To ensure a smooth ramp rate, the power supply

updates the high-resolution DAC 23.7 times per second. A low-pass filter on the DAC output smoothes the transitions at

step changes during ramping.

Output Readings

The Model 642 provides high-resolution output readings. The output current reading has a resolution of 0.1 mA. The

output voltage reading reports the voltage at the output terminals with a resolution of 0.1 mV. All output readings can be

prominently displayed on the front panel and read over the computer interface.

Protection

The Model 642 continuously monitors the line voltage, load power, internal power, and load resistance as well as a

variety of other internal circuit parameters for signs of trouble. Some fault conditions result in a warning message while

others will provide a warning message and zero the output. When hazardous conditions exist, the Model 642 will shut

itself off.

NOTE: The Model 642 is equipped with a high-line lockout circuit which will prevent the unit from being turned

on if it is connected to a voltage source that is much higher than the voltage for which it is configured.

Figure 1-1. Model 642 Front Panel

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Introduction 1-3

Description (Continued)

Interfaces

The Model 642 includes IEEE-488 and RS-232C interfaces that provide access to operating data, stored parameters, and

remote control of all front panel operated functions. A keypad lock-out feature is provided to prohibit any changes made

from the front panel. The Model 642 can then be operated solely with the computer via the RS-232C or IEEE-488

interface.

The Model 642 provides two analog outputs to monitor the output current and voltage. Each output is a buffered,

differential, analog voltage representation of the signal being monitored. The current monitor has a sensitivity of

7 V = 70 A, while the voltage monitor has a sensitivity of 3.5 V = 35 V.

Display and Keypad

The Model 642 incorporates a large 8-line by 40-character vacuum fluorescent display. Output current and output

voltage readings are displayed simultaneously. Five LEDs on the front panel provide quick verification of instrument

status, including ramping, power limit, compliance, fault, and computer interface mode. Error conditions are indicated on

the main display along with an audible tone. Extended error descriptions are available in an error message screen by

pressing the Status key.

The keypad is arranged logically to separate the different functions of the instrument. The most common functions of the

power supply are accessed using a single key press. The keypad can be locked to either lock out all changes or to lock

out just the instrument setup parameters allowing the output of the power supply to be changed.

1.2 SPECIFICATIONS

Output

Type Bipolar, 4-quadrant, DC current source

Current generation Fully linear regulation with digital setting and analog control

Current range ±70 A

Compliance voltage (DC) ±35 V nominal

Power 2450 W nominal

Nominal load 0.5 Ω, 0.5 H

Maximum load resistance 0.6 Ω for ±70 A DC operation at +10% to –5% line voltage

Minimum load resistance 0.4 Ω for ±70 A at +5% to –10% line voltage

Load inductance range 0 H to 1 H

Current ripple 5 mA RMS (0.007%) at 70 A into nominal load

Current ripple frequency Dominated by the line frequency and its harmonics

Temperature coefficient ±15 ppm of full scale/°C

Line regulation ±60 ppm of full scale/10% line change

Stability (1 h) 1 mA/h (after warm-up)

>Stability (24 h) 5 mA/24 h (typical, dominated by temperature coefficient and line regulation)

Isolation Differential output is optically isolated from chassis to prevent ground loops

Slew rate 50 A/s into nominal load

650 A/s maximum into a resistive load

Compliance voltage (AC) ±43 V at +10% to –5% line

Settling time <1 s for 10% step to within 1 mA of output into nominal load

Modulation response ≤ 0.17 Hz at ±70 A sine wave into nominal load, <0.02% THD

≤ 10 Hz at ±10 A sine wave into nominal load, <0.10% THD

Attenuation –0.5 dB at 10 Hz

Protection Short circuit, line loss, low line voltage, high line voltage, output over voltage, output

over current, and over temperature

Connector Two lugs with 6.4 mm (0.25 in) holes for M6 or 0.25 in bolts

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

1-4 Introduction

Specifications (Continued)

Output programming

Internal current setting

Resolution 0.1 mA (20 bit)

Settling time 600 ms for 1% step to within 1 mA (of internal setting)

Accuracy ±10 mA ±0.05% of setting

Operation Keypad, computer interface

Protection Programmable current setting limit

Internal current ramp

Ramp rate 0.1 mA/s to 99.999 A/s (compliance limited)

Update rate 23.7 increments/s

Ramp segments 5

Operation Keypad, computer interface

Protection Programmable ramp rate limit

External current programming

Sensitivity 10 V/70 A

Resolution Analog

Accuracy ±10 mA ±1% of setting

Input resistance 20 kΩ

Operation Voltage program through rear panel, can be summed with internal current setting

Limits Internally clamped at ±10.1 V and bandwidth limited at 40 Hz to protect output

Connector Shared 15-pin D-sub

Readings

Output current

Resolution 0.1 mA

Accuracy ±5 mA ±0.05% of rdg

Update rate 2.5 rdg/s display, 10 rdg/s interface

Output voltage (at supply terminals)

Resolution 1mV

Accuracy ±5 mV ±0.05% of rdg

Update rate 2.5 rdg/s display, 5 rdg/s interface

Front panel

Display type 8-line by 40-character graphic vacuum fluorescent display module

Display readings Output current, output voltage, and internal water temperature

Display settings Output current and ramp rate

Display annunciators Status and errors

LED annunciators Fault, Compliance, Power Limit, Ramping, Remote

Audible annunciator Errors and faults

Keypad type 26 full travel keys

Keypad functions Direct access to common operations, menu-driven setup

Power White flush ON and black extended OFF push buttons

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Introduction 1-5

Specifications (Continued)

Interface

IEEE-488.2 interface

Features SH1, AH1, T5, L4, SR1, RL1, PP0, DC1, DT0, C0, E1

Reading rate To 10 rdg/s

Software support National Instruments LabVIEW™ driver (consult Lake Shore for availability)

Serial interface

Electrical format RS-232C

Baud rates 9600, 19200, 38400, 57600

Reading rate To 10 rdg/s

Connector 9-pin D-sub (DTE)

Output current monitor

Sensitivity 7 V/70 A

Accuracy ±1% of full scale

Noise 1 mV RMS

Source impedance 20 Ω

Connector Shared 15-pin D-sub

Output voltage monitor

Sensitivity 3.5 V/35 V

Accuracy 1% of full scale

Noise 1 mV RMS

Source impedance 20 Ω

Connector Shared 15-pin D-sub

Power supply cooling water

Remote enable input TTL low or contact closure to enable output; jumper required if unused

Valve power output 24 VAC at 1 A maximum, automatic or manual control

Connector Shared 4-pin detachable terminal block

Flow switch and water valve optional

Magnet cooling water

Remote enable input TTL low or contact closure to enable output; jumper required if unused

Valve power output 24 VAC at 1 A maximum, automatic or manual control

Connector Shared 4-pin detachable terminal block

Flow switch, temperature switch, and water valve not included

Auxiliary

Emergency stop Requires 1 A, 24 VAC normally closed (NC) contact to enable power-up; jumper required if

unused

Fault output Relay with normally open (NO) or normally closed (NC) contact, 30 VDC at 1 A

Remote enable TTL low or contact closure to enable output, jumper required if unused

Connector Shared 8-pin detachable terminal block

Emergency stop and enable switches not included

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

1-6 Introduction

Specifications (Continued)

General

Line power

Power 5500 VA max

Voltage and current 200/208 VAC ±10%, 13 A/phase

220/230 VAC ±10%, 12 A/phase

380 VAC ±10%, 7 A/phase

400/415 VAC ±10%, 6.5 A/phase

Protection Three phase thermal relay, with adjustable current setting

Two class CC 1/4 A fuses

Over-voltage lockout circuit

Frequency 50 Hz or 60 Hz

Configuration 3-phase delta

Connector 4-pin terminal block

Line voltage must be specified at time of order but is field reconfigurable

Cable from power supply to facility power not included

Cooling water

Flow rate 5.7 L (1.5 gal)/min minimum

Pressure range 34 kPa (5 psi) to 552 kPa (80 psi)

Pressure drop 10 kPa (1.5 psi) at 5.7 L (1.5 gal)/minute minimum for power supply only

Temperature 15 °C to 30 °C (non condensing)

Connection Two 10 mm (0.38 in) hose barbs

CAUTION: Internal condensation can cause damage to the power supply

Enclosure type 7 U high, 19 in rack mount with integral rack mount ears (25 mm (1 in) air space required on

each side for ventilation

Size 483 mm W × 310 mm H × 572 mm D (19 in × 12.2 in × 22.5 in) with front handles removed

Weight 74 kg (163 lb)

Shipping size 635 mm W × 559 mm H × 736 mm D (25 in × 22 1n × 29 in)

Shipping weight 79.5 kg (175 lb)

Ambient temperature 15 °C to 35 °C at rated accuracy, 5 °C to 40 °C at reduced accuracy

Humidity Non condensing

Warm-up 30 min at output current setting

Approvals CE mark – low voltage compliance to EN61010-3, EMC compliance to EN55022-1

Calibration schedule 1 year

Ordering Information

Part Number Ordering Information

642-204 Model 642 ±70 A ±35 V, 2.5 kW, 204/208 VAC

642-225 Model 642 ±70 A ±35 V, 2.5 kW, 220/230 VAC

642-380 Model 642 ±70 A ±35 V, 2.5 kW, 380 VAC

642-408 Model 642 ±70 A ±35 V, 2.5 kW, 400/415 VAC

Options

6041 Water flow switch, 2 gallons/min

6042 64X MPS water valve with mounting bracket and hose barb fittings

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Introduction 1-7

Accessories included

MAN-642 Model 642 user manual

6031 Two front handles

6032 Two rear handles

6051 Terminal block, 4 pin

6052 Terminal block, 8 pin

6252 15-pin D-sub mating connector, analog I/O

108-654 Strain relief bushing kit

----- Calibration certificate

Accessories available

6201 1 m (3.3 ft) long IEEE-488 (GPIB) computer interface cable

6261 3 m (10 ft) magnet cable kit, AWG 4

6262 6 m (20 ft) magnet cable kit, AWG 4

CAL-642-CERT Instrument recalibration with certificate

CAL-642-DATA Instrument recalibration with certificate and data

1.3 SAFETY SUMMARY

Observe these safety precautions during all phases of instrument operation, service, and repair. Failure to comply with

these precautions or with specific warnings elsewhere in this manual violates safety standards of design, manufacture,

and intended instrument use. Lake Shore assumes no liability for Customer failure to comply with these requirements.

The Model 642 protects the operator and surrounding area from electric shock or burn, mechanical hazards, excessive

temperature, and spread of fire from the instrument. Environmental conditions outside of the conditions below may pose

a hazard to the operator and surrounding area.

• Indoor use.

• Altitude to 2000 meters.

• Temperature for safe operation: 5 °C to 40 °C.

• Over voltage category II.

• Pollution degree 2.

• Maximum relative humidity: 80% for temperature up to

31 °C decreasing linearly to 50% at 40 °C.

• Power supply voltage fluctuations not to exceed ±10%

of the nominal voltage.

Power and Ground Connections

This instrument must be connected to a dedicated three-phase power circuit with proper size of circuit breaker. (Refer

to Chapter 3 – Installation) Verify that the unit has been configured for the correct input voltage. The neutral line, if

available, is not used. The unit may be hard-wired or connected with a flexible cable and plug. In all cases the correct

size wire must be chosen for the current drawn and the length of cable used. To minimize shock hazard, the electrical

ground (safety ground) lead must be connected. If a flexible cable and plug are used, plug the power cable into an

approved electrical outlet. The power jack and mating plug of the power cable must meet Underwriters Laboratories

(UL) and International Electromechanical Commission (IEC) safety standards. Power wiring must comply with

electrical codes of the locality in which the unit is installed.

Ventilation

The instrument has ventilation holes in its side panels. Do not block these holes when the instrument is operating.

Provide at least 25 mm (1 in) of air space on each side for ventilation.

Do Not Operate In An Explosive Atmosphere

Do not operate the instrument in the presence of flammable gases or fumes. Operation of any electrical instrument

in such an environment constitutes a definite safety hazard.

Keep Away From Live Circuits

Operating personnel must not remove instrument covers. Refer component replacement and internal adjustments to

qualified maintenance personnel. Do not replace components with power cable connected. To avoid injuries, always

disconnect power and discharge circuits before touching them.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

1-8 Introduction

Safety Summary (Continued)

Do Not Substitute Parts Or Modify Instrument

Do not install substitute parts or perform any unauthorized modification to the instrument. Return the instrument to an

authorized Lake Shore representative for service to ensure that safety features are maintained.

Prevent Cooling Water Condensation

Do not operate the power supply when cooling water temperature is at or lower than the dew point for local

atmospheric conditions. Condensation on cooling water lines inside the power supply can cause severe damage.

Refer to Section 2.4.4 for additional details.

Cleaning

Do not submerge instrument. Clean only with a damp cloth and mild detergent on exterior surfaces only.

Moving and Handling

Four handles are provided for ease of moving and handling the Model 642. The handles can be used in place of

lifting lugs when cloth straps are used. Always use all four handles when moving the unit. Because of its weight, the

Model 642 should be handled by mechanical means. If for some reason it is necessary to move it by hand, a minimum

of two people is required.

CAUTION: To avoid injury to personnel, always observe proper lifting techniques in accordance with OSHA and

other regulatory agencies.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Introduction 1-9

Safety Summary (Continued)

1.4 SAFETY SYMBOLS

Number Symbol

None

Publication Description

IEC 417, No. 5031 Direct current

IEC 417, NO. 5032

IEC 417, No. 5033 Both direct and alternating current

IEC 617-2, No. 02-02-06 Three-phase alternating current

IEC 417, No. 5017 Earth (ground) TERMINAL

IEC 417, No. 5019 PROTECTIVE CONDUCTOR TERMINAL

IEC 417, No. 5020 Frame or chassis ground

IEC 417, No. 5021 Equipotentiality

IEC 417, No. 5007 On (supply)

IEC 417, No. 5008 Off (supply)

IEC 417, No. 5172 DOUBLE INSULATION OR REINFORCED

Bcakground color-yellow Caution, risk of electric shock

Background color-yellow Caution, hot surface

Background color-yellow Caution (refer to accompanying documents)

IEC 417, No. 5268-a In-position of bistable push control

IEC 417, No. 5269-a Out-position of bistable push control

IEC 1010-1 Fuse

Alternating current

Equipment protected by

INSULATION

ISO 3864, No. B.3.6

IEC 417, No. 5041

ISO 3864, No. B.3.1

Symbol and outline-black

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

1-10 Introduction

This Page Intentionally Left Blank

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Magnet System Design 2-1

CHAPTER 2

MAGNET SYSTEM DESIGN,

INSTALLATION, AND OPERATION

2.0 GENERAL

This chapter provides the user insight into the design, installation, and operation of a typical electromagnet. For

information on how to install the Model 642 please refer to Chapter 3. For Model 642 operation information, refer to

Chapter 4.

2.1 INTRODUCTION

A magnet used with the Model 642 Power Supply is typically an iron pole, twin coil, 4-inch pole diameter, variable air

gap, water cooled electromagnet. Larger magnets can be used depending on their electrical parameters and the magnetic

field requirements. The electromagnet provides a uniform magnetic field in the air gap between two adjustable poles.

The samples, which are to be tested for their magnetic properties, are placed in the air gap with appropriate monitoring

equipment attached. By varying the polarity and intensity of the field, useful data can be collected. A typical

electromagnet is shown in Figure 2-1.

Figure 2-1. A Typical Electromagnet

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

2-2 Magnet System Design

2.2 MAGNET CONSTRUCTION

The magnet consists of two water-cooled coils surrounding adjustable iron poles, which are fitted into an iron frame.

The frame supports the poles and coils, and improves the magnet’s efficiency. The iron poles are fitted with adjusting

mechanisms so that the air gap width can be set. Lock mechanisms are provided to hold the poles in place after

adjustment is made. The poles faces have pole caps attached, which provide the desired magnetic focus. The size and

shape of the pole caps are chosen according to the size of sample being tested and the magnetic field requirement.

2.3 CONNECTING THE MAGNET

Connecting the magnet to the power supply requires three separate circuits: the cooling water hoses, the main high

current power lines, and the safety switches which may include any combination of temperature and flow switches.

These connections are shown below.

2.3.1 Water Hose Connection

Water-cooling is essential for these magnets. The power dissipated can raise the temperature of the coils to the point

where they will be destroyed. In addition, the samples being tested may exhibit changes in their magnetic performance

with changes in temperature causing errors in the collected data. Typical water connection is shown in Figure 2-2. The

magnets may be supplied with hose barbs or standard hose fittings. The coils are connected in parallel so that the water

temperature rise is the same for both. Every effort should be made to insure that the flow rate in both coils is the same.

The minimum flow required is usually specified by the magnet vendor.

HOSE CLAMP

HOSE BARB FITTING

MAGNET WATER CONNECTION

REENFORCED HOSE

WATER FILTER

WATER VALVE

TEE

OPTIONAL FLOW SWITCH

MAGNET COIL

HOSE BARB FITTING

HOSE CLAMP

REENFORCED HOSE

Figure 2-2. Typical Magnet Water Hook-Up

2.3.2 Magnet Coil Wiring

Typical magnet coil wiring is shown in Figure 2-3. The connecting cable used should be of sufficient gage to prevent

excessive voltage drop and heat rise in the cable. The cables should be as short as possible to minimize the voltage drop.

Current carrying capacities for various sizes of cables and cable lengths are shown in Table 3-3. The connections must be

made with the correct size of hardware for the magnet terminal. We recommend the use of a spring or Belleville washer

for cable terminations. When the parts of a connection expand and contract with changes in temperature, they tend to

loosen. A spring washer will reduce this tendency.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Magnet System Design 2-3

POWER LEAD

CROSS CONNECTION WIRING

POWER LEAD

CROSS CONNECTION WIRING

BOLT

BELLEVILLE WASHER

CABLE CONNECTION

MAGNET POWER LUG

PLAIN WASHER

NUT

(PARALLEL WIRING)

(SERIES WIRING)

Figure 2-3. Typical Magnet Coil Wiring Showing Series and Parallel Connections

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

2-4 Magnet System Design

2.3.3 Temperature Switches and Flow Switches

As discussed in Section 2.3.1, water-cooling for the magnet is essential. To protect the magnet from damage resulting

from an interruption in cooling water, a flow switch, temperature switches or both should be installed. The switches must

have a normally closed contact, and if multiple switches are used, they must be connected in series. The switches are

then connected to the Flow Switch terminals of the Magnet Connector on the Model 642. The Model 642 monitors the

switches and if an open is detected, the output current is ramped to zero. (Flow switch monitoring depends on water

valve mode setting. See sections 4.12 and 4.13 for details.)Given the cost of the magnet, it is prudent to use both

temperature and flow switches. Some installations use two flow switches, one in the exhaust line of each coil so that if a

clog occurs in only one coil, it can be detected. Figure 2-4 shows the typical flow and temperature switch connection.

CAUTION: Care must be used in the selection of the flow switch. Some switches use a sensitive reed switch,

which can be overpowered by stray flux from the magnet and will not open when the magnet is

operating at high field. The flow switch must be tested by turning off the water while the magnet is

operating at full current.

THERMAL SWITCH

FLOW SWITCH

WATER VALVE

TO 642 MAGNET CONNECTOR VALVE CONTACTS

TO 642 MAGNET CONNECTOR FLOW SWITCH CONTACTS

INLET OUTLET

THERMAL SWITCH

Figure 2-4. Typical Thermal Switch, Flow Switch and Valve Wiring

2.3.4 Cooling Water and Water Valve

The cooling water for the magnet can be drawn from the municipal water facility or from a dedicated re-circulating water

chiller designed for this purpose. When water is drawn from the municipal water facility, the water should be turned on

only when it is required to reduce consumption and reduce the likelihood of scale build-up in the magnet. The water can

be turned on and off manually when the magnet is used, or automatically with a solenoid valve. The Model 642 provides

automatic control and a 24 VAC at 1 A output for this purpose. The optional water valve is shown in Figure 2-2. The

water inlet line should also be fitted with a sediment filter (not shown) to reduce scale build-up in the magnet coils and

connecting lines.

2.3.5 Grounding

A ground connection (tapped hole) is usually available at the rear of the electromagnet frame. This ground point is

provided for customers who would like to use the electromagnet frame as a signal ground or will be bringing hazardous

live voltages near the electromagnet and would like to make it an electrical safety ground. Please verify suitability for

such a function and compatibility with local and national electrical codes before making ground connections. Scrape off

excess paint near the connecting screw to ensure a good electrical contact with the bare steel of the electromagnet frame.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Magnet System Design 2-5

2.3.6 Final Check-Out

When all of the connections have been made the system should be tested to be sure it is operating correctly. The settings

for the magnet water should be checked to verify that they are correct for the configuration which has been installed

(Refer to Section 4.12 – Magnet Water). The maximum current setting for the magnet should be set also (Refer to

Section 2.4.2 and Section 4.11.1.)

2.4 ELECTROMAGNET OPERATION

This section provides a brief description of the typical operation of an electromagnet. For operation of the Model 642,

refer to Chapter 4.

2.4.1 Air Gap and Pole Caps

The first step in setting up a magnet for operation is to select the proper pole caps and adjust the air gap. These

parameters are determined by the size and shape of the sample, and the connections that must be made to the sample.

Generally, a smaller pole face provides a higher field within the air gap. A smaller air gap also provides a higher field.

The pole faces must be selected to accommodate the size of the sample being tested. The air gap is selected based on the

size of the sample and the other equipment being used. The curves for Field versus Current for various air gaps and pole

cap sizes for the Lake Shore Model EM4-HVA are shown in Figure 2-5. It also shows that these parameters are not

linear. This must be taken into account when operating an electromagnet. To obtain linearity, it is necessary to operate

the magnet and power supply under field control. (Refer to Section 2.4.4)

2.4.2 Maximum Current and Power

The Model 642 was designed to operate with a magnet load resistance of 0.50 Ω, but will work with a resistance range of

0.40 Ω to 0.60 Ω. The resistance of a magnet will rise with a rise in temperature and this should be taken into account.

The power dissipated in the magnet is given by: P=I2R. If the current remains constant, the power dissipated will rise

proportionately with the rise in resistance. The Model 642 allows the user to set a maximum current limit to prevent

damage to the magnet. (Refer to Section 4.11.1.)

Figure 2-5. Typical Curves of Field vs. Current for Various Air Gaps and Pole Cap Sizes (Sheet 1 of 3)

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

2-6 Magnet System Design

Figure 2-5. Typical Curves of Field vs. Current for Various Air Gaps and Pole Cap Sizes (Sheet 2 of 3)

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Magnet System Design 2-7

Figure 2-5. Typical Curves of Field vs. Current for Various Air Gaps and Pole Cap Sizes (Sheet 3 of 3)

2.4.3 Operation Under Field Control

To obtain a linear field ramp, a magnetic sensor such as a Hall probe is placed in the air gap along with the sample being

tested. The sensor is connected to a Gaussmeter. The output of the Gaussmeter is used to correct the programming input

to the power supply. In this way non-linearity can be corrected. Lakeshore manufactures probes and Gaussmeters for this

purpose.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

2-8 Magnet System Design

2.4.4 Avoiding Cooling Water Condensation

If the temperature of the cooling water is too cool relative to the air temperature and humidity, condensation can occur.

Condensation inside the power supply can cause severe damage. To avoid condensation, the power supply operator must

remain cognizant of the ambient air temperature, cooling water temperature, and the relative humidity. Lake Shore

defines the limits of these conditions as follows: ambient temperature = 18 – 28 °C (64 – 82 °F), cooling water

temperature = 15 – 25 °C (59 – 77 °F), and humidity = 20 – 80% (non-condensing). Knowing the actual state of these

conditions, the operator can calculate the dew point, or temperature at which condensation will occur. Tables 2-1 and 2-2

are included to aid in dew point calculation.

Table 2-1. Dew Point Calculation Table (In Degrees Celsius)

% Relative Humidity

°C 100 95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10

32 32 31 31 29 28 27 26 24 23 22 20 18 17 15 12 9 6 2 0

29 29 28 27 27 26 24 23 22 21 19 18 16 14 12 10 7 3 0 –

27 27 26 25 24 23 22 21 19 18 17 15 13 12 10 7 4 2 0 –

24 24 23 22 21 20 19 18 17 16 14 13 11 9 7 5 2 0 – –

21 21 20 19 18 17 16 15 14 13 12 10 8 7 4 3 0 – – –

18 18 17 17 16 15 14 13 12 10 9 7 6 4 2 0 – – – –

16 16 14 14 13 12 11 10 9 7 6 5 3 2 0 – – – – –

Table 2-2. Dew Point Calculation Table (In Degrees Fahrenheit)

% Relative Humidity

°F 100 95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10

90 90 88 87 85 83 81 79 76 74 71 68 65 52 59 54 49 43 36 32

85 85 83 81 80 78 76 74 72 69 67 64 61 58 54 50 45 38 32 –

80 80 78 77 75 73 71 69 67 65 62 59 56 53 50 45 40 35 32 –

75 75 73 72 70 68 66 64 62 60 58 55 52 49 45 41 36 32 – –

70 70 68 67 65 63 61 59 57 55 53 50 47 44 40 37 32 – – –

65 65 63 62 60 59 57 55 53 50 48 45 42 40 36 32 – – – –

60 60 58 57 55 53 52 50 48 45 43 41 38 35 32 – – – – –

Example: Determine the actual air temperature and relative humidity. Find the closest air temperature in the left-hand

column and the closest relative humidity across the top. If the air temperature is 24 °C (75 °F) and the relative humidity

is 35%, the intersection of the two shows a dew point of 7 °C (45 °F). Therefore, for the given conditions, the cooling

water must remain above 7 °C (45 °F) to prevent condensation.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Installation 3-1

CHAPTER 3

INSTALLATION

3.0 GENERAL

This chapter provides general installation instructions for the Model 642 Electromagnet Power Supply. CAUTION: To

ensure the best possible performance and maintain operator safety, read this entire chapter before installing the

instrument and applying power. Serious hazards can exist when an instrument of this power capacity is used incorrectly.

If you do not understand any section of this manual, consult Lake Shore for clarification. Lake Shore Cryotronics

assumes no responsibility for damage or injuries incurred due to improper installation, defeat of any of the safety

features or misuse of this power supply.

3.1 INSPECTION AND UNPACKING

Inspect shipping containers for external damage before opening them. Photograph any container that has significant

damage before opening it. If there is visible damage to the contents of the container, contact the shipping company and

Lake Shore immediately, preferably within 5 days of receipt of goods. Keep all damaged shipping materials and contents

until instructed to either return or discard them.

Open the shipping container and keep the container and shipping materials until all contents have been accounted for.

Check off each item on the packing list as it is unpacked. Instruments themselves may be shipped as several parts. The

items included with the Model 642 are listed below. Contact Lake Shore immediately if there is a shortage of parts or

accessories. Lake Shore is not responsible for any missing items if not notified within 60 days of shipment.

Inspect all items for both visible and hidden damage that occurred during shipment. If damage is found, contact Lake

Shore immediately for instructions on how to file a proper insurance claim. Lake Shore products are insured against

damage during shipment but a timely claim must be filed before Lake Shore will take further action. Procedures vary

slightly with shipping companies. Keep all shipping materials and damaged contents until instructed to either return or

discard them.

If the instrument must be returned for recalibration, replacement or repair, a returned goods authorization (RA) number

must be obtained from a factory representative prior to return. The Lake Shore RA procedure is given in Paragraph 7.2.

Items Included with Model 642 Electromagnet Power Supply:

1 – Model 642 Instrument

1 – Model 642 User’s Manual

2 – Front Handles (shipped attached)

2 – Rear Handles (shipped attached)

1 – Analog I/O Mating Connector

1 – Output Terminal Fasteners (set)

1 – Wiring Cover Plate and Screws

2 – 4 Pin Detachable Terminal Blocks

1 – 8 Pin Detachable Terminal Block

2 – Hose Clamps

1 – Output Lug Cover and Screws

3.1.1 Moving and Handling

Four handles are provided for ease of moving and handling the Model 642. The handles can be used in place of lifting

lugs when cloth straps are used. Always use all four handles when moving the Model 642. Because of its weight, the

Model 642 should be handled by mechanical means. If for some reason it is necessary to move it by hand, a minimum

of two people is required.

CAUTION: To avoid injury to personnel, always observe proper lifting techniques in accordance with OSHA

and other regulatory agencies.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

3-2 Installation

3.2 REAR PANEL DEFINITION

This paragraph defines the rear panel of the Model 642. Refer to Table 3-1. Readers are referred to paragraphs that

contain installation instructions and connector pin-outs for each feature.

CAUTION: Verify that the Model 642 has been set up for the proper line voltages.

CAUTION: Make rear panel connections with the instrument power off.

Table 3-1 below highlights the connections to be made on the rear panel. Figure 3-1 shows the rear panel and identifies

the connectors.

Table 3-1. Rear Panel Connector Identification

1 VOLTAGE

SELECTION 16 DIN terminals are provided behind a wiring cover to facilitate setting the correct input

voltage.

2 CIRCUIT

BREAKER An adjustable current auto-resetting circuit breaker is provided behind a wiring cover to

protect main power circuits.

3 FUSES ¼ A Class CC fuses (2) are provided behind a wiring cover to protect the start-up circuit.

4 CABLE ENTRY A 34 mm (1.3 inch) hole is provided for power cable entry and strain relief bushing.

5 POWER

TERMINALS Four DIN terminals are provided behind a wiring cover for connection of power wiring.

6 MAGNET

CONNECTOR A 4-pin detachable screw terminal block is provided to connect the optional magnet

water valve power and temperature and/or flow switch.

7 AUXILIARY

CONNECTOR An 8-pin detachable screw terminal block is provided to connect the optional Emergency

Stop, Remote Fault Indicator, Remote Enable and Chassis Ground.

8 POWER SUPPLY

CONNECTOR A 4-pin detachable screw terminal block is provided to connect the optional power

supply water valve power and/or flow switch.

9 COOLING

WATER Two 10 mm (3/8”) hose barbs are provided for input and output of cooling water.

10 OUTPUT

TERMINALS Two output lugs are provided for the magnet cable connections. Refer to Paragraph 3.8

and Figures 3-13 and 3-14 for connecting the magnet cables to the instrument.

11 ANALOG I/O A 15-pin D subminiature connector provides output for current and voltage monitoring,

as well as analog programming input. Refer to Paragraph 3.9 and see Figure 7-7.

12 RS-232C (DTE) A 9-pin D subminiature plug wired in DTE configuration is provided for use with RS-

232C serial computer interface. Refer to Paragraph 5.2.2 and see Figure 7-11.

13 IEEE-488

INTERFACE An IEEE-488 compliant interface connector is provided for use with IEEE-488 parallel

computer interface. Refer to Paragraph 5.1 and Figure 7-12.

14 CHASSIS

CONNECTION An earth safety chassis connection is provided to facilitate connection to the magnet

frame if noise problems exist.

15 DETACHABLE

HANDLES Two high-strength detachable handles are provided to aid in handling and lifting.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Installation 3-3

87610

159

14 1315

Figure 3-1. Model 642 Rear Panel (shown with wiring cover removed)

3.3 POWER WIRING AND SET-UP

This section describes how to properly connect the Model 642 to the line power. Please follow these instructions

carefully to ensure proper operation of the instrument and the safety of operators.

3.3.1 Line Voltage Selection

The Model 642 has four AC line voltage configurations covering seven different input voltages. The nominal voltage and

voltage tap setting as well as the circuit breaker current setting for each configuration is shown in Table 3-2. Verify that

the unit is configured correctly for the voltage being applied to the unit before applying power.

Table 3-2. Voltage and Current Selection

Nominal

Voltage Voltage

Tap Circuit

Breaker

200 V 204 V 18 A

208 V 204 V 18 A

220 V 225 V 17 A

230 V 225 V 17 A

380 V 380 V 12 A

400 V 408 V 12 A

415 V 408 V 12 A

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

3-4 Installation

Line Voltage Selection (Continued)

Changing line voltage is accomplished by moving four wires to the required voltage terminals. The required location is

shown in Figure 3-2. To change the voltage setting, loosen the four terminal screws in the voltage-change terminal block

to which the wires are connected and move the wires to the required voltage position. The wires are held in place in a

locator card to maintain their spacing and prevent mis-wiring. The screws in the new terminal location must be loosened

four full turns to allow the entry of the wires. Move all four wires at once by lifting the locator card to extract the wires

from the terminals. Move the card and wires to the correct location and insert the wires completely so that the card rests

against the terminals. While holding the locator card in place to keep the wires fully inserted, tighten the terminal screws.

The recommended torque requirement is 0.5 Nm. Also, tighten the four terminals where the wires were previously.

TERMINAL SCREW

WIRE FERRULE

VOLTAGE SELECTOR CARD

VOLTAGE INDICATOR KEY

Figure 3-2. Voltage Change Detail

3.3.2 Circuit Breaker Setting

The circuit breaker is an important safety feature of the Model 642. The required current setting depends on the voltage

for which the unit is wired. (Refer to Table 3-2.) Verify that the circuit breaker is set correctly for the line voltage being

applied to the unit. To set the breaker trip current, open the access cover on the circuit breaker and adjust the current

setting dial to the correct value. (See Figure 3-3.)

NOTE: The circuit breaker has an automatic reset feature. If the breaker trips, it will reset within a few minutes and

the unit can be restarted. If the units trips again after a short time, the trip current may be set incorrectly.

CURRENT SETTING DIALACCESS COVER

Figure 3-3. Circuit Breaker

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Installation 3-5

3.3.3 Start-up Fuses

The start-up transformer and associated circuitry are energized whenever the power is connected. To protect this

circuitry, two ¼ A, class CC fuses are provided. A fuse is accessed by pulling open the access door on the fuse holder as

shown in Figure 3-4. The fuses are inserted small-end first as shown.

Figure 3-4. Fuses

3.3.4 Cable Entry

A 34 mm (1.3 inch) diameter hole is provided for the power cable to enter the unit. A bushing is provided which will

accommodate a 16-19 mm (0.62-0.75 in) round neoprene jacketed cable (See Chapter 6). If a different cable is used, a

strain relief of the appropriate type and size must be provided by the installing agency.

CAUTION: Failure to install a strain-relief bushing is a hazard and could cause injury or death to operating

personnel in the event of a fault. Lake Shore reserves the right to void the warranty of any instrument not properly

installed.

A typical cable entry with bushing is shown in Figure 3-5.

BUSHING BODY

COMPRESSION GROMMET

SLIP WASHER

COMPRESSION COLLAR

CABLE

642 REAR PANEL

LOCKING RING

CONDUIT BUSHING

Figure 3-5. Typical Cable Entry with Bushing

3.3.5 Power Input Terminals

The Model 642 requires a 4 conductor power cord (not included). The input to the Model 642 is wired in a delta

configuration, but will operate from a delta or wye source. If operating from a wye source, the neutral line (N) is not

used. The ground (the green/yellow ground terminal) connects the instrument chassis to the electrical ground (safety

ground), and is required to prevent fault conditions which may be hazardous to operating personnel. In no case should

the safety ground line be omitted. In no case should a neutral line be used as a safety ground. If a detachable cord is used,

always plug the power cord into a properly grounded receptacle to ensure safe operation of the instrument. All wiring

must comply with the code requirements of the locality in which the instrument is installed. Figure 3-6 shows typical

input wiring. The wire ferrules shown are not required, but are recommended to prevent stray strands from shorting to

adjacent terminals.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

3-6 Installation

POWER CABLE

STRIP 13mm (0.5 in)

WIRE FERRULE (OPTIONAL)

POWER TERMINALS

140 mm (5.5 in)

Figure 3-6. Typical Power Input Wiring

3.3.6 Wiring Cover

When the power wiring, voltage setting and current setting are complete, install the wiring cover with the six (6)

6-32 × 3/8 screws provided. The wiring cover installation is shown in Figure 3.7. Be sure that the voltage indicator tab

of the voltage locator card (Figure 3.2) shows through the correct indicator slot in the wiring cover.

WARNING: Do not connect power or attempt to operate the unit with this cover removed. Lethal voltage and

currents exist inside. There is a risk of injury or death if an operator or technician comes in contact

with these potentials.

CHASSIS

WIRING COVER

6-32 X 3/8 SCREW

(6)

POWER CORD

VOLTAGE INDICATOR SLOTS

Figure 3-7. Wiring Cover Installation

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Installation 3-7

3.3.7 Mains Wiring

No cord or disconnecting plug is provided with the unit. In all cases, the field connection of the mains wiring shall

comply with all local wiring codes where the Model 642 is installed. The power source shall be protected with a

dedicated circuit breaker or fuse. The rating of the protection device shall be a value equal to that of the internal breaker

or the next higher commercially available value (See Table 3-2). If the Model 642 is connected with permanent wiring, a

disconnect switch shall be installed. The disconnect switch shall be located within 3 meters (10 feet) of the Model 642,

be clearly marked in layman’s language and be easily accessible.

3.4 MAGNET CONNECTOR

The magnet connector provides terminals for an optional magnet temperature switch or magnet water flow switch and an

optional magnet water control solenoid valve. The flow or temperature switch must have a normally closed contact rated

at 5 V at 10 mA. A contact closure is required to enable the Model 642 output. If a switch is not used, a jumper is

required. 24 VAC at 1 A is provided to operate a solenoid water valve for the magnet. This output is controlled by the

power supply, either automatically via software, or manually through the Magnet Water menu.

Water control is desirable to reduce water consumption when the water comes from a municipal facility. Turning the

water off when it is not required also reduces the probability of condensation on the magnet or connecting hoses. If the

cooling water comes from a facility chiller system, condensation is not usually a problem and a control valve is not

required. In this case, it is appropriate to install a flow switch (optional) or temperature switch (optional) to monitor the

water flow and protect the magnet in the event of a water flow interruption. Figure 3-8 shows examples of typical

magnet connector wiring.

NO VALVE OR SWITCH VALVE ONLY SWITCH ONLY VALVE AND SWITCH

Figure 3-8. Typical Magnet Connector Wiring

3.5 AUXILIARY CONNECTOR

The Auxiliary connector provides terminals for an emergency stop, contacts for a remote alarm, remote enable and a

chassis connection. The Emergency Stop must have a normally closed contact rated at 24 V at 1 A. When the contact is

opened, it turns off the Model 642. If an Emergency Stop switch is not used, a jumper is required. A normally closed or

normally open contact is provided to control a remote alarm annunciator. This set of contacts is rated at 30 V, 1 A. If it is

desirable to have a remotely located alarm to echo the internal alarm, these contacts can be used with an external power

source and external alarm. The Remote Enable switch must have a normally closed contact rated at 5 V at 10 mA.

contact closure is required to enable the Model 642 output. If a remote enable switch is not used, a jumper is required.

Figure 3-8 shows some typical auxiliary connector wiring. A chassis terminal is provided in the event that any of the

wires require a shield to minimize noise. Figure 3-9 shows some typical Auxiliary Connector wiring.

NO SWITCHES EMERGENCY STOP

REMOTE ENABLE

ALARM CONTACTS

TO REMOTE ALARM CIRCUIT

Figure 3-9. Typical Auxiliary Connector Wiring

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

3-8 Installation

3.6 POWER SUPPLY CONNECTOR

The Power Supply connector provides terminals for an optional water flow switch and an optional cooling water control

solenoid valve. The flow switch must have a normally closed contact rated at 5 V at 10 mA contact closure is required to

enable the Model 642 output. If a switch is not used, a jumper is required. 24 VAC at 1 A is provided to operate a water

control solenoid valve for the power supply cooling water. This output is controlled by the power supply, either

automatically via software, or manually through the Internal Water menu.

Water control is desirable to reduce water consumption when the water comes from a municipal facility. Turning the

water off when it is not required also reduces the probability of condensation within the power supply and connecting

tubing. If the cooling water comes from a facility chiller system, condensation is not usually a problem and a control

valve is not required. Figure 3-10 shows some typical Power Supply Connector wiring.

NO VALVE OR SWITCH VALVE ONLY SWITCH ONLY VALVE AND SWITCH

Figure 3-10. Typical Power Supply Connector Wiring

3.7 COOLING WATER

Two 10 mm (0.38 in) hose barbs are provided to connect to cooling water. The connection to the cooling water source

should be made with two 10mm (3/8 in) I.D. fiberglass reinforced hoses and two 20mm (25/32 in) adjustable hose

clamps. In addition, we recommend the installation of a sediment filter in the input line. A typical water hose connection

is shown in Figure 3-11.

The cooling water must be clean and free from sediment, salt and other contaminants, which might clog or erode the

water fittings. A minimum flow rate of 5.7 L (1.5 gal) per minute is required with a minimum pressure of 34 kPa (5 psi)

and a maximum pressure of 552kPa (80 psi). The temperature must be kept above 15˚C to avoid condensation and below

30˚C to ensure adequate system cooling. If water is drawn from a local municipal water source, the optional water valve

should be installed for economy and to prevent condensation (See 3.6 Power Supply Connector). If water is supplied by

a facility chiller, a valve can still be used but is not required.

CAUTION: Dot use de-ionized water because it is corrosive to the water fittings inside the Model 642.

HOSE BARB FITTING

ON BACK PANEL OF 642 ADJUSTABLE HOSE CLAMP

REINFORCED HOSE

Figure 3-11. Typical Water Hose Connection

Figure 3-12 shows the connections required when a water valve is used. The optional solenoid water valve is supplied

mounted to a bracket which mounts to the rear of the Model 642 as shown in Figure 3-12. Hose connections are made as

shown in Figure 3-11.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Installation 3-9

SOLENOID VALVE

WITH MOUNTING BRACKET

ADJUSTABLE HOSE CLAMP

REINFORCED HOSE

230 mm (9 in) LONG

Figure 3-12. Water Valve Connection

3.8 MAGNET CABLE CONNECTIONS

Magnet cable connections are made at the OUTPUT + and – terminals on the rear panel. These plated copper bus bars

accommodate M6 (¼ inch) mounting hardware. Two ¼-20 bolts, nuts, and Belleville washers are provided. Use load

wires heavy enough to limit the voltage drop to less than 0.5 volts per lead. This ensures proper regulation and keeps the

cables from overheating while carrying the required output current. Table 3-3 lists the current capacity and lead lengths

for load connections. Lake Shore sells magnet cables in 10 and 20 foot lengths. Refer to Paragraph 6.2 for ordering

accessories.

Figure 3-13 shows how the output cables are connected to the Model 642. A plain washer and a spring or Belleville

washer are provided. The Belleville washer is required to maintain contact pressure through varying material thickness

due to heating. The magnet leads should be dressed straight down to allow the installation of the protective lug cover.

Lug cover installation is shown in Figure 3-14.

Table 3-3. Current Capacity and Total Lead Lengths

Distance to Magnet

AWG Area

(mm2) Capacity

(A) Resistivity

/1000 feet Max Output of 70 A

0 53.5 245 0.09827 22 M (72 ft)

2 33.6 180 0.1563 14 M (45ft)

4 21.2 135 0.2485 8.5 M (28 ft)

6 13.3 100 0.3951 5.5 M (18 ft)

8 8.4 75 0.6282 3.4 M (11 ft)

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

3-10 Installation

BELLEVILLE WASHER

BOLT

OUTPUT LUG

MAGNET CABLE

PLAIN WASHER

NUT

Figure 3-13. Output Cable Connection

LUG COVER

38 mm (1.5 in) MOUNTING SCREWS

Figure 3-14. Output Lug Cover Installation

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Installation 3-11

3.9 ANALOG INPUT/OUTPUT CONNECTIONS

The Analog I/O connector provides connections to analog signals used to monitor or control the power supply. A Current

Program input is provided to control the current output. Two outputs are also provided to monitor the output current and

the output voltage. The connector and pin-out table is shown in figure 3-15. Specific information on each function is

provided in paragraphs 3.9.1 and 3.9.2.

815

Pin Name Pin Name

Chassis

Current Program –

Chassis

Voltage Monitor –

Chassis

Current Monitor –

Chassis

Current Program +

Chassis

Voltage Monitor +

Chassis

Current Monitor +

Figure 3-15. Model 642 Analog Input/Output Connector

3.9.1 External Current Programming

The output current can be programmed externally using an AC or DC voltage. This programming voltage can also be

summed with the internal current setting or ramp. Refer to Paragraph 4.15 to change the external current program mode.

The external current programming input is a differential input with a sensitivity of 10 V = 70 A and an input impedance

of > 50 kΩ. The programming voltage is limited internally to approximately ±10.1 V (Category 1) but care must be taken

to insure that maximum current capability of the magnet is never exceeded.

3.9.2 Output Current and Voltage Monitors

The output current and output voltage of the power supply can be monitored externally using the monitor output

connections on the Analog I/O connector. Each output is a buffered, differential, analog voltage representation of the

signal being monitored. The current monitor has a sensitivity of 7 V = 70 A and the voltage monitor has a sensitivity of

3.5 V = 35V. Both outputs have a source impedance of 20 Ω.

3.10 COMPUTER INTERFACE

The Model 642 can be programmed externally with a computer. Both RS-232C and IEEE-488 ports are provided.

3.10.1 RS-232C Interface Connection

An RS-232C port has been provided to allow remote computer control of the power supply. (Refer to Chapter 5,

Computer Interface Operation)

3.10.2 IEEE-488 Interface Connection

An IEEE-488 port has been provided to allow remote computer control of the power supply. (Refer to Chapter 5,

Computer Interface Operation)

3.11 CHASSIS CONNECTION

A 6-32 screw has been provided for attaching an optional chassis ground connection. This connection is normally not

required. However, occasionally there are noise problems associated with a floating magnet or other ancillary equipment.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

3-12 Installation

3.12 DETACHABLE HANDLES

The Model 642 is supplied with 4 detachable handles to enable handling. The handles should normally remain attached

to the unit. However, in some cases it may be necessary to remove the handles to enable mounting in an equipment rack.

In this case, handles may be removed but they should be stored in the rack with the power supply so that they may be

reattached if the unit must be returned for service. Heavy duty handles have been installed to carry the weight of the

power supply. No substitutions should be made. Light duty handles may fail when moving the supply causing the risk of

injury to personnel and damage to equipment.

3.13 RACK MOUNTING

The Model 642 can be installed in a standard 19-inch rack mount cabinet and requires 311 mm (12.25 in) (7U) in height.

At least 25 mm (1 in) of space should be provided on each side for cross ventilation. No ventilation panels are required

above or below the unit. Due to the weight of the power supply, it is recommended that the supply be located at the

bottom of the rack and that it rest on the bottom panel of the rack. If the rack does not have a bottom panel, a shelf,

capable of supporting 74 kg (163 lb) must be provided. Light duty support rails, which bolt to the sides of the front and

rear mounting rails of the rack are not strong enough to support this unit.

In addition, if the equipment rack which houses the Model 642 is to be shipped, the Model 642 must be anchored to the

shelf. Threaded inserts are provided in the bottom of the Model 642 for this purpose. Four (4) ¼-20 × ½ in bolts (not

included) are required. The hole pattern for mounting is shown in Figure 3.16.

CAUTION: The front panel rack mount is to be used only to secure the power supply to the front of the rack.

The bottom of the rack or the equipment shelf must support the entire weight of the supply. Do NOT

attempt to support the supply from the front mounting holes alone.

Figure 3-16. Mounting Hole Pattern

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Operation 4-1

CHAPTER 4

OPERATION

4.0 GENERAL

This chapter provides operating instructions for the features of the Model 642 Electromagnet Power Supply. Computer

interface instructions are in Chapter 5.

4.1 TURNING POWER ON

Verify that the AC line voltage indicator on the rear panel of the unit shows the appropriate AC line voltage before

turning the instrument on. The instrument may be damaged if it is turned on with the incorrect voltage selected.

Instructions for checking line voltage selection are given in Paragraph 3.3.1.

CAUTION: Be sure the unit is connected to an appropriate load before applying power.

Note: The Model 642 will not turn on if an Emergency Stop Switch is not connected or a jumper is not put in its

place on the “Auxiliary” connector at the rear of the unit. The unit will not turn on if it is connected to a

voltage source more than 10% greater than the voltage for which it is configured.

The power ON and OFF buttons are located in the lower left corner of the front panel. Press the ON button to energize

the Model 642. The Model 642 can be de-energized by pressing the OFF button, by pressing an optional remote

Emergency Stop button, or by the Model 642 software when a hazardous fault condition is detected. The ON and OFF

buttons are illustrated in Figure 4-1.

POWER "ON" BUTTON

POWER "OFF" BUTTON

Figure 4-1. Model 642 Power Push Buttons

When the Model 642 is turned on, the display shows the Lake Shore logo and the alarm beeper sounds briefly. After a

few seconds, a “Checking Hardware” message will appear in the center of the logo display while the instrument does an

internal diagnostic and makes sure everything is working. Most of the instrument setup parameter values are retained

when power is off with a few exceptions. The output current will always be set to 0 A anytime the instrument is powered

up. When the instrument is powered on for the first time, parameter values are set to their defaults, as listed in Table 4-3.

When initialization is complete, the instrument will begin its normal reading cycle. Current and voltage readings should

appear on the display. Any error messages will appear in the center of the display. Messages listed in Table 7-2,

Instrument Hardware Errors, are related to the instrument hardware and may require help from Lake Shore service. The

messages listed in Table 7-3, Operational Errors, are related to instrument operation and may be corrected with user

intervention.

The Model 642 should be allowed to warm up for a minimum of 30 minutes to achieve rated accuracy.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

4-2 Operation

4.2 DISPLAY DEFINITION

The Model 642 has an 8 line by 40 character vacuum fluorescent (VF) display capable of showing both text and graphic

images. The features displayed during normal operation include current measurement, voltage measurement, current

programming, ramp rate, magnet water status, internal water status, program mode, and internal temperature. Other

display configurations appear during parameter setting and data entry operations. These displays are illustrated in their

individual operation paragraphs. A typical display is shown below.

Output I Output V

+70.0000 A +35.000 V

Set: +70.0000 A Rate:0.0001 A/s

Magnet Water: Off Pgm Mode: Internal

Int Water: Off Int Temp: 27.5 ±C

4.3 LED ANNUNCIATORS

There are five LED annunciators on the front panel that are used to indicate the status of the instrument. These provide

easy verification of the operation of the instrument. See Figure 4-2 for LED locations.

Table 4-1. Model 642 LED Descriptions

Fault On when a hardware fault condition exists, blinking when a soft fault condition exists.

Compliance On when maximum compliance voltage is reached.

Power Limit On when power in internal devices reaches the maximum limit.

Ramping On when output current is ramping, blinking when ramp is paused.

Remote On when instrument is in remote computer interface mode.

4.3.1 Fault LED

The Fault LED will light whenever an error condition is encountered. It may also be accompanied by an alarm depending

on the fault. (Refer to Table 7-2 Instrument Hardware Errors, and Table 7-3 Operational Errors.)

4.3.2 Compliance LED

The Compliance LED lights whenever the maximum output voltage is reached. This can happen when attempting to

rapidly ramp a magnet with higher than usual voltage required to overcome the magnet’s inductance. The led will go out

when the condition clears.

4.3.3 Power Limit LED

The Model 642 has a hardware power limit to protect the internal power MOSFETs. If the power supply is driving a load

which has a resistance lower than the supply’s rated minimum, the power required may be higher than the devices can

safely handle. If this happens, the power in the devices is prevented from exceeding the safe limit and the Power Limit

LED will light to alert the operator to the condition. The led will go out when the condition clears.

4.3.4 Ramping LED

The Ramping LED lights whenever the internal control circuitry is changing the output current. When the ramp is

completed and the current is at the desired point, the LED goes out. The LED does not light when the output current is

being controlled by an external source.

4.3.5 Remote LED

The Remote LED is lit when the Remote key has been pressed to accept remote computer programming input, or upon

receiving the first command over the IEEE bus. When the LED is lit, the main keypad is locked out. Pressing the Local

key will return the unit to the local mode and reestablish keypad functions.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Operation 4-3

4.4 KEYPAD DEFINITION

The Model 642 has 22 keys separated into 3 groups on the instrument front panel. The sixteen keys in the center of the

grouping combines instrument setup and data entry. The keys below control the output current and ramping. The keys to

the right control the computer interface mode of the instrument. See Figure 4-2 for key locations. Refer to Table 4-2 for

keypad descriptions.

Figure 4-2. Model 642 Keypad and LED Layout

Table 4-2. Model 642 Key Descriptions

Magnet Water Selects the magnet water setup menu. Refer to Paragraph 4.12.

Internal Water Selects the internal water setup menu. Refer to Paragraph 4.13.

Display Setup Sets the display brightness. Refer to Paragraph 4.5.

Escape Exits from parameter setting sequence without changing the parameter value. Press and hold to

reset parameters to default values. Refer to Paragraph 4.18.

External Program Setup the external current programming mode. Refer to Paragraph 4.15.

Computer Interface Setup RS-232C and IEEE-488 computer interfaces. Refer to Paragraph 4.17.

Ramp Segments Setup ramp segment values. Refer to Paragraph 4.8.

Max Settings Setup maximum setting limits for output current, and ramp rate. Refer to Paragraph 4.11.

Status Displays a summary of the instrument status. Refer to Paragraph 4.14.

Enter Accepts a new parameter value. Press and hold to lock keypad. Refer to Paragraph 4.16.

0-9, ±, . Numeric data entry within a setting sequence.

H (Up) Increments a parameter selection or value.

I (Down) Decrements a parameter selection or value.

Output Setting Sets the output current. Refer to Paragraph 4.6.

Ramp Rate Sets the output current ramp rate. Refer to Paragraph 4.7.

Pause Ramp Pauses the output ramp and holds the current where it was pause pressed. Press again to

continue ramp. Refer to Paragraph 4.9.

Zero Output Ramps the current to 0 A at the programmed ramp rate. Refer to Paragraph 4.10.

Remote Places the instrument to Remote mode. Refer to Paragraph 5.1.2.

Local Returns the instrument to Local mode if in Remote. Refer to Paragraph 5.1.2.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

4-4 Operation

4.4.1 General Keypad Operation

The Model 642 uses three basic keypad operations, direct operation, setting selection, and data entry, for the majority of

operator interface. A few specialized keypad operations, such as ramp segment entry, are described in the individual

operation paragraphs.

Direct Operation: Key functions occur immediately when the key is pressed. Pause Ramp and Zero Output and are

examples of keys that operate this way.

Setting Selection: Allows the user to select from a finite list of parameter values. During setting selection the H and I

keys are used to select a parameter value. Enter is used to accept the change and advance to the next parameter. Escape

will cancel the change to that parameter and return to the normal display. Setting selection screens always include the

message: “Select with HI”.

Data Entry: Allows the user to enter numeric parameter values using the data entry keys that are printed on the key tops.

Data entry keys include numbers from 0 to 9, ± sign, and decimal point. The labels printed above the keys describe the

key function during normal operation. When one of the keys is pressed and a data entry sequence is started, the keys

follow the data entry functions printed on the key tops. Once the correct parameter value is entered, press Enter to

accept the change and advance to next parameter. Pressing Escape once will clear the new value and restart the setting

sequence. Pressing Escape again will return to the normal display. Data entry screens always include the message:

“Enter a value for”.

Related setting selection and data entry sequences are often chained together under a single key. To skip over a

parameter without changing its value, press Enter before pressing an arrow or number key. To return to the normal

display in the middle of a setting sequence, press Escape before pressing an arrow or number key. Changes entered

before Escape is pressed are kept.

4.5 DISPLAY SETUP

The Display Setup allows the user to set the display brightness. The vacuum fluorescent (VF) display on the Model 642

has four brightness settings between 25% and 100% that can be changed from the front panel. The brightness setting

changes the entire VF display but does not affect the LED annunciators to the right of the display. Continuous use of the

instrument at 100% brightness will reduce the operating life of the display and brightness of 25%, the default setting, is

recommended for most applications. To change the display brightness, press Display Setup and the brightness setup will

appear.

Display Setup

Select With °®

Brightness: 25 %

Use the s or t key to select brightness, 25%, 50%, 75%, or 100%. Press Enter to accept the new selection and return

to the normal display. Press Escape to cancel the new selection and return to the normal display.

4.6 SETTING OUTPUT CURRENT

The main purpose of the Model 642 Electromagnet Power Supply is to supply a very precise and stable current to a

magnet load. Before setting output current, make sure that the instrument is properly setup for the magnet system

that is being used. This includes setting up the maximum output current and maximum ramp rate. When a new output

current setting is entered, the supply will ramp to the new setting at the current ramp rate, unless limited by the fixed

compliance voltage. The Ramping LED will be lit while the output current is ramping. When the output current setting is

entered, it will be limited in magnitude by the maximum current setting. Refer to Paragraph 4.11 to setup the maximum

settings.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Operation 4-5

Setting Output Current (Continued)

To change the output current setting, press the Output Setting key. The output current setting value on the normal

display will be highlighted to prompt for the new output current setting value.

Set: + 0.0000 A

Use the data entry keys to enter an output current setting value between –70.0000 and + 70.0000. Press Enter to accept

the new value. Press Escape to restart the setting sequence and enter a different value. Press Escape again to leave the

setting sequence.

NOTE: The output current setting value can be set as high as ±70.1000 A. This can be used to compensate for variances

in calibration. The output current is guaranteed to reach a minimum of 70 A into a 0.5 ohm load but may not be

able to reach 70.1 A in all circumstances.

The output current setting is not allowed to change if the instrument is setup so that the output current is programmed

solely by an external voltage. Refer to Paragraph 4.15 to setup the external current program mode.

Change not allowed while

in external current program mode

4.7 CURRENT RAMP RATE

The output current of the Model 642 will always ramp from one current setting to another. There is no way to turn off the

current ramping function, but if a very fast ramp rate is desired, a ramp rate as high as 99.999 A/s can be entered.

To change the current ramp rate press the Ramp Rate key. The ramp rate value on the normal display will be

highlighted to prompt for the new ramp rate value.

Rate: 1.0000 A/s

Use the data entry keys to enter the ramp rate value between 0.0001 and 99.999 A/s. Press Enter to accept the new

value. Press Escape to restart the setting sequence and enter a different value. Press Escape again to leave the setting

sequence.

4.8 RAMP SEGMENTS

The magnetic field produced by electromagnets is not linear with current setting. The best way to compensate for this is

to use closed loop field control but if absolute accuracy is not necessary than some of this nonlinearity can be corrected

by the use of the ramp segments feature. The ramp segments feature can be used to increase the current ramp rate as the

magnet saturates in an attempt to maintain the same field ramp rate. This feature can change the output current ramp rate

based on the output current setting. As the output setting ramps through the segment boundary, the new ramp rate will be

used although it will still be limited by the maximum ramp rate setting. Refer to Paragraph 4.11.2 to set the maximum

ramp rate.

To use the ramp segment feature, the ramp segments must be enabled and the ramp segment table must be setup to

specify which ramp rate to use for each current setting. The table should be setup in order of increasing current.

A current entry of 0 A indicates the end of the table and the instrument will not search any higher in the table.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

4-6 Operation

Ramp Segments (Continued)

To configure the ramp segments press Ramp Segments. The first ramp segments setup screen appears as a prompt for

the ramp segments mode.

Ramp Segments

Select With °®

Ramp Segments: Enable

Use the s or t key to select the ramp segments mode, either Enable or Disable. Press Enter to accept the new selection

and continue to the next setting screen. Press Escape to cancel the new selection and return to the normal display.

If the ramp segments are enabled, the next ramp segments screen that appears is for entering or editing the ramp

segments table. All five of the ramp segments are shown on the display at the same time. The segments should be

entered in order of increasing current. An entry of 0 A will indicate the end of the table and the instrument will not

search beyond that segment.

Ramp Segments

Current Ramp Rate

1: 10.0000 A 1.0000 A/s

2: 15.0000 A 0.8000 A/s

3: 20.0000 A 0.7000 A/s

4: 30.0000 A 0.6000 A/s

5: 40.0000 A 0.5000 A/s

When the segment number is highlighted, use the s or t key to scroll through the ramp segments. Press the Enter key

when the desired segment number is highlighted and continue to the current field.

When the current field is highlighted, use the numerical keypad to enter the upper current setting for that ramp segment

in amps. Press Enter to accept the new selection and continue to the ramp rate field. Press Escape to restart the setting

sequence and enter a new value. Press Escape again to highlight the segment number.

When the ramp rate field is highlighted, use numerical keypad to enter the applicable ramp rate in A/s. Press Enter to

accept the new selection and continue to the next segment. Press Escape to restart the setting sequence and enter a new

value. Press Escape again to highlight the segment number.

Similarly enter or edit all ramp segments. When complete, press the Escape key while the segment number field is

highlighted to exit the ramp segment edit screen and return to the normal display. When output current is called for using

the Output Setting key, the output will ramp to the desired current using the ramp segment set points.

4.9 PAUSE RAMP

The Pause Ramp key will pause the output current ramp within two seconds after the key is pressed. While the output

current ramp is paused, the Ramping LED will blink. Pressing the Pause Ramp key again will continue the ramping.

Pressing the Enter key while the ramp is paused will set the current at the paused setting and exit the Pause Ramp

mode.

4.10 ZERO OUTPUT

The Zero Output key on the front panel can be used to set the output current to 0 A. When the Zero Output key is

pressed, the current output will begin to ramp down using the current ramp rate. This key is equivalent to using the

Output Setting key and entering 0 A except that it works even when the Model 642 is being programmed externally.

Refer to Paragraph 4.6 to set the output current.

NOTE: The current ramp rate applies only to the internal current output setting. When the Model 642 is

programmed externally, the drop to zero output (when the Zero Output key is pressed) will be quite rapid

(~1 second) and limited primarily by the magnet reactance and the Model 642 voltage compliance limit.

The voltage compliance LED may light during the change.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Operation 4-7

4.11 MAXIMUM SETTING LIMITS

The Model 642 offers a maximum setting limit for output current and ramp rate. Typical properties of the magnet will

dictate these parameters. These maximum parameters should be entered before the magnet system is used to prevent

damage.

4.11.1 Maximum Output Current

Maximum Output Current limits the output current that can be entered. This setting will only limit the internal output

current setting. If the output current is being programmed by an external voltage, then some external provision must be

made to insure that the programming voltage will never exceed the desired output current. See Paragraph 4.15 to setup

the External Current Programming mode.

To set the maximum output current limit press Max Settings. The first maximum setting screen appears as a prompt for

the maximum output current limit.

Maximum Settings

Enter a Value For

Max Current: 60.0000 A

Use the data entry keys to enter the maximum output current limit value between 0.0000 and 70.0000 A. Press Enter to

accept the new value. Press Escape to restart the setting sequence and enter a different value. Press Escape again to

leave the setting sequence.

NOTE: The maximum output current limit value can be set as high as 70.1000 A. This can be used to compensate

for variances in calibration. The output current is guaranteed to reach a minimum of 70 A into a 0.5-ohm

load but may not be able to reach 70.1 A in all circumstances.

4.11.2 Maximum Current Ramp Rate

Maximum Current Ramp Rate limits the maximum current ramp rate that can be entered. This setting will only limit the

internal output current ramp setting. If ramp segments are being used, this setting will also limit the ramp rate that can be

set by a ramp segment. Refer to Paragraph 4.8 to setup Ramp Segments.

To enter a value for the maximum current ramp rate limit, continue from the maximum current screen or press Max

Settings then Enter until the following display setup screen appears as a prompt for the maximum current ramp rate

limit.

Use the data entry keys to enter the maximum current ramp rate limit value between 0.0001 and 99.999 A/s. Press Enter

to accept the new value. Press Escape to restart the setting sequence and enter a different value. Press Escape again to

leave the setting sequence.

Maximum Settings

Enter a Value For

Max Ramp Rate: 1.0000 A/s

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

4-8 Operation

4.12 MAGNET WATER

The Model 642 provides power to control an external magnet water solenoid control valve. The setup of the valve

control is available in the Magnet Water menu. The four menu selections are Auto, On, Off, and Disabled, with Auto

being the default setting.

In the Auto mode, the water valve will be energized when the power in the magnet exceeds 100 W. When the power

drops below 100 W, the valve will remain energized for an additional minute to remove any residual heat build-up.

In the On mode, the valve will be energized whenever the power supply is on. This feature can be used when the system

is first installed to purge air from the water lines and magnet. It can also be used to turn on the water in advance of a test

to bring the magnet temperature to equilibrium. The Off menu selection can be used to turn it off.

In the Disabled mode, the Model 642 assumes that no valve is installed and the line for Magnet Water status will not be

displayed.

The magnet water flow switch is monitored whenever the water valve is energized. It is also monitored continuously

when in Disabled mode to allow the use of a flow switch even when no water valve is used. If no flow switch or water

valve is present, then a jumper must be installed across the flow switch contacts for proper operation.

4.13 INTERNAL WATER

The Model 642 provides power to control an external water solenoid control valve to control the cooling water for the

power supply. The setup of the valve control is available in the Internal Water menu. The four menu selections are

Auto, On, Off, and Disabled, with Disabled being the default setting.

In the Auto mode, the water valve will be energized when the power in the internal power devices exceeds 100 W. When

the power drops below 100 W, the valve will remain energized for an additional minute to remove any residual heat

build-up.

In the On mode, the valve will be energized whenever the power supply is on. This feature can also be used when the

Model 642 is first installed to purge air from the lines. The Off menu selection can be used to turn it off.

In the Disabled mode, the Model 642 assumes that no valve is installed and the line for Internal Water status will not be

displayed.

The internal water flow switch is monitored whenever the water valve is energized. It is also monitored continuously

when in Disabled mode to allow the use of a flow switch even when no water valve is used. If no flow switch or water

valve is present, then a jumper must be installed across the flow switch contacts for proper operation.

4.14 ERROR STATUS DISPLAY

Error messages appear in the center of the instrument display when a problem is identified during operation. The Fault

LED will also light to indicate error conditions, blinking for operational errors, on continuously for instrument hardware

errors. Refer to Paragraph 7.6 for a listing of all the error conditions. When an error condition occurs, the name of the

error is shown in the display alternately with “Press Status Key for More Info.” Pressing the Status key will bring up a

screen that will show an extended description of the error.

To enter the error status display press Status while in the main display. A screen similar to the one shown below

appears. This screen will differ depending on the error that is being displayed. If there are no errors to report, the display

will show “No errors reported.” The following example shows the description for “External Current Program Error”.

Cannot set external current program mode.

Set programming voltage to 0 V or change to

internal program mode.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Operation 4-9

4.15 EXTERNAL CURRENT PROGRAMMING

The output current of the Model 642 can be set internally, externally, or by the sum of the external and internal settings.

Normally, the current is controlled internally by entering a setting from the front panel using the Output Setting key.

Refer to Paragraph 4.6 to set the output current. When the external program mode is set to External, the front panel

setting is fixed at 0 A and the output current is set using an external voltage where 10 V = 70 A. When the external

program mode is set to Sum, the internal and external settings are summed together to set the output current. When using

the External or Sum modes, care must be taken to insure that the output current does not exceed the maximum current for

the magnet. The software maximum setting limits cannot limit the output current or ramp rate that is set when using the

External or Sum modes. A –3 dB, 40 Hz, two-pole, low-pass filter limits the bandwidth of the external current

programming input. The bandwidth of the output is also limited by the compliance voltage and the inductance of the

magnet. To configure the external current program mode press External Program. The following setup screen appears

as a prompt for the external current program mode.

External Program Mode

Select With °®

External Program Mode: Internal

Use the s or t key to select the external current program mode, Internal, External, or Sum. Press Enter to accept the

new selection and return to the normal display. Press Escape to cancel the new selection and return to the normal

display.

To avoid discontinuities in the output current, the external current programming mode cannot be changed if the

programming voltage is not zero or the front panel current setting is not zero. If the external current program mode is

going to be kept from changing, an error box will pop up explaining why the new setting is being ignored. This error box

is shown below.

Change not allowed while

programming voltage is not zero.

4.16 LOCKING THE KEYPAD

The keypad lock feature prevents accidental changes to parameter values. When the keypad is locked, parameter values

may be viewed but cannot be changed from the front panel. The Model 642 has two keypad lock modes. The lock all

mode locks out changes to all parameters. The lock limits mode locks out changes to all of the parameters except Output

Setting, Ramp Rate, Zero Output and Pause Ramp. This allows the power supply to be operated without allowing any

changes to the power supply setup.

A 3-digit code must be used to lock and unlock the keypad. The factory default code is 123 and it can only be changed

using a computer interface. If the instrument parameters are reset to default values (See Default Parameter Values 4.18),

the code is reset to the factory default. The instrument parameters cannot be reset to default values from the front panel

when the keypad is locked.

The following message box appears on the display if the user attempts to change a parameter while the keypad is locked.

Change not allowed while

keypad is locked.

NOTE: The computer interface has a remote operation mode that may be mistaken for a locked keypad. If the front

panel Remote LED is lit, press the Local key to change to local control of the instrument.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

4-10 Operation

Locking the Keypad (Continued)

To lock or unlock the instrument keypad press and hold the Enter key for 5 seconds. The following setup screen appears

as a prompt for the keypad lock mode.

Keypad Lock

Select With °®

Keypad Lock: Unlock

Use the s or t key to select the keypad lock mode, Unlock, Lock All, or Lock Limits. Press Enter to choose the new

selection and continue to the keypad lock code verification. The change to the keypad lock mode is not made until the

correct keypad lock code has been entered. Press Escape to cancel the new selection and return to the normal display.

Once the keypad lock mode has been selected, the keypad lock code must be entered to accept the change. The following

screen appears as a prompt for the keypad lock code.

Keypad Lock

Enter A Value For

Keypad Lock Code:

Use the data entry keys to enter the 3-digit lock code (default 123). An asterisk will appear on the display for each

number entered. If the code entered matches the lock code, the display will show “Change Accepted” and the

keypad lock mode will be updated. If the code entered does not match the lock code, the display will show

“Invalid Lock Code” and the keypad lock mode will not change.

4.17 COMPUTER INTERFACE

There are two computer interfaces on the Model 642, a serial RS-232C interface and an IEEE-488 interface. These

interfaces are used to connect the instrument to a computer for automated control or data taking. Refer to Chapter 5.

4.17.1 Changing Serial Baud Rate

To select the Serial Interface Baud Rate press the Computer Interface key. The first computer interface screen appears

as a prompt for Baud.

Computer Interface

Select With °®

Baud: 9600

Use the s or t key to select 9600, 19200, 38400, or 57600 Baud. Default is 9600 Baud. Press Enter to accept the new

selection and continue to the next screen. Press Escape to cancel the new selection and return to the normal display.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Operation 4-11

4.17.2 Changing IEEE-488 Interface Parameters

Two interface parameters, address and terminators, must be set from the front panel before IEEE-488 communication

with the instrument can be established. Other interface parameters can be set via the interface using the device specific

commands provided in Paragraph 5.3.

To set the IEEE-488 parameters, press the Computer Interface key and press Enter to skip past Serial Interface Baud

Rate. The following computer interface screen appears as a prompt for the IEEE-488 address.

Computer Interface

Select With °®

IEEE Address: 12

Use the s or t key to select an address between 1 and 30. The default is twelve. Press Enter to accept the new

selection and continue to the next setting screen. Press Escape to cancel the new selection and return to the normal

display. The next computer interface screen appears as a prompt for the IEEE-488 terminators.

Computer Interface

Select With °®

IEEE Term: Cr Lf

Use the s or t key to select one of the following terminators: CR/LF, LF/CR, LF, and EOI. The default is CR/LF.

Press Enter to accept the new selection and continue to the next setting screen. Press Escape to cancel the new selection

and return to the normal display.

4.18 DEFAULT PARAMETER VALUES

It is sometimes desirable to reset instrument parameters to their default values. This data is stored in nonvolatile memory

called EEPROM. Instrument calibration is not affected by this operation. Firmware version information for the main

firmware and the DAC firmware is also displayed during this sequence.

To clear EEPROM memory or view the firmware versions press and hold the Escape key for 5 seconds. The following

screen appears to show the main firmware version, the DAC processor firmware version, and as a prompt for returning

the instrument parameters to default values. Default parameter values are listed in Table 4-3.

Main Code Version: 1.0

DAC Code Version: 1.0

Select With °®

Default Values: No

Use the s or t key to select Yes for default values and No to continue without changing the parameter values. Press

Enter to accept the new selection and return to the normal display. Press Escape to cancel the new selection and return

to the normal display.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

4-12 Operation

Table 4-3. Default Parameter Values

Output Settings

Output Current* .....................................0 A

Current Ramp Rate..................... 99.999 A/s

Maximum Settings

Max Output Current..........................70.1 A

Max Ramp Rate......................... 99.999 A/s

External Program Mode

External Program Mode.................. Internal

Ramp Segments

Ramp Segments .............................Disabled

Ramp Segments Current ........................0 A

Ramp Segments Rate ................. 1.0000 A/s

Display

Brightness ..............................................25%

Keypad Locking

State............................................... Unlocked

Lock Code............................................... 123

Computer Interface

Baud...................................................... 9600

IEEE-488 Address .................................... 12

IEEE-488 Terminators.......................CR/LF

Mode*.................................................. Local

Water Settings

Magnet Water................................ Disabled

Internal Water ............................... Disabled

* Indicates value is also initialized on power up

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Computer Interface Operation 5-1

CHAPTER 5

COMPUTER INTERFACE OPERATION

5.0 GENERAL

This chapter provides operational instructions for the computer interface for the Lake Shore Model 642 Electromagnet

Power Supply. Either of the two computer interfaces provided with the Model 642 permit remote operation. The first is

the IEEE-488 Interface described in Paragraph 5.1. The second is the Serial Interface described in Paragraph 5.2. The

two interfaces share a common set of commands detailed in Paragraph 5.3. Only one interface can be used at a time.

5.1 IEEE-488 INTERFACE

The IEEE-488 Interface is an instrumentation bus with hardware and programming standards that simplify instrument

interfacing. The Model 642 IEEE-488 Interface complies with the IEEE-488.2-1987 standard and incorporates its

functional, electrical, and mechanical specifications unless otherwise specified in this manual.

All instruments on the interface bus perform one or more of the interface functions of TALKER, LISTENER, or BUS

CONTROLLER. A TALKER transmits data onto the bus to other devices. A LISTENER receives data from other

devices through the bus. The BUS CONTROLLER designates to the devices on the bus which function to perform.

The Model 642 performs the functions of TALKER and LISTENER but cannot be a BUS CONTROLLER. The BUS

CONTROLLER is the digital computer which tells the Model 642 which functions to perform.

Below are Model 642 IEEE-488 interface capabilities:

• SH1: Source handshake capability.

• RL1: Complete remote/local capability.

• DC1: Full device clear capability.

• DT0: No device trigger capability.

• C0: No system controller capability.

• T5: Basic TALKER, serial poll capability, talk only, unaddressed to talk if addressed to listen.

• L4: Basic LISTENER, unaddressed to listen if addressed to talk.

• SR1: Service request capability.

• AH1: Acceptor handshake capability.

• PP0: No parallel poll capability.

• E1: Open collector electronics.

Instruments are connected to the IEEE-488 bus by a 24-conductor connector cable as specified by the standard. Refer to

Paragraph 7.12.2. Cables can be purchased from Lake Shore or other electronic suppliers.

Cable lengths are limited to 2 meters for each device and 20 meters for the entire bus. The Model 642 can drive a bus

with up to 10 loads. If more instruments or cable length is required, a bus expander must be used.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

5-2 Computer Interface Operation

5.1.1 Changing IEEE-488 Interface Parameters

Two interface parameters, address and terminators, must be set from the front panel before communication with the

instrument can be established. Other interface parameters can be set via the interface using the device specific commands

provided in Paragraph 5.3.

To set the IEEE-488 parameters, press the Computer Interface key and press Enter to skip past Serial Interface Baud

Rate. The following computer interface screen appears as a prompt for the IEEE-488 address.

Computer Interface

Select With °®

IEEE Address: 12

Use the s or t key to select an address between 1 and 30. The default is twelve. Press Enter to accept the new

selection and continue to the next setting screen. Press Escape to cancel the new selection and return to the normal

display. The next computer interface screen appears as a prompt for the IEEE-488 terminators.

Computer Interface

Select With °®

IEEE Term: Cr Lf

Use the s or t key to select one of the following terminators: CR/LF, LF/CR, LF, and EOI. The default is Cr/Lf. Press

Enter to accept the new selection and continue to the next setting screen. Press Escape to cancel the new selection and

return to the normal display.

5.1.2 Remote/Local Operation

Normal operations from the keypad are referred to as ‘Local’ operations. The Model 642 can also be configured for

‘Remote’ operations via the IEEE-488 interface or the Remote key. The Local key will take the instrument out of

‘Remote’ operation and place it in ‘Local’ operation. During ‘Remote’ operations, the Remote LED annunciator will be

illuminated and operations from the keypad will be disabled.

5.1.3 IEEE-488 Command Structure

The Model 642 supports several command types. These commands are divided into three groups.

1. Bus Control – Refer to Paragraph 5.1.3.1.

a. Universal

(1) Uniline

(2) Multiline

b. Addressed Bus Control

2. Common – Refer to Paragraph 5.1.3.2.

3. Device Specific – Refer to Paragraph 5.1.3.3.

4. Message Strings – Refer to Paragraph 5.1.3.4.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Computer Interface Operation 5-3

5.1.3.1 Bus Control Commands

A Universal Command addresses all devices on the bus. Universal Commands include Uniline and Multiline Commands.

A Uniline Command (Message) asserts only a single signal line. The Model 642 recognizes two of these messages from

the BUS CONTROLLER: Remote (REN) and Interface Clear (IFC). The Model 642 sends one Uniline Command:

Service Request (SRQ).

REN (Remote) – Puts the Model 642 into remote mode.

IFC (Interface Clear) – Stops current operation on the bus.

SRQ (Service Request) – Tells the bus controller that the Model 642 needs interface service.

A Multiline Command asserts a group of signal lines. All devices equipped to implement such commands do so

simultaneously upon command transmission. These commands transmit with the Attention (ATN) line asserted low.

The Model 642 recognizes two Multiline commands:

LLO (Local Lockout) – Prevents the use of instrument front panel controls.

DCL (Device Clear) – Clears Model 642 interface activity and puts it into a bus idle state.

Finally, Addressed Bus Control Commands are Multiline commands that must include the Model 642 listen address

before the instrument responds. Only the addressed device responds to these commands. The Model 642 recognizes four

of the Addressed Bus Control Commands:

SDC (Selective Device Clear) – The SDC command performs essentially the same function as the DCL command

except that only the addressed device responds.

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.

SPE (Serial Poll Enable) and SPD (Serial Poll Disable) – Serial polling accesses the Service Request Status Byte

command ends the polling sequence.

5.1.3.2 Common Commands

Common Commands are addressed commands which create commonalty between instruments on the bus. All

instruments that comply with the IEEE-488 1987 standard share these commands and their format. Common commands

all begin with an asterisk. They generally relate to “bus” and “instrument” status and identification. Common query

commands end with a question mark (?). Model 642 common commands are detailed in Paragraph 5.3 and summarized

in Table 5-8.

5.1.3.3 Device Specific Commands

Device specific commands are addressed commands. The Model 642 supports a variety of device specific commands to

program instruments remotely from a digital computer and to transfer measurements to the computer. Most device

specific commands perform functions also performed from the front panel. Model 642 device specific commands are

detailed in Paragraph 5.3 and summarized in Table 5-8.

5.1.3.4 Message Strings

A message string is a group of characters assembled to perform an interface function. There are three types of message

strings: commands, queries and responses. The computer issues command and query strings through user programs, the

instrument issues responses. Two or more command strings or queries can be chained together in one communication but

they must be separated by a semi-colon (;). The total communication string must not exceed 255 characters in length.

A command string is issued by the computer and instructs the instrument to either perform a function or change a

parameter setting. When a command is issued, the computer is acting as ‘talker’ and the instrument as ‘listener’. The

format is:

<command mnemonic><space><parameter data><terminators>.

Command mnemonics and parameter data necessary for each one is described in Paragraph 5.3. Terminators must be

sent with every message string.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

5-4 Computer Interface Operation

Message Strings (Continued)

A query string is issued by the computer and instructs the instrument which response to send. Queries are issued similar

to commands with the computer acting as ‘talker’ and the instrument as ‘listener’. The query format is:

<query mnemonic><?><space><parameter data><terminators>.

Query mnemonics are often the same as commands with the addition of a question mark. Parameter data is often

unnecessary when sending queries. Query mnemonics and parameter data if necessary is described in Paragraph 5.3.

Terminators must be sent with every message string. Issuing a query does not initiate a response from the instrument.

A response string is sent by the instrument only when it is addressed as a ‘talker’ and the computer becomes the

‘listener’. The instrument will respond only to the last query it receives. The response can be a reading value, status

report or the present value of a parameter. Response data formats are listed along with the associated queries in

Paragraph 5.3.

5.1.4 Status System

5.1.4.1 Overview

The Model 642 implements a status system compliant to the IEEE 488.2 – 1992 standard. The status system provides a

method of recording and reporting instrument information and is typically used to control the Service Request (SRQ)

interrupt line. A diagram of the status system is shown in Figure 5-1. The status system is made up of register sets, the

Status Byte register and the Service Request Enable register. Each register set consists of three types of registers,

condition, event, and enable,

5.1.4.1.1 Condition Registers

Each register set (except the Standard Event Register set) includes a condition register as shown in Figure 5-1. The

condition register constantly monitors the instrument status. The data bits are real-time and are not latched or buffered.

The register is read-only.

5.1.4.1.2 Event Registers

Each register set includes an event register as shown in Figure 5-1. Bits in the event register correspond to various

system events and latch when the event occurs. When an event bit is set, subsequent events corresponding to that bit are

ignored. Set bits remain latched until the register is cleared by a query command (such as *ESR?) or a *CLS command.

The register is read-only.

5.1.4.1.3 Enable Registers

Each register set includes an enable register as shown in Figure 5-1. An enable register determines which bits in the

corresponding event register will set the summary bit for the register set in the Status Byte. The user may write to or read

from an enable register. Each event register bit is logically ANDed to the corresponding enable bit of the enable register.

When an enable register bit is set by the user, and the corresponding bit is set in the event register, the output (summary)

of the register will be set, which in turn sets the summary bit of the Status Byte register.

5.1.4.1.4 Status Byte Register

The Status Byte register, typically referred to as simply the Status Byte, is a non-latching, read-only register that contains

all of the summary bits from the register sets. The status of the summary bits are controlled from the register sets as

explained above. The Status Byte also contains the Request for Service (RQS)/Master Summary Status (MSS) bit. This

bit is used to control the Service Request hardware line on the bus and to report if any of the summary bits are set via the

*STB? command. The status of the RQS/MSS bit is controlled by the summary bits and the Service Request Enable

5.1.4.1.5 Service Request Enable Register

The Service Request Enable Register determines which summary bits in the Status Byte will set the RQS/MSS bit of the

Status Byte. The user may write to or read from the Service Request Enable Register. Each Status Byte summary bit is

logically ANDed to the corresponding enable bit of the Service Request Enable Register. When a Service Request

Enable Register bit is set by the user, and the corresponding summary bit is set in the Status Byte, the RQS/MSS bit of

the Status Byte will be set, which in turn sets the Service Request hardware line on the bus.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Computer Interface Operation 5-5

Service Request

Name

Bit

Not

RQS = Service Request

MSS = Master Summary Status Bit

ESB = Event Status Sumary Bit

MAV = Message Available Summary Bit

OSB = Operation Summary Bit

OESB = Operational Error Summary Bit

HESB = Hardware Error Summary Bit

Used

COMP = Compliance

RAMP = Ramp Done

OPSTE?

Operation

Event Enable

OPSTE, Used

Not

Used

Not Used

Not

Used

Not Not

Used

*SRE, *SRE?

Enable Register

Operation

OPSTR?

Condition

OPST?

Operation

Event

Used

Not

Used

Not

Used

Not

Used

Not

Used

Not

Used

Not Used

Not

Used

Not

Used

OSB

AND

Bit

Name

210

AND

Name

Bit

Name

Bit

Not

Used

2 1

ESB

MAV

432

Used

Not

Bit

Name

Standard Event

Status Byte

Generate service

request. Reset by

Read by *STB?

PON = Power on

CME = Command Error

EXE = Execution Error

QYE = Query Error

OPC = Operation Complete

RQS

MSS

serial poll.

*ESE, *ESE?

Status Enable

*STB?

AND

OSB

RQS

AND

*ESR?

Standard Event

Status Register PON

AND

Not

Used

CME

EXE

Used

Not

Used

AND

MSS ESB

AND

MAV

Buffer

Output

Used

Not

Name

Bit

AND

Used

Not

QYE

210

OPC

2 of 2

Sheet

From

Used

Not

PON

Used

Not Used

Not

EXE

CME

QYE

NameOPC

0Bit

AND

PRLM = Power Limit

AND

Figure 5-1. Model 642 Status System (Sheet 1 of 2)

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

5-6 Computer Interface Operation

Name

Used

Not Used

Not

76543210Bit

Used Used

ERST?

Not

Used

Not

Used

Condition Register

Error Status 7

Not

43210Bit

DAC OCFOOV OOCTF

AND

Event Register

Error Status

ERSTR?

Enable Register

Error Status

ERSTE, ERSTE?

ASheet

1 of 2

AND

ERSTE, ERSTE?

Enable Register

Error Status

AND

76543

AND

2 1 0Bit

Name

AND

Event Register

ERST?

Error Status

Condition Register

Error Status

ERSTR?

LLV

67 53

HLVMFF

543

Name

Bit

EPETH CAL

210

Name

Bit

Sheet

B1 of 2

PFFREF

PFFREF HLVMFF LLV EPETH CAL

AND

Hardware Errors

TF = Temperature Fault

DAC = DAC Processor Not Responding

OCF = Output Control Failure

OOV = Output Over Voltage

OOC = Output Over Current

LLV = Low Line Voltage

Operational Errors

EPE = External Current Program Error

TH = Temperature High

HLV = High Line Voltage

MFF = Magnet Flow Switch Fault

PFF = Power Supply Flow Switch Fault

REF = Remote Enable Fault

CAL = Calibration Error

Used

Not

Used

Not

Used

Not

DAC OCFOOV OOC

Figure 5-1. Model 642 Status System (Sheet 2 of 2)

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Computer Interface Operation 5-7

5.1.4.1.6 Reading Registers

Any register in the status system may be read using the appropriate query command. Some registers clear when read,

others do not. Refer to Paragraph 5.1.4.1.7. The response to a query will be a decimal value that corresponds to the

binary-weighted sum of all bits in the register, Refer to Table 5-1. The actual query commands are described later in

this section.

Table 5-1. Binary Weighting of an 8-Bit Register

Position B7 B6 B5 B4 B3 B2 B1 B0

Decimal 128 64 32 16 8 4 2 1

Weighting 27 2

6 2

5 2

4 2

3 2

2 2

1 2

Example: If bits 0, 2, and 4 are set, a query of the register will return a decimal value of 21 (1+4+16).

5.1.4.1.7 Programming Registers

The only registers that may be programmed by the user are the enable registers. All other registers in the status system

are read-only registers. To program an enable register send a decimal value which corresponds to the desired binary-

weighted sum of all bits in the register, Refer to Table 5-1. The actual commands are described later in this section.

5.1.4.1.8 Clearing Registers

The methods to clear each register are detailed in Table 5-2.

Table 5-2. Register Clear Methods

Condition Registers None – registers are not latched —

Query the event register.

*ESR?

(clears Standard Event

Status register)

Send *CLS *CLS

(clears all three registers)

Event Registers:

Standard Event Status Register

Operation Event Register

Error Status Event Register

Power on instrument —

Write 0 to the enable register.

*ESE 0

(clears Standard Event

Status Enable register)

Enable Registers:

Standard Event Status Enable

Operation Event Enable Register

Error Status Enable Register

Service Request Enable Register

Power on instrument —

There are no commands that directly clear

the Status Byte as the bits are non-

latching. To clear individual summary

bits, clear the event register that

corresponds to the summary bit. Sending

*CLS will clear all event registers which

in turn clears the status byte.

If bit 5 (ESB) of the Status

Byte is set, send *ESR? to

read the Standard Event

Status Register and bit 5

will clear.

Status Byte

Power on instrument —

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

5-8 Computer Interface Operation

5.1.4.2 Status Register Sets

As shown in Figure 5-1, there are five register sets in the status system of the Model 642; Standard Event Status

Register, Operation Event Register, Hardware Error Status Register, Operational Error Status Register, and the Persistent

Switch Error Register.

5.1.4.2.1 Standard Event Status Register Set

The Standard Event Status Register reports the following interface related instrument events: power on detected,

command syntax errors, command execution errors, query errors, operation complete. Any or all of these events may be

reported in the standard event summary bit through the enable register, see Figure 5-2. The Standard Event Status Enable

command (*ESE) programs the enable register and the query command (*ESE?) reads it. *ESR? reads and clears the

Standard Event Status Register. The used bits of the Standard Event Register are described as follows:

Power On (PON), Bit (7) – This bit is set to indicate an instrument off-on transition.

Command Error (CME), Bit (5) – This bit is set if a command error has been detected since the last reading. This

means that the instrument could not interpret the command due to a syntax error, an unrecognized header,

unrecognized terminators, or an unsupported command.

Execution Error (EXE), Bit (4) – This bit is set if an execution error has been detected. This occurs when the

instrument is instructed to do something not within its capabilities.

Query Error (QYE), Bit (2) – This bit indicated a query error. It occurs rarely and involves loss of data because the

output queue is full.

Operation Complete (OPC), Bit (0) – When *OPC is sent, this bit will be set when the instrument has completed all

pending operations. The operation of this bit is not related to the *OPC? command which is a separate interface

feature. Refer to Paragraph 5.1.4.4.6 for more information.

Name

Bit

AND

CME

Not

PON

*ESE, *ESE? Used

Standard Event

Status Enable 76

Not OPC

Not

EXE QYE

Used Used

24 3

AND

CME

Standard Event

*ESR?

Status Register

AND

PON Used

Not

QYE

AND

EXE Used

Not Used

Not OPC

OR To bit 5 (ESB) of

Status Byte Register

(See Figure 5-1.)

Figure 5-2. Standard Event Status Register

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Computer Interface Operation 5-9

5.1.4.2.2 Operation Event Register Set

The Operation Event Register reports the following instrument events: ramp done, compliance. Any or all of these events

may be reported in the operation event summary bit through the enable register, see Figure 5-3. The Operation Event

Enable command (OPSTE) programs the enable register and the query command (OPSTE?) reads it. OPSTR? reads the

Operation Event Register. OPST? reads and clears the Operation Condition register. The used bits of the Operation

Event Register are described as follows:

Power Limit, Bit (2) – This bit is set if the output is in power limit.

Ramp Done, Bit (1) – This bit is set when the output current ramp is completed.

Compliance, Bit (0) – This bit is set if the output is in compliance limit.

To Bit 7 (OSB) of

Status Byte Register

(See Figure 5-1.)

AND

Used

Not

NotNotNotNot

OPSTE, Used

OPSTE? UsedUsed Used

Event Enable

Operation

Name

AND

Bit

Used

Not

Used

Not

Used

OPSTR?

Operation

Event 7

NotNot Not

UsedUsed Used

Not

Used

Condition

OPST?

Operation 4

Used

Not

Used

Not Used

Not

3210

Name

Bit

3Bit

Name

Figure 5-3. Operation Event Register

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

5-10 Computer Interface Operation

5.1.4.3 Error Status Register Sets

As shown in Figure 5-1, there are two register sets in the error status system of the Model 642; Hardware Error Status

5.1.4.3.1 Hardware Error Status Register Set

The Hardware Error Status Register reports the following instrument hardware error events: temperature fault, output

over voltage, output over current, DAC processor not responding and output control failure. Any or all of these events

may be reported in the standard event summary bit through the enable register, see Figure 5-4. The Hardware Error

Status Register is the first value of the two values associated with the Error Status Registers. The Error Status Enable

command (ERSTE) programs the enable register and the query command (ERSTE?) reads it. ERSTR? reads and clears

the Error Status Register. The used bits of the Error Status Event Register are described as follows:

Temperature Fault (TF), Bit (4) – This bit is set if the internal temperature of the instrument exceeded the maximum

safe value of 45 °C. The instrument will shut down within 10 seconds of detecting this fault.

Output Over Voltage (OOV), Bit (3) – This bit is set if the output voltage exceeded the compliance voltage limit

setting.

Output Over Current (OOC), Bit (2) – This bit is set if the output current is above 62 A exceeding the maximum

output current of the instrument.

DAC Processor Not Responding (DAC), Bit (1) – This bit is set to indicate that communication to the DAC processor

has failed.

Output Control Failure (OCF), Bit (0) – This bit is set if there is a failure on the output control board.

To Bit 2 (HESB) of

(See Figure 5-1.)

Status Byte Register

NotNot

Event Register Not

Used

Not

UsedUsed

ERSTE, ERSTE?

Error Status

Enable Register Not

Not

ERSTR? Used Used

NameTF

AND

42301Bit

AND

TF Name

Used

Not

Condition Register

Error Status

ERST?

7 6

Not

Used Used

Not

Error Status Bit103 24

OOV

432

DACTF OCF

10Bit

OOC Name

OOV DAC OCFOOC

Figure 5-4. Hardware Error Status Register

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Computer Interface Operation 5-11

5.1.4.3.2 Operational Error Status Register Set

The Operational Error Status Register reports the following instrument operational error events: remote enable fault

detected, power supply flow switch fault detected, magnet flow switch fault detected, high line voltage, low line voltage,

temperature high, external current program error, calibration error. Any or all of these events may be reported in the

standard event summary bit through the enable register, see Figure 5-5. The Operational Error Status Register is the

second value of the two values associated with the Error Status Registers. The Error Status Enable command (ERSTE)

programs the enable register and the query command (ERSTE?) reads it. ERSTR? reads and clears the Error Status

Remote Enable Fault Detected (REF), Bit (7) – This bit is set if a fault condition is detected on the remote enable

interlock.

Power Supply Flow Switch Fault Detected (PFF), Bit (6) – This bit is set if a fault condition is detected on the power

supply flow switch interlock.

Magnet Flow Switch Fault Detected (MFF), Bit (5) – This bit is set if a fault condition is detected on the magnet flow

switch interlock.

High Line Voltage (HLV), Bit (4) – This bit is set if the power line voltage exceeds an acceptable amplitude. Operation

can continue but additional heat may be dissipated by the instrument.

Low Line Voltage (LLV), Bit (3) – This bit is set if the power line voltage drops below an acceptable amplitude.

Operation can continue but output voltage may not reach maximum specification.

Temperature High (OOV), Bit (2) – This bit is set if the internal temperature of the instrument exceeded 40 °C. The

output current will be set to zero and will not be settable until the fault is cleared.

External Current Program Error (EPE), Bit (1) – This bit is set if the instrument cannot go into external or sum

current programming modes because the programming voltage is too high. The output current will be set to zero and

will not be settable until the fault is cleared.

Calibration Error (CAL), Bit (0) – This bit is set if the instrument is not calibrated or the calibration data has been

corrupted.

REF PFF NameCALTH EPEMFF HLV LLV

MFF

Error Status

Enable Register

ERSTE, ERSTE?

REF PFF

ERSTR?

AND

Error Status

ERST?

Event Register 76

AND

EPE

LLVHLV TH

Bit

CAL Name

AND

CALTH EPELLVHLV Name

AND

310Bit

Condition Register

Error Status 76 42

1Bit

Status Byte Register

(See Figure 5-1.)

To Bit 1 (OESB) of

Figure 5-5. Operational Error Status Register

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

5-12 Computer Interface Operation

5.1.4.4 Status Byte and Service Request (SRQ)

As shown in Figure 5-1, the Status Byte Register receives the summary bits from the two status register sets and the

message available summary bit from the output buffer. The status byte is used to generate a service request (SRQ). The

selection of summary bits that will generate an SRQ is controlled by the Service Request Enable Register.

5.1.4.4.1 Status Byte Register

The summary messages from the event registers and output buffer set or clear the summary bits of the Status Byte

summary bit in the Status Byte Register. Reading all messages in the output buffer, including any pending queries, will

clear the message available bit. The bits of the Status Byte Register are described as follows:

Operation Summary (OSB), Bit (7) – Set summary bit indicates that an enabled operation event has occurred.

Request Service (RQS)/Master Summary Status (MSS), Bit (6) – This bit is set when a summary bit and the summary

bits corresponding enable bit in the Service Request Enable Register are set. Once set, the user may read and clear the

bit in two different ways, which is why it is referred to as both the RQS and the MSS bit. When this bit goes from low

to high, the Service Request hardware line on the bus is set, this is the RQS function of the bit. See Paragraph

5.1.4.4.3. In addition, the status of the bit may be read with the *STB? query which returns the binary weighted sum of

all bits in the Status Byte, this is the MSS function of the bit.

Performing a serial poll will automatically clear the RQS function but not the MSS function. A *STB? will read the

status of the MSS bit (along with all of the summary bits), but also will not clear it. To clear the MSS bit, either clear

the event register that set the summary bit or disable the summary bit in the Service Request Enable Register.

Event Summary (ESB), Bit (5) – Set summary bit indicates that an enabled standard event has occurred.

Message Available (MAV), Bit (4) – Set summary bit indicates that a message is available in the output buffer.

Bit (3) – Not used.

Hardware Errors Summary (HESB), Bit (2) – Set summary bit indicates that an enabled hardware error event has

occurred.

Operational Errors Summary (OESB), Bit (1) – Set summary bit indicates that an enabled operational error event has

occurred.

AND

AND OR

MSS

*SRE, *SRE?

Read by *STB?

Enable Register

Service Request

OSB

Not

Used

ESB

Not

Used

MAV

Name

Not

Used

1Bit

RQS AND

Status Byte

request. Reset by

Generate service

serial poll.

*STB?

MSS

RQS ESB Used

Not

MAV

Bit

Name

Used

Not

From Operation Condition Register

From Standard Event Status Register

From Output Buffer

From Error Status Register (Hardware)

From Error Status Register (Operational)

Figure 5-6. Status Byte Register and Service Request Enable Register

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Computer Interface Operation 5-13

5.1.4.4.2 Service Request Enable Register

The Service Request Enable Register is programmed by the user and determines which summary bits of the Status Byte

may set bit 6 (RQS/MSS) to generate a Service Request. Enable bits are logically ANDed with the corresponding

summary bits, see Figure 5-6. Whenever a summary bit is set by an event register and its corresponding enable bit is set

by the user, bit 6 will set to generate a service request. The Service Request Enable command (*SRE) programs the

Service Request Enable Register and the query command (*SRE?) reads it. Reading the Service Request Enable Register

will not clear it. The register may be cleared by the user by sending *SRE 0.

5.1.4.4.3 Using Service Request (SRQ) and Serial Poll

When a Status Byte summary bit (or MAV bit) is enabled by the Service Request Enable Register and goes from 0 to 1,

bit 6 (RQS/MSS) of the status byte will be set. This will send a service request (SRQ) interrupt message to the bus

controller. The user program may then direct the bus controller to serial Poll the instruments on the bus to identify which

one requested service (the one with bit 6 set in its status byte).

Serial polling will automatically clear RQS of the Status Byte Register. This allows subsequent serial polls to monitor bit

6 for an SRQ occurrence generated by other event types. After a serial poll, the same event or any event that uses the

same Status Byte summary bit, will not cause another SRQ unless the event register that caused the first SRQ has been

cleared, typically by a query of the event register.

The serial poll does not clear MSS. The MSS bit stays set until all enabled Status Byte summary bits are cleared,

typically by a query of the associated event register, refer to Paragraph 5.1.4.4.4.

The programming example in Table 5-3 initiates an SRQ when a command error is detected by the instrument.

Table 5-3. Programming Example to Generate an SRQ

Command or Operation Description

*ESR? Read and clear the Standard Event Status Register.

*ESE 32 Enable the Command Error (CME) bit in the Standard Event Status Register

*SRE 32 Enable the Event Summary Bit (ESB) to set the RQS

*ABC Send improper command to instrument to generate a command error

Monitor bus Monitor the bus until the Service Request interrupt (SRQ) is sent.

Initiate Serial Poll Serial Poll the bus to determine which instrument sent the interrupt and clear the RQS bit

in the Status Byte.

*ESR? Read and clear the Standard Event Status Register allowing an SRQ to be generated on

another command error.

5.1.4.4.4 Using Status Byte Query (*STB?)

The Status Byte Query (*STB?) command is similar to a Serial Poll except it is processed like any other instrument

command. The *STB? command returns the same result as a Serial Poll except that the Status Byte bit 6 (RQS/MSS) is

not cleared. In this case bit 6 is considered the MSS bit. Using the *STB? command does not clear any bits in the Status

Byte Register.

5.1.4.4.5 Using Message Available (MAV) Bit

Status Byte summary bit 4 (MAV) indicates that data is available to read into your bus controller. This message may be

used to synchronize information exchange with the bus controller. The bus controller can, for example, send a query

command to the Model 642 and then wait for MAV to set. If the MAV bit has been enabled to initiate an SRQ, the user’s

program can direct the bus controller to look for the SRQ leaving the bus available for other use. The MAV bit will be

clear whenever the output buffer is empty.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

5-14 Computer Interface Operation

5.1.4.4.6 Using Operation Complete (*OPC) and Operation Complete Query (*OPC?)

The Operation Complete (*OPC) and Operation Complete Query (*OPC?) are both used to indicate when pending

device operations complete. However, the commands operate with two distinct methods.

The *OPC command is used in conjunction with bit 0 (OPC) of the Standard Event Status Register. If *OPC is sent as

the last command in a command sequence, bit 0 will be set when the instrument completes the operation that was

initiated by the command sequence. Additional commands may be sent between the instrument and the bus controller

while waiting for the initial pending operation to complete. A typical use of this function would be to enable the OPC bit

to generate an SRQ and include the *OPC command when programming the instrument. The bus controller could then

be instructed to look for an SRQ allowing additional communication with the instrument while the initial process

executes.

The *OPC? query has no interaction with bit 0 (OPC) of the Standard Event Status Register. If the *OPC? query is sent

at the end of a command sequence, the bus will be held until the instrument completes the operation that was initiated by

the command sequence. Additional commands (except *RST) should not be sent until the operation is complete as erratic

operation will occur. Once the sequence is complete a 1 will be placed in the output buffer. This function is typically

used to signal a completed operation without monitoring the SRQ. It is also used when it is important to prevent any

additional communication on the bus during a pending operation.

5.1.5 IEEE-488 Interface Example Programs

A Visual Basic program is included to illustrate the IEEE-488 communication functions of the instrument. Instructions

for setting up the IEEE-488 Board is included in Section 5.1.5.1. Refer to Section 5.1.5.2 for instructions on how to setup

the program. The Visual Basic code is provided in Table 5-5. A description of program operation is provided in

Section 5.1.5.3. While the hardware and software required to produce and implement these programs not included with

the instrument, the concepts illustrated apply to most applications.

5.1.5.1 IEEE-488 Interface Board Installation for Visual Basic Program

This procedure works for Plug and Play GPIB Hardware and Software for Windows 98/95. This example uses the

AT-GPIB/TNT GPIB card.

1. Install the GPIB Plug and Play Software and Hardware using National Instruments instructions.

2. Verify that the following files have been installed to the Windows System folder:

a. gpib-32.dll

b. gpib.dll

c. gpib32ft.dll

Files b and c support any 16-bit Windows GPIB applications being used.

3. Locate the following files and make note of their location. These files will be used during the development process

of a Visual Basic program.

a. Niglobal.bas

b. Vbib-32.bas

NOTE: If the files in Steps 2 and 3 are not installed on your computer, they may be copied from your National

Instruments setup disks or they may be downloaded from www.ni.com.

4. Configure the GPIB by selecting the System icon in the Windows Control Panel located under Settings on the Start

Menu. Configure the GPIB Settings as shown in Figure 5-7. Configure the DEV12 Device Template as shown in

Figure 5-8. Be sure to check the Readdress box.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Computer Interface Operation 5-15

Figure 5-7. GPIB0 Setting Configuration

Figure 5-8. DEV 12 Device Template Configuration

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

5-16 Computer Interface Operation

5.1.5.2 Visual Basic IEEE-488 Interface Program Setup

This IEEE-488 interface program works with Visual Basic 6.0 (VB6) on an IBM PC (or compatible) with a Pentium-

class processor. A Pentium 90 or higher is recommended, running Windows 95 or better. It assumes your IEEE-488

(GPIB) card is installed and operating correctly (refer to Paragraph 5.1.5.1). Use the following procedure to develop the

IEEE-488 Interface Program in Visual Basic.

1. Start VB6.

2. Choose Standard EXE and select Open.

3. Resize form window to desired size.

4. On the Project Menu, select Add Module, select the Existing tab, then navigate to the location on your computer to

add the following files: Niglobal.bas and Vbib-32.bas.

5. Add controls to form:

a. Add three Label controls to the form.

b. Add two TextBox controls to the form.

c. Add one CommandButton control to the form.

6. On the View Menu, select Properties Window.

7. In the Properties window, use the dropdown list to select between the different controls of the current project.

10. Set the properties of the controls as defined in Table 5-4.

11. Save the program.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Computer Interface Operation 5-17

Table 5-4. IEEE-488 Interface Program Control Properties

Current Name Property New Value

Label1 Name

Caption

lblExitProgram

Type “exit” to end program.

Label2 Name

Caption

lblCommand

Command

Label3 Name

Caption

lblResponse

Response

Text1 Name

Text

txtCommand

<blank>

Text2 Name

Text

txtResponse

<blank>

Command1 Name

Caption

Default

cmdSend

Send

True

Form1 Name

Caption

From IEEE-488

IEEE-488 Interface Program

12. Add code (provided in Table 5-5).

a. In the Code Editor window, under the Object dropdown list, select (General). Add the statement: Public gSend

as Boolean

b. Double Click on cmdSend. Add code segment under Private Sub cmdSend_Click( ) as shown in Table 5-5.

c. In the Code Editor window, under the Object dropdown list, select Form. Make sure the Procedure dropdown

list is set at Load. The Code window should have written the segment of code: Private Sub Form_Load( ). Add

the code to this subroutine as shown in Table 5-5.

13. Save the program.

14. Run the program. The program should resemble the following.

15. Type in a command or query in the Command box as described in Paragraph 5.1.5.5.

16. Press Enter or select the Send button with the mouse to send command.

17. Type Exit and press Enter to quit.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

5-18 Computer Interface Operation

Table 5-5. Visual Basic IEEE-488 Interface Program

Public gSend As Boolean 'Global used for Send button state

Private Sub cmdSend_Click() 'Routine to handle Send button press

gSend = True 'Set Flag to True

End Sub

Private Sub Form_Load() 'Main code section

Dim strReturn As String 'Used to return response

Dim term As String 'Terminators

Dim strCommand As String 'Data string sent to instrument

Dim intDevice As Integer 'Device number used with IEEE

frmIEEE.Show 'Show main window

term = Chr(13) & Chr(10) 'Terminators are <CR><LF>

strReturn = "" 'Clear return string

Call ibdev(0, 12, 0, T10s, 1, &H140A, intDevice) 'Initialize the IEEE device

Call ibconfig(intDevice, ibcREADDR,1) 'Setup Repeat Addressing

Do 'Wait loop

DoEvents 'Give up processor to other events

Loop Until gSend = True 'Loop until Send button pressed

gSend = False 'Set Flag as False

strCommand = frmIEEE.txtCommand.Text 'Get Command

strReturn = "" 'Clear response display

strCommand = UCase(strCommand) 'Set all characters to upper case

If strCommand = "EXIT" Then 'Get out on EXIT

End

End If

Call ibwrt(intDevice, strCommand & term) 'Send command to instrument

If (ibsta And EERR) Then 'Check for IEEE errors

'do error handling if needed 'Handle errors here

End If

If InStr(strCommand, "?") <> 0 Then 'Check to see if query

strReturn = Space(100) 'Build empty return buffer

Call ibrd(intDevice, strReturn) 'Read back response

If (ibsta And EERR) Then 'Check for IEEE errors

'do error handling if needed 'Handle errors here

End If

If strReturn <> "" Then 'Check if empty string

strReturn = RTrim(strReturn) 'Remove extra spaces and Terminators

Do While Right(strReturn, 1) = Chr(10) Or Right(strReturn, 1) = Chr(13)

strReturn = Left(strReturn, Len(strReturn) - 1)

Loop

Else

strReturn = "No Response" 'Send No Response

End If

frmIEEE.txtResponse.Text = strReturn 'Put response in text on main form

End If

Loop

End Sub

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Computer Interface Operation 5-19

Primary GPIB Address ........ Primary GPIB Address ........ àà00

Secondary GPIB Address ...... NONESecondary GPIB Address ...... NONE

Timeout setting ............. 10secTimeout setting ............. 10sec

Terminate Read on EOS ....... YesTerminate Read on EOS ....... Yes

Set EOI with EOS on Writes .. YesSet EOI with EOS on Writes .. Yes

Type of compare on EOS ...... 7-BitType of compare on EOS ...... 7-Bit

EOS byte .................... 0AhEOS byte .................... 0Ah

Send EOI at end of Write .... YesSend EOI at end of Write .... Yes

System Controller ........... YesSystem Controller ........... Yes

Assert REN when SC .......... NoAssert REN when SC .......... No

Enable Auto Serial Polling .. NoEnable Auto Serial Polling .. No

Enable CIC Protocol ......... NoEnable CIC Protocol ......... No

Bus Timing .................. 500nsecBus Timing .................. 500nsec

Parallel Poll Duration ...... DefaultParallel Poll Duration ...... Default

Use this GPIB board ......... YesUse this GPIB board ......... Yes

Board Type .................. PCIIBoard Type .................. PCII

Base I/O Address ............ 02B8hBase I/O Address ............ 02B8h

National InstrumentsNational Instruments GPIB0 Configuration GPIB-PC2/2A Ver 2.1

éé Select the primary GPIB address by

using the left and right arrow keys.

This address is used to compute the

talk and listen addresses which

identify the board or device on the

GPIB. Valid primary addresses range

from 0 to 30 (00H to 1EH).

* Adding 32 to the primary address

forms the Listen Address (LA).

* Adding 64 to the primary address

forms the Talk Address (TA).

EXAMPLE: Selecting a primary address

of 10 yields the following:

10 + 32 = 42 (Listen address)

10 + 64 = 74 (Talk address)

F1: Help F6: Reset Value F9/Esc: Return to Map Ctl PgUp/PgDn: Next/Prev Board

Primary GPIB Address ........ àà12

Secondary GPIB Address ...... NONE

Timeout setting ............. 10sec

Serial Poll Timeout ......... 1sec

Terminate Read on EOS ....... Yes

Set EOI with EOS on Writes .. Yes

Type of compare on EOS ...... 7-Bit

EOS byte .................... 0Ah

Send EOI at end of Write .... Yes

Enable Repeat Addressing .... Yes

National Instruments DEV12 Configuration GPIB-PC2/2A Ver 2.1

Select the primary GPIB address by

using the left and right arrow keys.

This address is used to compute the

talk and listen addresses which

identify the board or device on the

GPIB. Valid primary addresses range

from 0 to 30 (00H to 1EH).

* Adding 32 to the primary address

forms the Listen Address (LA).

* Adding 64 to the primary address

forms the Talk Address (TA).

EXAMPLE: Selecting a primary address

of 10 yields the following:

10 + 32 = 42 (Listen address)

10 + 64 = 74 (Talk address)

F1: Help F6: Reset Value F9/Esc: Return to Map Ctl PgUp/PgDn: Next/Prev Board

êê

éé

IBCONF.EXE.eps

Figure 5-9. Typical National Instruments GPIB Configuration from IBCONF.EXE

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

5-20 Computer Interface Operation

5.1.5.3 Program Operation

Once the running, try the following commands and observe the response of the instrument. Input from the user is shown

in bold and terminators are added by the program. The word [term] indicates the required terminators included with the

response.

ENTER COMMAND? *IDN? Identification query. Instrument will return a string identifying itself.

RESPONSE: LSCI,MODELModel 642,1234567,06122006[term]

ENTER COMMAND? SETI? Output current setting query. Instrument will return a string with the

present output current setting.

RESPONSE: +20.0545[term]

ENTER COMMAND? XPGM 0 External program mode command. Instrument will set program mode

to internal. No response will be sent.

ENTER COMMAND? XPGM? External program mode query. Instrument will return a string with the

present external program mode setting.

RESPONSE: 0[term]

ENTER COMMAND? XPGM 1;XPGM? External program mode command followed by a query. Instrument will

change to external programming mode, then return a string

RESPONSE: 1[term] with the present setting.

The following are additional notes on using either IEEE-488 Interface program.

• If you enter a correctly spelled query without a “?,” nothing will be returned. Incorrectly spelled commands and

queries are ignored. Commands and queries should have a space separating the command and associated parameters.

• Leading zeros and zeros following a decimal point are not needed in a command string, but are sent in response to a

query. A leading “+” is not required but a leading “–” is required.

5.1.6 Troubleshooting

New Installation

1. Check instrument address.

2. Always send terminators.

3. Send entire message string at one time including terminators.

4. Send only one simple command at a time until communication is established.

5. Be sure to spell commands correctly and use proper syntax.

6. Attempt both ‘Talk’ and ‘Listen’ functions. If one works but not the other, the hardware connection is working, so

look at syntax, terminators, and command format.

7. If only one message is received after resetting the interface, check the “repeat addressing” setting. It should be

enabled.

Old Installation No Longer Working

8. Power instrument off then on again to see if it is a soft failure.

9. Power computer off then on again to see if the IEEE-488 card is locked up.

10. Verify that the address has not been changed on the instrument during a memory reset.

11. Check all cable connections.

Intermittent Lockups

12. Check cable connections and length.

13. Increase delay between all commands to 50 ms to make sure instrument is not being over loaded.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Computer Interface Operation 5-21

5.2 SERIAL INTERFACE OVERVIEW

The serial interface used in the Model 642 is commonly referred to as an RS-232C interface. RS-232C is a standard of

the Electronics Industries Association (EIA) that describes one of the most common interfaces between computers and

electronic equipment. The RS-232C standard is quite flexible and allows many different configurations. However, any

two devices claiming RS-232C compatibility cannot necessarily be plugged together without interface setup. The

remainder of this paragraph briefly describes the key features of a serial interface that are supported by the instrument.

A customer supplied computer with similarly configured interface port is required to enable communication.

5.2.1 Changing Baud Rate

To select the Serial Interface Baud Rate press the Computer Interface key. The first computer interface screen appears

as a prompt for Baud.

Computer Interface

Select With °®

Baud: 9600

Use the S or T key to select 9600, 19200, 38400, or 57600 Baud. The default is 9600 Baud. Press Enter to accept the

new selection and continue to the next setting screen. Press Escape to cancel the new selection and return to the normal

display.

5.2.2 Physical Connection

The Model 642 has a 9 pin D-Subminiature plug on the rear panel for serial communication. The original RS-232C

standard specifies 25 pins but both 9- and 25-pin connectors are commonly used in the computer industry. Many third

party cables exist for connecting the instrument to computers with either 9- or 25-pin connectors. Paragraph 7.10.5 gives

the most common pin assignments for 9- and 25-pin connectors. Please note that not all pins or functions are supported

by the Model 642.

The instrument serial connector is the plug half of a mating pair and must be matched with a socket on the cable. If a

cable has the correct wiring configuration but also has a plug end, a “gender changer” can be used to mate two plug ends

together.

The letters DTE near the interface connector stand for Data Terminal Equipment and indicate the pin connection of the

directional pins such as transmit data (TD) and receive data (RD). Equipment with Data Communications Equipment

(DCE) wiring can be connected to the instrument with a straight through cable. As an example, Pin 3 of the DTE

connector holds the transmit line and Pin 3 of the DCE connector holds the receive line so the functions complement.

It is likely both pieces of equipment are wired in the DTE configuration. In this case Pin 3 on one DTE connector (used

for transmit) must be wired to Pin 2 on the other (used for receive). Cables that swap the complementing lines are called

null modem cables and must be used between two DTE wired devices. Null modem adapters are also available for use

with straight through cables. Paragraph 7.10.5 illustrates suggested cables that can be used between the instrument and

common computers.

The instrument uses drivers to generate the transmission voltage levels required by the RS-232C standard. These

voltages are considered safe under normal operating conditions because of their relatively low voltage and current limits.

The drivers are designed to work with cables up to 50 feet in length.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

5-22 Computer Interface Operation

5.2.3 Hardware Support

The Model 642 interface hardware supports the following features. Asynchronous timing is used for the individual bit

data within a character. This timing requires start and stop bits as part of each character so the transmitter and receiver

can be resynchronized between each character. Half duplex transmission allows the instrument to be either a transmitter

or a receiver of data but not at the same time. Communication speeds of 9600, 19200, 38400, or 57600 Baud are

supported. The Baud rate is the only interface parameter that can be changed by the user.

Hardware handshaking is not supported by the instrument. Handshaking is often used to guarantee that data message

strings do not collide and that no data is transmitted before the receiver is ready. In this instrument appropriate software

timing substitutes for hardware handshaking. User programs must take full responsibility for flow control and timing as

described in Paragraph 5.2.6.

5.2.4 Character Format

A character is the smallest piece of information that can be transmitted by the interface. Each character is 10 bits long

and contains data bits, bits for character timing and an error detection bit. The instrument uses 7 bits for data in the

ASCII format. One start bit and one stop bit are necessary to synchronize consecutive characters. Parity is a method of

error detection. One parity bit configured for odd parity is included in each character.

ASCII letter and number characters are used most often as character data. Punctuation characters are used as delimiters

to separate different commands or pieces of data. Two special ASCII characters, carriage return (CR 0DH) and line feed

(LF 0AH), are used to indicate the end of a message string.

Table 5-6. Serial Interface Specifications

Connector Type:

Connector Wiring:

Voltage Levels:

Transmission Distance:

Timing Format:

Transmission Mode:

Baud Rate:

Handshake:

Character Bits:

Parity:

Terminators:

Command Rate:

9-pin D-style connector plug

DTE

EIA RS-232C Specified

50 feet maximum

Asynchronous

Half Duplex

9600, 19200, 38400, 57600

Software timing

1 Start, 7 Data, 1 Parity, 1 Stop

Odd

CR(0DH) LF(0AH)

20 commands per second maximum

5.2.5 Message Strings

A message string is a group of characters assembled to perform an interface function. There are three types of message

strings commands, queries and responses. The computer issues command and query strings through user programs, the

instrument issues responses. Two or more command or query strings can be chained together in one communication but

they must be separated by a semi-colon (;). The total communication string must not exceed 255 characters in length.

A command string is issued by the computer and instructs the instrument to perform a function or change a parameter

setting. The format is:

<command mnemonic><space><parameter data><terminators>.

Command mnemonics and parameter data necessary for each one is described in Paragraph 5.3. Terminators must be

sent with every message string.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Computer Interface Operation 5-23

Message Strings (Continued)

A query string is issued by the computer and instructs the instrument to send a response. The query format is:

<query mnemonic><?><space><parameter data><terminators>.

Query mnemonics are often the same as commands with the addition of a question mark. Parameter data is often

unnecessary when sending queries. Query mnemonics and parameter data if necessary is described in Paragraph 5.3.

Terminators must be sent with every message string. The computer should expect a response very soon after a query

is sent.

A response string is the instruments response or answer to a query string. The instrument will respond to the last query

or queries it receives. The response can be a reading value, status report or the present value of a parameter. Response

data formats are listed along with the associated queries in Paragraph 5.3. The response is sent as soon as possible after

the instrument receives the query. Typically it takes 10 ms for the instrument to begin the response. Some responses

take longer.

5.2.6 Message Flow Control

It is important to remember that the user program is in charge of the serial communication at all times. The instrument

cannot initiate communication, determine which device should be transmitting at a given time or guarantee timing

between messages. All of this is the responsibility of the user program.

When issuing commands only the user program should:

• Properly format and transmit the command including terminators as one string.

• Guarantee that no other communication is started for 50 ms after the last character is transmitted.

• Not initiate communication more than 20 times per second.

When issuing queries or queries and commands together the user program should:

• Properly format and transmit the query including terminators as one string.

• Prepare to receive a response immediately.

• Receive the entire response from the instrument including the terminators.

• Guarantee that no other communication is started during the response or for 50 ms after it completes.

• Not initiate communication more than 20 times per second.

Failure to follow these simple rules will result in inability to establish communication with the instrument or intermittent

failures in communication.

5.2.7 Serial Interface Example Programs

A Visual BASIC program is included to illustrate the serial communication functions of the instrument. Refer to

Paragraph 5.2.7.1 for instructions on how to setup the program. The Visual Basic code is provided in Table 5-8. Refer to

Paragraph 5.2.7.2 for instructions on how to setup the program. A description of operation is provided in Paragraph

5.2.7.2. While the hardware and software required to produce and implement these programs not included with the

instrument, the concepts illustrated apply to almost any application where these tools are available.

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5-24 Computer Interface Operation

5.2.7.1 Visual Basic Serial Interface Program Setup

The serial interface program works with Visual Basic 6.0 (VB6) on an IBM PC (or compatible) with a Pentium-class

processor. A Pentium 90 or higher is recommended, running Windows 95 or better, with a serial interface. It uses the

COM1 communications port at 9600 Baud. Use the following procedure to develop the Serial Interface Program in

Visual Basic.

1. Start VB6.

2. Choose Standard EXE and select Open.

3. Resize form window to desired size.

4. On the Project Menu, click Components to bring up a list of additional controls available in VB6.

5. Scroll through the controls and select Microsoft Comm Control 6.0. Select OK. In the toolbar at the left of the

screen, the Comm Control will have appeared as a telephone icon.

6. Select the Comm control and add it to the form.

7. Add controls to form:

a. Add three Label controls to the form.

b. Add two TextBox controls to the form.

c. Add one CommandButton control to the form.

d. Add one Timer control to the form.

8. On the View Menu, select Properties Window.

9. In the Properties window, use the dropdown list to select between the different controls of the current project.

10. Set the properties of the controls as defined in Table 5-7.

11. Save the program.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Computer Interface Operation 5-25

Table 5-7 Serial Interface Program Control Properties

Current Name Property New Value

Label1 Name

Caption

lblExitProgram

Type “exit” to end program.

Label2 Name

Caption

lblCommand

Command

Label3 Name

Caption

lblResponse

Response

Text1 Name

Text

txtCommand

<blank>

Text2 Name

Text

txtResponse

<blank>

Command1 Name

Caption

Default

cmdSend

Send

True

Form1 Name

Caption

frmSerial

Serial Interface Program

Timer1 Enabled

Interval

False

12. Add code (provided in Table 5-8).

a. In the Code Editor window, under the Object dropdown list, select (General). Add the statement: Public gSend

as Boolean

b. Double Click on cmdSend. Add code segment under Private Sub cmdSend_Click( ) as shown in Table 5-8.

c. In the Code Editor window, under the Object dropdown list, select Form. Make sure the Procedure dropdown

list is set at Load. The Code window should have written the segment of code: Private Sub Form_Load( ).

Add the code to this subroutine as shown in Table 5-8.

d. Double Click on the Timer control. Add code segment under Private Sub Timer1_Timer() as shown in

Table 5-8.

e. Make adjustments to code if different Com port settings are being used.

13. Save the program.

14. Run the program. The program should resemble the following.

15. Type in a command or query in the Command box as described in Paragraph 5.2.7.2.

16. Press Enter or select the Send button with the mouse to send command.

17. Type Exit and press Enter to quit.

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5-26 Computer Interface Operation

Table 5-8. Visual Basic Serial Interface Program

Public gSend As Boolean 'Global used for Send button state

Private Sub cmdSend_Click() 'Routine to handle Send button press

gSend = True 'Set Flag to True

End Sub

Private Sub Form_Load() 'Main code section

Dim strReturn As String 'Used to return response

Dim strHold As String 'Temporary character space

Dim Term As String 'Terminators

Dim ZeroCount As Integer 'Counter used for Timing out

Dim strCommand As String 'Data string sent to instrument

frmSerial.Show 'Show main window

Term = Chr(13) & Chr(10) 'Terminators are <CR><LF>

ZeroCount = 0 'Initialize counter

strReturn = "" 'Clear return string

strHold = "" 'Clear holding string

If frmSerial.MSComm1.PortOpen = True Then 'Close serial port to change settings

frmSerial.MSComm1.PortOpen = False

End If

frmSerial.MSComm1.CommPort = 1 'Example of Comm 1

frmSerial.MSComm1.Settings = "9600,o,7,1" 'Example of 9600 Baud,Parity,Data,Stop

frmSerial.MSComm1.InputLen = 1 'Read one character at a time

frmSerial.MSComm1.PortOpen = True 'Open port

Do 'Wait loop

DoEvents 'Give up processor to other events

Loop Until gSend = True 'Loop until Send button pressed

gSend = False 'Set Flag as false

strCommand = frmSerial.txtCommand.Text 'Get Command

strReturn = "" 'Clear response display

strCommand = UCase(strCommand) 'Set all characters to upper case

If strCommand = "EXIT" Then 'Get out on EXIT

End

End If

frmSerial.MSComm1.Output = strCommand & Term 'Send command to instrument

If InStr(strCommand, "?") <> 0 Then 'Check to see if query

While (ZeroCount < 20) And (strHold <> Chr$(10)) 'Wait for response

If frmSerial.MSComm1.InBufferCount = 0 Then 'Add 1 to timeout if no character

frmSerial.Timer1.Enabled = True

DoEvents 'Wait for 10 millisecond timer

Loop Until frmSerial.Timer1.Enabled = False

ZeroCount = ZeroCount + 1 'Timeout at 2 seconds

Else

ZeroCount = 0 'Reset timeout for each character

strHold = frmSerial.MSComm1.Input 'Read in one character

strReturn = strReturn + strHold 'Add next character to string

End If

Wend 'Get characters until terminators

If strReturn <> "" Then 'Check if string empty

strReturn = Mid(strReturn, 1, InStr(strReturn, Term) – 1) 'Strip terminators

Else

strReturn = "No Response" 'Send No Response

End If

frmSerial.txtResponse.Text = strReturn 'Put response in textbox on main form

strHold = "" 'Reset holding string

ZeroCount = 0 'Reset timeout counter

End If

Loop

End Sub

Private Sub Timer1_Timer() 'Routine to handle Timer interrupt

frmSerial.Timer1.Enabled = False 'Turn off timer

End Sub

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Computer Interface Operation 5-27

5.2.7.2 Program Operation

Once the example program is running, try the following commands and observe the response of the instrument. Input

from the user is shown in bold and terminators are added by the program. The word [term] indicates the required

terminators included with the response.

ENTER COMMAND? *IDN? Identification query. Instrument will return a string identifying itself.

RESPONSE: LSCI,MODELModel 642,1234567,06122006[term]

ENTER COMMAND? SETI? Output current setting query. Instrument will return a string with the

present output current setting.

RESPONSE: +20.0545[term]

ENTER COMMAND? XPGM 0 External program mode command. Instrument will set program mode

to internal. No response will be sent.

ENTER COMMAND? XPGM? External program mode query. Instrument will return a string with the

present external program mode setting.

RESPONSE: 0[term]

ENTER COMMAND? XPGM 1;XPGM? External program mode command followed by a query. Instrument will

change to external programming mode, then return a string

RESPONSE: 1[term] with the present setting.

The following are additional notes on using either IEEE-488 Interface program.

• If you enter a correctly spelled query without a “?,” nothing will be returned. Incorrectly spelled commands and

queries are ignored. Commands and queries should have a space separating the command and associated parameters.

• Leading zeros and zeros following a decimal point are not needed in a command string, but are sent in response to a

query. A leading “+” is not required but a leading “–” is required.

5.2.8 Troubleshooting

New Installation

1. Check instrument Baud rate.

2. Make sure transmit (TD) signal line from the instrument is routed to receive (RD) on the computer and vice versa.

(Use a null modem adapter if not).

3. Always send terminators.

4. Send entire message string at one time including terminators. (Many terminal emulation programs do not.)

5. Send only one simple command at a time until communication is established.

6. Be sure to spell commands correctly and use proper syntax.

Old Installation No Longer Working

7. Power instrument off then on again to see if it is a soft failure.

8. Power computer off then on again to see if communication port is locked up.

9. Verify that Baud rate has not been changed on the instrument during a memory reset.

10. Check all cable connections.

Intermittent Lockups

11. Check cable connections and length.

12. Increase delay between all commands to 100 ms to make sure instrument is not being over loaded.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

5-28 Computer Interface Operation

5.3 COMMAND SUMMARY

This paragraph provides a listing of the IEEE-488 and Serial Interface Commands. A summary of all the commands is

provided in Table 5-9. All the commands are detailed in Paragraph 5.3.1, which is presented in alphabetical order.

Sample Command Format

SETI Output Current Setting Command

Input: SETI <current> [term]

Format: ±nn.nnnn

<current> Specifies the output current setting: 0.0000 – ±70.1000A.

Remarks: Sets the current value that the output will ramp to at the present ramp rate.

Setting value is limited by LIMIT.

Sample Query Format

SETI? Output Current Setting Query

Input: SETI? [term]

Returned: <current> [term]

Format: ±nn.nnnn (Refer to command for description)

Key

Q Begins common interface command.

? Required to identify queries.

aa… String of alpha numeric characters.

±nn… String of number characters that may include a decimal point.

[term] Terminator characters.

<…> Indicated a parameter field, many are command specific.

<state> Parameter field with only On/Off states.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Computer Interface Operation 5-29

Table 5-9. Command Summary

Command Function Page Command Function ......................................................Page

*CLS Clear Interface Cmd ..................................29 INTWR? Internal Water Mode Query ........................33

*ESE Event Status Enable Cmd..........................29 KEYST? Keypad Status Query ..................................33

*ESE? Event Status Enable Query........................30 LIMIT Limit Output Settings Cmd.........................34

*ESR? Event Status Register Query ..................... 30 LIMIT? Limit Output Settings Query.......................33

*IDN? Identification Query .................................. 30 LOCK Keypad Lock Cmd ......................................34

*OPC Operation Complete Cmd .........................30 LOCK? Keypad Lock Query....................................34

*OPC? Operation Complete Query .......................30 MAGWTR Magnet Water Mode Command..................34

*RST Reset Instrument Cmd...............................30 MAGWTR? Magnet Water Mode Query ........................34

*SRE Service Request Enable Cmd ....................31 MODE IEEE Interface Mode Cmd..........................34

*SRE? Service Request Enable Query..................31 MODE? IEEE Interface Mode Query .......................34

*STB? Status Byte Query .....................................31 OPST? Operational Status Query............................35

*TST? Self-Test Query.........................................31 OPSTE Operational Status Enable Cmd ..................35

*WAI Wait-To-Continue Cmd ............................31 OPSTE? Operational Status Enable Query................35

BAUD RS-232C Baud Rate Cmd .........................31 OPSTR? Operational Status Register Query..............35

BAUD? RS-232C Baud Rate Query .......................31 RATE Current Ramp Rate Setting Cmd ................35

DFLT Factory Defaults Cmd ...............................32 RATE? Current Ramp Rate Setting Query ..............35

DISP Display Parameter Cmd ............................32 RDGI? Current Output Reading Query...................35

DISP? Display Parameter Query ..........................32 RDGV? Output Voltage Reading Query...................36

ERCL Error Clear Cmd........................................32 RSEG Ramp Segments Enable Cmd......................36

ERST? Error Status Query ....................................32 RSEG? Ramp Segments Enable Query ...................36

ERSTE Error Status Enable Cmd...........................32 RSEGS Ramp Segments Parameters Cmd ...............36

ERSTE? Error Status Enable Query ........................ 32 RSEGS? Ramp Segments Parameters Query.............36

ERSTR? Error Status Register Query ......................33 SETI Output Current Setting Cmd .......................36

IEEE IEEE-488 Interface Parameter Cmd..........33 SETI? Output Current Setting Query .....................36

IEEE? IEEE-488 Interface Parameter Query........33 STOP Stop Output Current Ramp Cmd.................37

INTWR Internal Water Mode Command ..............33 XPGM External Program Mode Cmd .....................37

XPGM? External Program Mode Query ...................37

5.3.1 Interface Commands (Alphabetical Listing)

*CLS Clear Interface Command

Input: *CLS[term]

Remarks: Clears the bits in the Status Byte Register and Standard Event Status Register and terminates all

pending operations. Clears the interface, but not the instrument. The related instrument command

is *RST.

*ESE Standard Event Status Enable Register Command

Input: *ESE <bit weighting>[term]

Format: nnn

Remarks: The Standard Event Status Enable Register determines which bits in the Standard Event Status

a decimal value that corresponds to the binary-weighted sum of all bits in the register. Refer to

Paragraph 5.1.4.2.1.

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5-30 Computer Interface Operation

*ESE? Standard Event Status Enable Register Query

Input: *ESE?[term]

Returned: <bit weighting>[term]

Format: nnn (Refer to command for description)

*ESR? Standard Event Status Register Query

Input: *ESR?[term]

Returned: <bit weighting>

Format: nnn

Remarks: Bits in this register correspond to various system events and latch when the event occurs. When an

event bit is set, subsequent events corresponding to that bit are ignored. Set bits remain latched until

the register is reset by this query or a *CLS command. Refer to Paragraph 5.1.4.2.1.

*IDN? Identification Query

Input: *IDN?[term]

Returned: <manufacturer>,<model>,<serial>,<firmware version>[term]

Format: aaaa,aaaaaaaa,aaaaaaa,n.n/n.n

<manufacture> Manufacturer ID

<model> Instrument model number

<serial> Serial number

<firmware version> Instrument firmware version, main firmware/DAC firmware.

Example: LSCI,MODEL642,1234567,1.0/1.0

*OPC Operation Complete Command

Input: *OPC[term]

Remarks: Used in conjunction with bit 0 (OPC of the Standard Event Status Register. If sent as the last command

in a command sequence, bit 0 will be set when the instrument completes the operation that was

initiated by the command sequence. Refer to Paragraph 5.1.4.4.6 for more information.

*OPC? Operation Complete Query

Input: *OPC?[term]

Returned: 1[term]

Remarks: Has no interaction with bit 0 (OPC) of the Standard Event Status Register. If sent at the end of a

command sequence, the bus will be held until the instrument completes the operation that was initiated

by the command sequence. Once the sequence is complete a 1 will be placed in the output buffer.

Refer to Paragraph 5.1.4.4.6 for more information.

*RST Reset Instrument Command

Input: *RST[term]

Remarks: Sets controller parameters to power-up settings. Use the DFLT command to set factory defaults.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Computer Interface Operation 5-31

*SRE Service Request Enable Register Command

Input: *SRE <bit weighting>[term]

Format: nnn

Remarks: The Service Request Enable Register determines which summary bits of the Status Byte may set bit 6

(RQS/MSS) of the Status Byte to generate a Service Request. This command programs the enable

Refer to Paragraph 5.1.4.4.

*SRE? Service Request Enable Register Query

Input: *SRE?[term]

Returned: <bit weighting>[term]

Format: nnn (Refer to command for description)

*STB? Status Byte Query

Input: *STB?[term]

Returned: <bit weighting>[term]

Format: nnn

Remarks: This command is similar to a Serial Poll except it is processed like any other instrument command. It

returns the same result as a Serial Poll except that the Status Byte bit 6 (RQS/MSS) is not cleared.

Refer to paragraph 5.1.4.4.4

*TST? Self-Test Query

Input: *TST?[term]

Returned: <status>[term]

Format: n

<status> 0 = No errors found, 1 = Errors found

Remarks: The Model 642 reports status based on test done at power up.

*WAI Wait-to-Continue Command

Input: *WAI[term]

Remarks: This command is not supported in the Model 642.

BAUD RS-232C Baud Rate Command

Input: BAUD <bps>[term]

Format: n

<bps> Specifies Baud rate: 0 = 9600 Baud, 1 = 19200 Baud, 2 = 38400 Baud, 3 = 57600 Baud.

BAUD? RS-232C Baud Rate Query

Input: BAUD?[term]

Returned: <bps>[term]

Format: n (Refer to command for description)

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5-32 Computer Interface Operation

DFLT Factory Defaults Command

Input: DFLT 99[term]

Remarks: Sets all configuration values to factory defaults and resets the instrument. The instrument must be at

zero amps for this command to work. The "99" is included to prevent accidentally setting the unit to

defaults.

DISP Display Parameter Command

Input: DISP <brightness> [term]

Format: n

<brightness> Specifies display brightness: 0 = 25%, 1 = 50%, 2 = 75%, 3 = 100%.

DISP? Display Parameter Query

Input: DISP? [term]

Returned: <brightness> [term]

Format: n (Refer to command for definition).

ERCL Error Clear Command

Input: ERCL [term]

Remarks: This command will clear the operational errors. The errors will only be cleared if the error conditions

have been removed. Hardware errors can never be cleared. Refer to Paragraph 5.1.4.3 for a list of error

bits.

ERST? Error Status Query

Input: ERST? [term]

Returned: <hardware errors>, <operational errors> [term]

Format: nnn,nnn

Remarks: The integers returned represent the sum of the bit weighting of the error bits. Refer to

Paragraph 5.1.4.3 for a list of error bits. Use the ERRCL command to clear the operational errors.

Hardware errors cannot be cleared.

ERSTE Error Status Enable Command

Input: ERSTE <hardware errors>, <operational errors> [term]

Format: nnn,nnn

Remarks: Each bit has a bit weighting and represents the enable/disable mask of the corresponding error bits in

the Error Status Register. This determines which status bits can set the corresponding summary bits in

the Status Byte Register. To enable an error bit, send the command ERSTE with the sum of the bit

weighting for each desired bit. Refer to Paragraph 5.1.4.3 for a list of error bits.

ERSTE? Error Status Enable Query

Input: ERSTE?[term]

Returned: <hardware errors>, <operational errors> [term]

Format: nnn,nnn Refer to Paragraph 5.1.4.3 for a list of error bits.

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Computer Interface Operation 5-33

ERSTR? Error Status Register Query

Input: ERSTR? [term]

Returned: <hardware errors>, <operational errors> [term]

Format: nnn,nnn

Remarks: The integers returned represent the sum of the bit weighting of the error bits. These error bits are

latched when an error condition is detected. This register is cleared when it is read. Refer to

Paragraph 5.1.4.3 for a list of error bits. Use the ERRCL command to clear the operational errors.

Hardware errors cannot be cleared.

IEEE IEEE-488 Interface Parameter Command

Input: IEEE <terminator>, <EOI enable>, <address>[term]

Format: n,n,nn

<terminator> Specifies the terminator. Valid entries: 0 = <CR><LF>,1 = <LF><CR>,

2 = <LF>, 3 = No terminator (must have EOI enabled).

<EOI enable> Sets EOI mode: 0 = Enabled, 1 = Disabled.

<address> Specifies the IEEE address: 1 – 30. (Address 0 and 31 are reserved.)

Example: IEEE 0,0,4[term] – After receipt of the current terminator, the instrument uses <CR><LF> as the

new terminator, uses EOI mode, and responds to address 4.

IEEE? IEEE-488 Interface Parameter Query

Input: IEEE?[term]

Returned: <terminator>, <EOI enable>, <address>[term]

Format: n,n,nn (Refer to command for description)

<mode> 0 = Manual Off, 1 = Manual On, 2 = Auto, 3 = Disabled

INTWTR Internal Water Mode Command

Input: INTWTR <mode> [term]

Format: n

<mode> 0 = Manual Off, 1 = Manual On, 2 = Auto, 3 = Disabled

Example: INTWTR 2[term] – Places the internal water mode to Auto, which will automatically control the

power supply water valve based on the internal power dissipation and temperature.

INTWTR? Internal Water Mode Query

Input: INTWTR? [term]

Returned: <mode>[term]

Format: n (Refer to command for description)

KEYST? Keypad Status Query

Input: KEYST?[term]

Returned: <code>[term]

Format: nn

Remarks: Returns a number descriptor of the last key pressed since the last KEYST?.

Returns “01” after initial power-up. Returns “00” if no key pressed since last query.

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5-34 Computer Interface Operation

LIMIT Limit Output Settings Command

Input: LIMIT <current>, <rate> [term]

Format: +nn.nnnn, +nn.nnnn

<current> Specifies the maximum output current setting allowed: 0 – 70.1000 A.

<rate> Specifies the maximum output current ramp rate setting allowed: 0.0001 – 99.999 A/s.

Remarks: Sets the upper setting limits for output current, compliance voltage, and output current ramp rate. This

is a software limit that will limit the settings to these maximum values.

LIMIT? Limit Output Settings Query

Input: LIMIT? [term]

Returned: <current>, <rate> [term]

Format: +nn.nnnn, +nn.nnnn (Refer to command for description)

LOCK Keypad Lock Command

Input: LOCK <state>, <code>[term]

Format: n,nnn

<state> 0 = Unlock, 1 = Lock All, 2 = Lock Limits.

<code> Specifies lock-out code. Valid entries are 000 – 999.

Remarks: Locks out all front panel entries operations.

Example: LOCK 1,123[term] – Enables keypad lock and sets the code to 123.

LOCK? Keypad Lock Query

Input: LOCK?[term]

Returned: <state>, <code>[term]

Format: n,nnn (Refer to command for description)

MAGWTR Magnet Water Mode Command

Input: MAGWTR <mode>[term]

Format: n

<mode> 0 = Manual Off, 1 = Manual On, 2 = Auto, 3 = Disabled.

Example: MAGWTR 2[term] – Places the magnet water mode to Auto, which will automatically control the

magnet water valve based on the calculated output power.

MAGWTR? Magnet Water Mode Query

Input: MAGWTR?[term]

Returned: <mode>[term]

Format: n (Refer to command for description)

MODE IEEE Interface Mode Command

Input: MODE <mode>[term]

Format: n

<mode> 0 = Local, 1 = Remote, 2 = Remote with local lockout.

Example: MODE 2[term] – Places the Model 642 into remote mode with local lockout.

MODE? IEEE Interface Mode Query

Input: MODE?[term]

Returned: <mode>[term]

Format: n (Refer to command for description)

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Computer Interface Operation 5-35

OPST? Operational Status Query

Input: OPST? [term]

Returned: <bit weighting> [term]

Format: nnn

Remarks: The integer returned represents the sum of the bit weighting of the operational status bits. Refer to

Paragraph 5.1.4.2.2 for a list of operational status bits.

OPSTE Operational Status Enable Command

Input: OPSTE <bit weighting> [term]

Format: nnn

Remarks: Each bit has a bit weighting and represents the enable/disable mask of the corresponding operational

status bit in the Operational Status Register. This determines which status bits can set the

corresponding summary bit in the Status Byte Register. To enable a status bit, send the command

OPSTE with the sum of the bit weighting for each desired bit. Refer to Paragraph 5.1.4.2.2 for a list

of operational status bits.

OPSTE? Operational Status Enable Query

Input: OPSTE?[term]

Returned: <bit weighting> [term]

Format: nnn Refer to Paragraph 5.1.4.2.2 for a list of operational status bits.

OPSTR? Operational Status Register Query

Input: OPSTR? [term]

Returned: <bit weighting> [term]

Format: nnn

Remarks: The integers returned represent the sum of the bit weighting of the operational status bits. These status

bits are latched when the condition is detected. This register is cleared when it is read. Refer to

Paragraph 5.1.4.2.2 for a list of operational status bits.

RATE Output Current Ramp Rate Setting Command

Input: RATE <rate> [term]

Format: +n.nnnn

<rate> Specifies the rate at which the current will ramp at when a new output current setting is

entered: 0.0001 – 99.999 A/s.

Remarks: Sets the output current ramp rate. This value will be used in both the positive and negative directions.

Setting value is limited by LIMIT.

RATE? Output Current Ramp Rate Setting Query

Input: RATE? [term]

Returned: <rate> [term]

Format: +n.nnnn (Refer to command for description)

RDGI? Current Output Reading Query

Input: RDGI? [term]

Returned: <current> [term]

Format: ±nn.nnnn

<current> Actual measured output current.

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5-36 Computer Interface Operation

RDGV? Output Voltage Reading Query

Input: RDGV? [term]

Returned: <voltage> [term]

Format: ±n.nnnn

<voltage> Actual output voltage measured at the power supply terminals.

RSEG Ramp Segments Enable Command

Input: RSEG <enable> [term]

Format: n [term]

<enable> Specifies if ramp segments are to be used: 0 = Disabled, 1 = Enabled.

Remarks: Ramp segments are used to change the output current ramp rate based on the output current. Ramp

segments need to be setup first using the RSEGS command.

RSEG? Ramp Segments Enable Query

Input: RSEG? [term]

Returned: <enable> [term]

Format: n (Refer to command for description)

RSEGS Ramp Segments Parameters Command

Input: RSEGS <segment>, <current>, <rate> [term]

Format: n, +nn.nnnn, +n.nnnn [term]

<segment> Specifies the ramp segment to be modified: 1 – 5.

<current> Specifies the upper output current setting that will use this segment:

0.0000 – +70.1000A.

<rate> Specifies the rate at which the current will ramp at when the output current is in this

segment: 0.0001 – 99.999 A/s.

Remarks: Ramp segments are used to change the output current ramp rate based on the output current. The ramp

segment feature needs to be turned on using the RSEG command.

RSEGS? Ramp Segments Parameters Query

Input: RSEGS? <segment>[term]

Returned: <current>, <rate> [term]

Format: +nn.nnnn, +n.nnnn (Refer to command for description)

SETI Output Current Setting Command

Input: SETI <current> [term]

Format: ±nn.nnnn

<current> Specifies the output current setting: 0.0000 – ±70.1000A.

Remarks: Sets the current value that the output will ramp to at the present ramp rate.

Setting value is limited by LIMIT.

SETI? Output Current Setting Query

Input: SETI? [term]

Returned: <current> [term]

Format: ±nn.nnnn (Refer to command for description)

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Computer Interface Operation 5-37

STOP Stop Output Current Ramp Command

Input: STOP [term]

Remarks: This command will stop the output current ramp within two seconds of sending the command.

To restart the ramp, use the SETI command to set a new output current setpoint.

XPGM External Program Mode Command

Input: XPGM <mode>[term]

Format: n

<mode> 0 = Internal, 1 = External, 2 = Sum.

Example: XPGM 1[term] – Places the Model 642 into external program mode where the output current is set by

an external voltage.

XPGM? External Program Mode Query

Input: XPGM?[term]

Returned: <mode>[term]

Format: n (Refer to command for description)

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5-38 Computer Interface Operation

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Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Options and Accessories 6-1

CHAPTER 6

OPTIONS AND ACCESSORIES

6.0 GENERAL

This chapter provides information on accessories available for the Model 642 Electromagnet Power Supply.

6.1 ACCESSORIES INCLUDED

Part Number Description

MAN-Model 642 Model 642 Electromagnet Power Supply User’s Manual.

6031 Two front handles.

6032 Two rear handles.

6051 Terminal Block, 4 Pin

6052 Terminal Block, 8 Pin

6252 15-pin D-sub mating connector, analog I/O.

108-654 Strain Relief Bushing Kit

– Calibration Certificate.

6.2 ACCESSORIES AVAILABLE

Part Number Description

6201 IEEE-488 Cable Kit, 1 meter (3 foot) IEEE-488 (GPIB) computer interface cable

assembly.

6261 Magnet Cable Kit, 3 meters (10 feet), 60 A, AWG 4.

6262 Magnet Cable Kit, 6 meters (20 feet), 60 A, AWG 4.

6041 Flow Switch.

6042 Solenoid Water Valve with Bracket.

CAL-642-CERT Instrument recalibration with certificate.

CAL-642-DATA Instrument recalibration with certificate and data.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

6-2 Options and Accessories

This Page Intentionally Left Blank

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Service 7-1

CHAPTER 7

SERVICE

7.0 GENERAL

This chapter provides basic service information for the Model 642 Superconducting Magnet Power Supply. Customer

service of the product is limited to the information presented in this chapter. Factory trained service personnel should be

consulted if the instrument requires repair.

7.1 CONTACTING LAKE SHORE CRYOTRONICS

If a Lake Shore product was purchased through a dealer or representative, please use that resource for prompt sales or

service information. When contacting Lake Shore directly, please specify the name of a department if do not know the

name of an individual. Questions regarding product applications, price, availability and shipments should be directed to

sales. Questions regarding instrument calibration or repair should be directed to instrument service. Do not return a

product to Lake Shore without a Return Authorization number. Refer to Paragraph 7.2. Current contact information

can always be found on the Lake Shore web site: www.lakeshore.com.

Mailing Address:

Lake Shore Cryotronics, Inc.

Instrument Service Department

575 McCorkle Blvd.

Westerville, OH USA 43082-8888

E-mail Address: sales@lakeshore.com

service@lakeshore.com

Sales

Instrument Service

Telephone: 614-891-2244

614-891-2243 ext. 131

Sales

Instrument Service

Fax: 614-818-1600

614-818-1609

Sales

Instrument Service

When contacting Lake Shore please provide your name and complete contact information including e-mail address if

possible. It is often helpful to include the instrument model number and serial number (located on the rear panel of the

instrument) as well as the firmware revision information as described in Paragraph 4.21.

7.2 RETURNING PRODUCTS TO LAKE SHORE

If it is necessary to return the Model 642 for recalibration, repair or replacement, a Return Authorization (RA) number

must be obtained from a factory representative or from the Lake Shore web site. Do not return a product to Lake

Shore without an RA number. The following information must be provided to Lake Shore in order to obtain an RA

number.

1. Instrument model and serial number.

2. User name, company, address, phone number, and e-mail address.

3. Malfunction symptoms.

4. Description of the system in which the product is used.

If possible, the original packing material should be retained for reshipment. If not available, a minimum of three inches

of shock adsorbent packing material should be placed snugly on all sides of the instrument placed in a sturdy corrugated

cardboard box. The RA number should be included in the mailing label or written prominently on the outside of the box.

A copy of the customer contact information and RA number should be included inside the box. Consult Lake Shore with

questions regarding shipping and packing instructions.

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7-2 Service

7.3 LINE VOLTAGE SELECTION

The Model 642 may be configured for four basic AC power configurations: 208 VAC, 230 VAC, 380 VAC and 415

VAC. Proper voltage selection must be made before connection to the power mains. Each configuration requires the

appropriate wiring within the power wiring access panel on the rear of the instrument. Nominal line voltages and

appropriate selections are shown in Table 7-1. See Section 3.3.1 for further details. See Figure 7-1 for general locations.

Figure 7-1. Model 642 Rear Panel (shown with wiring cover removed)

Use the following procedure to change the instrument line voltage.

WARNING: To avoid potentially lethal shocks, turn off the power supply and disconnect it from AC power before

performing this procedure.

1. Identify the power wiring access panel on the rear of the Model 642.

2. Turn the front panel line power switch OFF (O).

3. Disconnect the power cable at the plug end for safety.

4. Remove the perimeter screws holding the power wiring access panel.

5. Observe the 4 voltage-selection wires held by the clear plastic wiring guide. See Figure 7-2.

6. Loosen the screw terminals presently holding the four wires.

7. Relocate the 4 wires (using the wiring guide) to the desired voltage position. Refer to Table 7-1.

8. Place the wires into the appropriate screw terminals and tighten.

9. Verify solid, tight screw connections to these four wires.

10. Replace the power wiring access panel using all perimeter screws.

11. Verify the voltage indicator in the window of the power wiring access panel.

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Service 7-3

TERMINAL SCREW

WIRE FERRULE

VOLTAGE SELECTOR CARD

VOLTAGE INDICATOR KEY

Figure 7-2. Voltage Change Detail

7.4 CIRCUIT BREAKER SETTING

The main three-phase input power is protected by an automatic-reset circuit breaker within the instrument. A smaller,

start-up power supply is fused separately and discussed in Section 7.5. If the breaker trips, it will reset within a few

minutes and the unit can be restarted. If the unit trips again after a short time, the circuit breaker trip current may be set

incorrectly. Table 7-1 shows required voltage and current settings.

Table 7-1. Voltage and Current Selection

Nominal Voltage Voltage Tap Circuit Breaker

200 V 204 V 18 A

208 V 204 V 18 A

220 V 225 V 17 A

230 V 225 V 17 A

380 V 380 V 12 A

400 V 408 V 12 A

415 V 408 V 12 A

WARNING: To avoid potentially lethal shocks, turn off the power supply and disconnect it from AC power before

performing this procedure.

CAUTION: For continued protection against fire hazard, use only the recommended current setting for the line

voltage selected.

Use the following procedure to verify or change the circuit breaker current setting.

1. Identify the power wiring access panel on the rear of the Model 642.

2. Turn the front panel line power switch OFF (O).

3. Disconnect the power cable at the plug end for safety.

4. Remove the perimeter screws holding the power wiring access panel.

5. Refer to Figure 7-1 to locate the circuit breaker detailed in Figure 7-3.

6. Lift the circuit breaker setting access door and visually confirm the setting as shown in Figure 7-3.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

7-4 Service

CURRENT SETTING DIALACCESS COVER

Figure 7-3. Circuit Breaker

7. If incorrect, use a small straight blade screwdriver to reset according to Table 7-1.

8. Close the circuit breaker access door.

9. Replace the power wiring access panel using all perimeter screws.

7.5 POWER LINE FUSE REPLACEMENT

The Model 642 uses a low-power, start-up power supply to provide power to the main contactor coil through multiple

thermal safety switches. The start-up supply is energized any time the three-phase power input voltage is connected to

the Model 642. This section deals with the fuses for this supply. If the power line fuses for this supply are open, the

Model 642 internal three-phase contactor will not close and normal operation will not be possible. If the Model 642 is

connected to an input voltage that is higher than the selected voltage of the Model 642, these fuses are expected to clear

and prevent operation of the Model 642. Proper voltage selection must be made before connection to the power mains.

Access to these fuses is through the power wiring access panel.

WARNING: To avoid potentially lethal shocks, turn off the power supply and disconnect it from AC power before

performing this procedure.

CAUTION: For continued protection against fire hazard, replace only with same fuse type and rating specified for

the line voltage selected.

Use the following procedure to change the power line fuses.

1. Identify the power wiring access panel on the rear of the Model 642.

2. Turn the front panel line power switch OFF (O).

3. Disconnect the power cable at the plug end for safety.

4. Remove the perimeter screws holding the power wiring access panel.

5. Locate the two fuse holder assemblies as shown in Figure 7-1 and detailed in Figure 7-4

6. Pull open the access door to remove a fuse.

7. Check the fuse for continuity. Replace fuse(s) if necessary. Fuses should be replaced in pairs. Fuses are inserted

small-end first as shown.

8. Close the fuse access door(s).

9. Replace the wiring access panel using all perimeter screws.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Service 7-5

Figure 7-4. Fuse Holder Detail

7.6 ERROR MESSAGES

The following messages appear on the lower part of the instrument display when it identifies a problem during operation.

The Fault LED will light in conjunction with the error message. A more extensive description of the error message can

shown by pressing the Status key. If the error condition can be immediately cleared, it can be done by pressing the

Status key while in the error status display. Refer to Paragraph 4.14 for a description of the error status display.

Error messages are divided into three groups:

Instrument Hardware Errors are related to internal instrument circuitry. When one of these errors occurs, the Fault

LED is solidly lit, the output setting is set to 0 A, current entry will not be allowed and there is no way to clear the

error unless power is cycled. If one of these error messages persists after power is cycled, the instrument requires

repair. Instrument Hardware Errors are listed in Table 7-2.

Operational Errors are related to instrument operation and do not necessarily indicate a hardware problem. When one

of theses errors occurs, the Fault LED will be blinking and the error condition can be cleared once the fault condition

has been removed. Operational Errors are listed in Table 7-3.

User Errors are related to user requests that cannot be processed. These errors generate responses that immediately

explain the cause of the error. These are usually simple order-of-operation issues and are easily resolved. The fault

LED is not used for these simpler errors. User Errors are self-explanatory and are therefore not listed.

Table 7-2. Instrument Hardware Errors

Internal Temperature Fault

Cold Plate temperature is over 45° C. The output setting is set to 0 A and no current

entry will be allowed. The error message will flash for 10 seconds then the Model 642

will turn itself off.

Output Over Voltage

The output voltage is greater than the 44 V compliance voltage limit indicating a

problem with the compliance voltage circuitry. The output setting is set to 0 A and no

current entry will be allowed. The error message will flash for 10 seconds then the

Model 642 will turn itself off.

Output Over Current

The measured output current exceeded 73 A. The output setting is set to 0 A and no

current entry will be allowed. The error message will flash for 10 seconds then the

Model 642 will turn itself off.

DAC Processor not

Responding

The processor that controls the output DAC is not responding or is responding

incorrectly. The output setting is set to 0 A and no current entry will be allowed.

Cycle power to attempt to clear.

Output Control Failure

One of the internally monitored voltages is beyond an acceptable range on power up.

The output setting is set to 0 A and no current entry will be allowed. Cycle power to

clear attempt to clear.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

7-6 Service

Table 7-3. Operational Errors

Remote Enable Fault

Detected

The Remote Enable connection loop is not closed. The output setting is set to 0 A and

no current entry will be allowed. Once the loop is closed, the error is cleared by pressing

the STATUS key or sending “ERCL” over computer interface.

Power Supply Flow

Switch Fault Detected

The Power Supply Flow Switch connection loop is not closed. The output setting is set

to 0 A and no current entry will be allowed. Once the loop is closed, the error is cleared

by pressing the STATUS key or sending “ERCL” over computer interface.

Magnet Flow Switch Fault

Detected

The Magnet Flow Switch connection loop is not closed. The output setting is set to 0 A

and no current entry will be allowed. Once the loop is closed, the error is cleared by

pressing the STATUS key or sending “ERCL” over computer interface.

High Line Voltage

Detected

The Output Stage Voltage (Out Stg V) is greater than 66 V. The most likely cause is a

power mains voltage that is too high. This error will clear when the power mains voltage

is within specified tolerances. Continued operation is allowed but may not be optimal.

Low Line Voltage

Detected

The Output Stage Voltage (Out Stg V) is less than 44 V. The most likely cause is a

power mains voltage that is too low. This error will clear when the power mains voltage

is within specified tolerances. Continued operation is allowed but may not be optimal.

Internal Temperature High

Cold Plate temperature is over 40° C. The output setting is set to 0 A and no current

entry will be allowed. The error will clear when the Cold Plate temperature falls below

40° C. This may be indicative of low cooling water flow or high water temperature.

External Current Program

Error

The instrument was not allowed to change to external or sum current programming

modes (including power-up) because the programming voltage was greater than

0.025 V. This error can be cleared when the programming voltage is less than 0.025 V

or the instrument is changed to internal current programming mode.

Calibration Invalid

The instrument has either not been calibrated or calibration data has been corrupted.

This error can be cleared at any time by pressing both ESC and ENTER keys on the

keypad simultaneously. The instrument can still be used in this state but there is no

guarantee that it is operating within specifications. The instrument must be recalibrated

to properly correct this error condition.

7.7 ELECTROSTATIC DISCHARGE

Electrostatic Discharge (ESD) may damage electronic parts, assemblies, and equipment. ESD is a transfer of electrostatic

charge between bodies at different electrostatic potentials caused by direct contact or induced by an electrostatic field.

The low-energy source that most commonly destroys Electrostatic Discharge Sensitive (ESDS) devices is the human

body, which generates and retains static electricity. Simply walking across a carpet in low humidity may generate up to

35,000 volts of static electricity.

Current technology trends toward greater complexity, increased packaging density, and thinner dielectrics between

active elements, which results in electronic devices with even more ESD sensitivity. Some electronic parts are more

ESDS than others. ESD levels of only a few hundred volts may damage electronic components such as semiconductors,

thick and thin film resistors, and piezoelectric crystals during testing, handling, repair, or assembly. Discharge voltages

below 4000 volts cannot be seen, felt, or heard.

7.7.1 Identification of Electrostatic Discharge Sensitive Components

The following are various industry symbols used to label components as ESDS.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Service 7-7

7.7.2 Handling Electrostatic Discharge Sensitive Components

Observe all precautions necessary to prevent damage to ESDS components before attempting installation. Bring the

device and everything that contacts it to ground potential by providing a conductive surface and discharge paths. As a

minimum, observe these precautions:

1. De-energize or disconnect all power and signal sources and loads used with unit.

2. Place unit on a grounded conductive work surface.

3. Ground the technician through a conductive wrist strap (or other device) using 1 MΩ series resistor to protect

operator.

4. Ground any tools, such as soldering equipment, that will contact unit. Contact with operator's hands provides a

sufficient ground for tools that are otherwise electrically isolated.

5. Place ESDS devices and assemblies removed from a unit on a conductive work surface or in a conductive container.

An operator inserting or removing a device or assembly from a container must maintain contact with a conductive

portion of the container. Use only plastic bags approved for storage of ESD material.

6. Do not handle ESDS devices unnecessarily or remove from the packages until actually used or tested.

7.8 ENCLOSURE TOP PANEL REMOVAL AND REPLACEMENT

WARNING: To avoid potentially lethal shocks, set current output to 0 A, turn off the power supply, and disconnect

it from AC power line before performing this procedure. Only qualified personnel should perform this

procedure.

7.8.1 Removal

1. Set power switch to Off (O) and disconnect power cord from the power outlet.

2. Remove the Model 642 from rack (if necessary) to gain easy access to the top panel.

3. Remove and retain the 17 flat-head Phillips screws securing the top panel of the Model 642.

4. Remove and retain the two truss-head Phillips screws and nylon washers from the top edge of the front panel that

secure the top panel to the front panel.

5. Carefully remove the top panel from the unit.

7.8.2 Installation

1. Replace the top panel on the Model 642 with the folded lip of the panel toward the front of the unit.

2. Replace and secure the 17 flat-headed Phillips screws. Do not use excessive torque.

3. Replace the two Phillips head screws securing the top panel lip to the top edge of the front panel.

4. Replace the Model 642 in the rack (if used)

5. Reconnect the Model 642 to the power outlet. Apply power via the front panel button (l).

7.9 FIRMWARE REPLACEMENT

There are two integrated circuits (IC) that may potentially require replacement. See Figure 7-6 for respective locations.

• Main Firmware Erasable Programmable Read Only Memory (EPROM) (U35) – Contains the user interface software.

Has a sticker on top labeled “MModel 642F.HEX” and a date.

• DAC Microcontroller (U51) – Contains software that controls the output DAC. Has a sticker on top labeled “MModel

642DACF.HEX” and a date.

Use the following procedure to replace either or both of these ICs.

1. Follow the top of enclosure removal procedure of Section 7.8.1.

2. Refer to Figure 7-5 and locate the Digital Board assembly.

3. Disconnect the housekeeping transformer connector from J-1.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

7-8 Service

Firmware Replacement (Continued)

4. Disconnect the ribbon cable to the Analog Board assembly from J-2.

5. Disconnect the cable to the fan from J-3.

6. Disconnect the ribbon cable to the Keypad Board assembly from J-4.

7. Disconnect the main transformer connector from J-7.

8. Remove all connections from the IEEE-488, RS232C, Power Supply, Auxiliary, and Magnet Water connectors on

the back of the Model 642.

9. Remove and retain the hexagonal mounting standoffs from the IEEE-488 and RS232C connectors on the back of the

Model 642.

10. Locate, remove and retain the two 6-32 pan-head machine screws holding the Digital Board in place. See Figure 7-6.

11. Remove the Digital Board by pulling it toward the front to clear the rear connectors from their back panel holes and

then carefully lifting the Board assembly out of the unit.

12. Locate the appropriate IC(s) on the main circuit board. See Figure 7-6. Note orientation of existing IC.

CAUTION: The ICs are Electrostatic Discharge Sensitive (ESDS) devices. Wear shock-proof wrist straps (resistor

limited to <5 mA) to prevent injury to service personnel and to avoid inducing an Electrostatic

Discharge (ESD) into the device.

13. Use IC puller to remove existing IC(s) from the socket.

14. Noting orientation of new IC(s), use an IC insertion tool to place new device(s) into socket(s). Ensure that no pins

are allowed to bend.

15. Reinstall the Digital Board into the unit taking care to properly locate the bottom edge of the board between the four

locator pins on the bottom of the instrument. Push the Digital Board carefully rearward taking care to locate the rear

connectors through the rear panel of the unit.

16. Attach the Digital Board using the two 6-32 pan-head Phillips screws removed earlier.

17. Remount the IEEE-488 and RS232C connectors using the hexagonal mounting standoffs removed earlier.

18. Reinstall all appropriate rear panel connections that were removed earlier. Take care NOT to interchange the

“Magnet” and “Power Supply” connectors.

19. Reinstall all Digital Board connections removed earlier. See Figure 7-6

20. Recheck that all connectors have been reinstalled and confirm proper locations and orientations of each.

21. Follow the top of enclosure installation procedure of Section 7.8.2.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Service 7-9

DIGITAL BOARD

Figure 7-5. Board Locations (top view)

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

7-10 Service

VR1

R74

C67

CR18

AUXILIARY

C131

CR10

R73

VR3

C132

J10

MAGNET

C130

R71

VR2

CR9

R78 J8

LOCATOR PINS

TP6

U13

C43

R52

R23

C29 R32 C21

R22

R29

R17

R28

R18

R24

R13

C30

IRDG

CR4

U15

R45

C45

C62

R55

TP8

CR5

CR6

U16

R46

R48

R42

C63

CR7

C111

C75

U48

C103

C107

U34

C91 C93

C72

U47

U35

C102

C92

C105

U41

U33

C86

IEEE CONNECTOR

C122

C121

C120

C119

C118

C117

C108

C116

U49

R69

C24

R30 R34

C25

GND2

R20

R31

C26

C36TP4

C57

I DAC OUT

U20

C38

C42 R50

C56

C49

R43

C50

TP10

R56

CR3

C40

C53

C13

U25

U52

C104

C70

U27

R64

A/D 2 IN

TP9

C61

U42

C94

R65

U45

R67

U36

R66

TP7

C87

A/D 1 IN C79 C83

U31

C80

C84

U32

C76

C97 C96

C106

C98

U37

U51

R70

TEST

C112

RUN

JMP1

C109

R54

R53

C23

R41

U21

C54

U26

R11 R10

J4 GND2

KEYPAD PCB

R5 R7

TP2

C10

R14

R12

C44

VRDG

R33

U10

R27

C18 R16

U14

R44

C32

U22

R68

SP1

C124

U46

C125

RS232C

C114

U50

C127 J5

MOUNTING SCREWS

R58 VREF

HOUSEKEEPING TRANSFORMER SECONDARIES

MAIN TRANSFORMER

FAN

R80

C11

C52

ANALOG PCB

C27

U24

U17

C31

C39 TP5

R15

R26

R25

R21

U19

R19

R49

C55

C113

C81

C73

C123

R60

+5(1) GND 1

642 DIGITAL PCB

c 2006 LSCI

111-278 /A

TP3 TP1

C51

C16

C17

C37

R37

C22

R36

U12

R39

U18

R47

R40

R51

C60

ACAC ACAC

CR1

ACAC

R38

C19

C46

R79

C47

C48

R35

C34

C28

C33

U23

C41

CR17

ACAC

CR2

ACACACAC

R62

R63

C58

CR15

R61

CR16

R59

F10

U55

U39

C88

C85

U38

C100

C99

C77

U30

C89

C78

C90

U40

C95

SUPPLY

POWER

U53

C126

C128

U54

C129

CR11

R77

Figure 7-6. Digital Board Parts Locations

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Service 7-11

7.10 CONNECTOR AND CABLE DEFINITIONS

All non-power electrical connections to the rear of the Model 642 are detailed in this section.

7.10.1 Analog I/O Connector

The Analog I/O connector provides the connections for the External Programming voltage as well as Analog

representations of the current and voltage output levels. Although these inputs/outputs are electronically balanced to

minimize ground loops, the common-mode voltage should not exceed 5 V on the outputs and 2 V on the input.

Pin Name Pin Name

Chassis-common

Current Program –

Chassis-common

Voltage Monitor –

Chassis-common

Current Monitor –

Chassis-common

Current Program +

Chassis-common

Voltage Monitor +

Chassis-common

Current Monitor +

Figure 7-7. ANALOG I/O Connector Details

7.10.2 Magnet Connector

The Magnet Water connector provides the means to connect a water control valve (24 VAC) and an associated water

flow switch (closed during flow) to protect the magnet from loss of water flow. Pins 1 & 2 must be closed for normal

operation. Pins 3 & 4 supply 24 VAC at 1 A for operation of a water control valve.

Pin Name

1 Flow Switch (Com)

2 Flow Switch

3 Magnet Water Valve A

4 Magnet Water Valve B

Figure 7-8. Magnet Connector Details

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7-12 Service

7.10.3 Auxiliary Connector

The Auxiliary Connector provides connections for three functions:

1. Emergency Stop – This normally-closed circuit turns off power to the Model 642 just as if the OFF (O) button was

pressed on the front panel when opened. Normal operation requires a closed connection between the pins.

2. Fault Relay – The fault relay can be used to communicate the presence of a Model 642 fault to external equipment.

The relay follows the operation of the Fault light on the front panel. Both normally-open and normally-closed

configurations are provided. The contacts are electrically isolated from the Model 642 chassis.

3. Remote Enable – These contacts are similar in function to the flow switch inputs. Normal (enabled) operation

requires a closed connection between the pins.

Pin Name

1 Emergency Stop A

2 Emergency Stop B

3 Chassis-common

4 Fault-NO

5 Fault-Com

6 Fault-NC

7 Chassis-common

8 Remote Enable

Figure 7-9. Auxiliary Connector Details

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Service 7-13

7.10.4 Power Supply Connector

The Power Supply connector provides the means to connect a water control valve (24 VAC) and an associated water

flow switch (closed during flow) to protect the Model 642 from loss of water flow. Pins 1 & 2 must be closed for normal

operation. Pins 3 & 4 supply 24 VAC at 1 A for operation of a water control valve.

Pin Name

1 Flow Switch (Com)

2 Flow Switch

3 Power Supply Water Valve A

4 Power Supply Water Valve B

Figure 7-10. Power Supply Connector Details

7.10.5 RS-232C Serial Interface Connector

This connector provides one of two means of computer interface. Command descriptions are found in Section 5.

Model 642 Electromagnet Power Supply Typical Computers

DE-9P (DTE) DB-25P (DTE) DE-9P (DTE)

Pin Description Pin Description Pin Description

1 NC 2 TD (out) 1 DCD (in)

2 Receive Data (RD in) 3 RD (in) 2 RD (in)

3 Transmit Data (TD out) 4 RTS (out) 3 TD (out)

4 Data Terminal Ready (DTR out) 5 CTS (in) 4 DTR (out)

5 Chassis-common 6 DSR (in) 5 GND

6 Data Set Ready (DSR in) 7 GND 6 DSR (in)

7 Data Terminal Ready (DTR out) (tied to 4) 8 DCD (in) 7 RTS (out)

8 NC 20 DTR (out) 8 CTS (in)

9 NC 22 Ring in (in) 9 Ring in (in)

Figure 7-11. RS232C (DTE) Connector Details

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

7-14 Service

7.10.6 Serial Interface Cable Wiring

The following are suggested cable wiring diagrams for connecting the Model 642 Serial Interface to various Customer

Personal Computers (PCs).

Model 642 to PC Serial Interface – PC with DE-9P

Model 642 DE-9P Standard Null-Modem Cable (DE-9S to DE-9S) PC DE-9P

5 - GND 5 - GND

2 - RD (in) 3 - TD (out)

3 - TD (out) 2 - RD (in)

4 - DTR (out) 6 - DSR (in)

6 - DSR (in) 4 - DTR (out)

1 - NC 7 - RTS (out)

7 - DTR (tied to 4) 8 - CTS (in)

8 - NC 1 - DCD (in)

Model 642 to PC Serial Interface – PC with DB-25P

Model 642 DE-9P Standard Null-Modem Cable (DE-9S to DB-25S) PC DB-25P

5 - GND 7 - GND

2 - RD (in) 2 - TD (out)

3 - TD (out) 3 - RD (in)

1 - NC 4 - RTS (out)

7 - DTR (tied to 4) 5 - CTS (in)

8 - NC 8 - DCD (in)

6 - DSR (in) 20 - DTR (out)

4 - DTR (out) 6 - DSR (in)

Model 642 to PC Interface using Null Modem Adapter

Model 642 DE-9P Null Modem Adapter PC DE-9P

5 - GND 5 - GND

2 - RD (in) 3 - TD (out)

3 - TD (out) 2 - RD (in)

1 – NC (out) 4 - DTR

6 - DSR (in) 1 - DCD (in)

4 - DTR (out) 6 - DSR (in)

7 - DTR (tied to 4) 8 - CTS (in)

8 - NC 7 - RTS (out)

9 - NC 9 - NC

NOTE: Same as null modem cable design except PC CTS is provided from the Model 642 on DTR.

7.10.7 IEEE-488 Parallel Interface Connector

Connect to the IEEE-488 Interface connector on the Model 642 rear with cables specified in the IEEE-488-1978 standard

document. The cable has 24 conductors with an outer shield. The connectors are 24-way Amphenol 57 Series (or

equivalent) with piggyback receptacles to allow daisy-chaining in multiple device systems. The connectors are secured in

the receptacles by two captive locking screws with metric threads. The total length of cable allowed in a system is 2

meters for each device on the bus, or 20 meters maximum. The Model 642 can drive a bus of up to 10 devices. A

connector extender is required to use the IEEE-488 Interface and Relay Terminal Block at the same time. Figure 7-12

shows the IEEE-488 Interface connector pin and signal names as viewed from the Model 642 rear panel.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Service 7-15

Pin Symbol Description

DIO 1

DIO 2

DIO 3

DIO 4

EOI

DAV

NRFD

NDAC

IFC

SRQ

ATN

SHIELD

DIO 5

DIO 6

DIO 7

DIO 8

REN

GND 6

GND 7

GND 8

GND 9

GND 10

GND 11

GND

Data Input/Output Line 1

Data Input/Output Line 2

Data Input/Output Line 3

Data Input/Output Line 4

End Or Identify

Data Valid

Not Ready For Data

Not Data Accepted

Interface Clear

Service Request

Attention

Cable Shield

Data Input/Output Line 5

Data Input/Output Line 6

Data Input/Output Line 7

Data Input/Output Line 8

Remote Enable

Ground Wire – Twisted pair with DAV

Ground Wire – Twisted pair with NRFD

Ground Wire – Twisted pair with NDAC

Ground Wire – Twisted pair with IFC

Ground Wire – Twisted pair with SRQ

Ground Wire – Twisted pair with ATN

Logic Ground

Figure 7-12. IEEE-488 Connector Details

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

7-16 Service

7.11 CALIBRATION

Lake Shore maintains a fully automated calibration fixture for the Model 642 that measures existing performance of the

unit and then recalibrates the using NIST traceable resistance and voltage standards. In addition, non-calibration features

are verified for proper operation by a full battery of extensive tests. Although this testing is very complete, it requires the

return of the Model 642 to Lake Shore to perform the recalibration. In some instances, however, it may be necessary to

recalibrate the Model 642 in the field. Calibration information for the following operating parameters is provided:

• Output Current.

• Output Current Reading

• Output Voltage Reading

• External Programming Voltage Reading

These calibrations are done through the computer interface and the calibration constants are stored in the non-volatile

memory in the instrument. The cover does not have to be removed to calibrate the instrument. The remaining features of

the Model 642 do not require calibration to operate within their specified tolerances.

Uncalibrated (default) values for gains are 1 while offsets are 0. Operation with these values is possible but the accuracy

will be reduced to as much as ±2% of full scale, generally. If the Model 642 is used in closed loop operation and

programmed through the external input, regular calibration may not be required.

7.11.1 Calibration Interface

Computer interface commands are included in the Model 642 specifically for calibration. These commands work with

either the IEEE-488 or RS-232C interface. Refer to Section 7.13.4 for a complete description of each calibration

command.

It is always recommended to read out old calibration coefficients using the CALZ? and CALG? interface queries before

attempting to calibrate. This will give the operator experience with the interface command, data formatting, and typical

values. If the old values are saved, they can be reloaded in the case of accidental loss of data during calibration. New

calculated calibration coefficients should be very similar to the old values. Discrepancy between the old and new values

of more than 0.1% of gain calibration coefficients or 0.1% of range for zero coefficients could indicate an error in the

calibration procedure or a hardware failure. Do not attempt to recalibrate a damaged instrument.

The instrument will use the new calibration coefficients as soon as they are sent with the either the CALZ or CALG

interface command but they are not saved permanently until the CALSAVE command is issued. If a mistake is made in

the calibration process, turn the instrument power off and on again before CALSAVE is issued to restore the old

calibration constants. Once CALSAVE is issued, old values cannot be retrieved from the instrument.

If calibration coefficients are left at default or are outside of the normal calibration range, the following error message

will appear in the instrument display when the instrument is turned on: “Calibration Invalid”. This error message must be

bypassed to allow calibration of the instrument. Press both Enter and Escape keys simultaneously to bypass the error

message. Operation in this state is possible but at least one calibration is known to be out of proper range and

measurement is likely to be erroneous.

Simple communications program examples are shown in Sections 5.1.5.2 and 5.2.7.1. Some time should be spent

becoming familiar with the calibration commands before beginning a calibration. Although the calibration factors are

sent to the Model 642 over the computer interface, this procedure is written to obtain the Model 642 readings solely by

visual observation of the front panel.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Service 7-17

7.11.2 Calibration Equipment

1. Calibration Shunt Resistor – The output current of the Model 642 must be measured externally as the primary

reference for calibration. When current is measured, it is the result of the current through the known resistance of the

calibration resistor. This resistor must be accurately measured and its actual value (R Shunt) used to determine the

actual current flow. For example, if the resistor is measured at 0.99661 mΩ, the actual current flowing is calculated

by the following equation.

Ishunt = Vshunt/0.99661 × 10-3 or Ishunt = 1000 × Vshunt/0.99661

This resistor must withstand the full current of the Model 642 and do so with a minimum of heating that can easily

change the resistance and therefore the current measurement. At 70 A, this resistor only dissipates 4.9 W. Even so, it

is highly recommended to mount the resistor on a heat sink with forced air-cooling to minimize temperature rise and

related value changes during calibration. (Alpha PSBWR0010F is suggested)

2. Magnet Load – The Model 642 is designed for a nominal magnet load of 0.5-ohms and 0.5 H. For calibration

purposes, the magnet can easily be used as the calibration load. The calibration shunt resistor is wired in series with

the positive output terminal using a cable of similar current handling capability as the normal magnet lines. An

alternative to this is the use of a resistor bank with total resistance of 0.5-ohms capable of safely dissipating 2,450 W

of heat (the equivalent of a medium sized space heater). This procedure assumes the use of the water-cooled magnet

as a calibration load.

3. DC Voltmeter (DVM) – The voltmeter must measure VDC accurately to 10’s of µV if resolution to 10’s of mA

(from the Model 642). The Agilent Model 34401 DMM or better is suggested.

7.11.3 Calibration Procedure

The following calibration steps should be performed exactly in the order provided. Pay close attention to the use of

“CALZ” vs “CALG” commands. They can easily be confused and will certainly create unexpected results if accidentally

interchanged. Zeroing calibrations use “CALZ” commands while Gain (Span) calibrations use “CALG” commands.

7.11.3.1 Calibrate Current Output Zero

The 1 mΩ shunt resistor is wired in series with the calibration load from the positive output terminals with #4 AWG

wire. Cable length is relatively unimportant but should be less than 5 feet to the shunt resistor. Voltage across the shunt

resistor is to be monitored by the DVM. The DVM input connections must both be isolated from earth (power line)

ground.

1. Send “CALZ 10, 0” to set the output offset constant to 0.

2. Set the Model 642 output current to 0 A.

3. Measure the actual voltage across the shunt and record (Vshunt).

4. Calculate the zero offset constant: -(Vshunt/Rshunt).

5. Send “CALZ 10, zero offset constant”.

6. Reset the Model 642 output current to 0 A (loads the new offset setting).

7. Verify the actual output current to be less than ±1 mA.

8. Send “CALSAVE” to write this calibration to non-volatile memory.

7.11.3.2 Calibrate Current Reading Zero

1. Send “CALZ 0, 0” to set the current reading offset constant to 0.

2. Measure the actual voltage across the shunt and record (Vshunt).

3. Get the Model 642 output current reading (by front panel or interface) and record (I reading).

4. Calculate the zero offset constant: – (Ireading – (Vshunt/Rshunt)).

5. Send “CALZ 0, zero offset constant”.

6. Verify the Model 642 output current reading to match the actual output current within ±0.0005 mA.

7. Send “CALSAVE” to write this calibration to non-volatile memory.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

7-18 Service

7.13.3.3 Calibrate Output Voltage Reading Zero

This step assumes that the previous two steps are successful and the current through the shunt resistor is quite low

resulting in virtually no voltage across the Model 642 output terminals.

1. Send “CALZ 5, 0” to set the current reading offset constant to 0.

2. Get the Model 642 output voltage reading (by front panel or interface).

3. Calculate zero offset constant: – (output voltage reading).

4. Send “CALZ 5, zero offset constant”.

5. Verify the Model 642 output voltage reading to be 0 ±0.001 V.

6. Send “CALSAVE” to write this calibration to non-volatile memory.

7.11.3.4 Calibrate External Programming Voltage Reading Zero

1. Short the external current programming input lines (pins 3 and 11 of the Analog I/O connector).

2. Send “CALZ 7, 0”. To set the external programming voltage reading constant to 0.

3. Get the Model 642 external programming voltage reading.

NOTE: To get this reading from the Model 642, press and hold the Status key on the front panel until the display

goes dark (≈3 seconds). When the key is then released, a diagnostics display will be seen. The upper right

reading, “EXT PROG”, is the reading needed for this step.

4. Calculate zero offset constant: – (external programming voltage reading).

5. Send “CALZ 7, zero offset constant”.

6. Verify the Model 642 external programming voltage reading to be 0 ±0.0001 V.

7. Send “CALSAVE” to write this calibration to non-volatile memory.

7.11.3.5 Calibrate Output Current Gain (Span)

This calibration is the most difficult and most important of the procedure. It first requires measuring the span of the trim

range (which changes from unit to unit within 1 – 2%) to determine the trim adjustment range that corresponds to a

100% calibration trim change. In other words, we adjust the calibration in % from –100% to +100% but the size of the

calibration trim range changes slightly for each unit. We first measure the span of the calibration trim range and then

measure the full span of the instrument with the calibration trim set to 0%. We have adopted the use of % as the unit

name for the trim calibration since it corresponds to only the percent of trim range and not the full span of the

instrument.

The 65 A set point for calibration is chosen because the maximum trim range at 70 A forces the current past the 70.1 A

internal analog limit and therefore creates significant error. The shunt resistor remains connected in series with the

magnet load for this procedure.

1. Send “CALG 10, 0”. To set the output current gain trim constant to 0.

2. Set the Model 642 output current to +65 A (ramp rate 30 A/s nominal).

3. Wait 30 seconds for settling.

4. Measure the actual voltage across the shunt and record (Vshunt).

5. Calculate and record (Imax): Vshunt/Rshunt.

6. Send “CALG 10, –100”. To set the output current gain trim constant to maximum.

7. Wait 10 seconds.

8. Measure the actual voltage across the shunt and record (Vshunt).

9. Calculate and record (Imaxpostrim): Vshunt/Rshunt.

10. Send “CALG 10, +100”. To set the output current gain trim constant to minimum.

11. Wait 10 seconds.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Service 7-19

Calibrate Output Current Gain (Continued)

12. Measure the actual voltage across the shunt and record (Vshunt).

13. Calculate and record (Iminpostrim): Vshunt/Rshunt.

14. Send “CALG 10, 0”. To set the output current gain trim constant to 0.

15. Set the Model 642 to –65A V (ramp rate 30 A/s nominal).

16. Wait 30 seconds for settling.

17. Measure the actual voltage across the shunt and record (Vshunt).

18. Calculate and record (Imin): Vshunt/Rshunt.

19. Send “CALG 10, –100”. To set the output current gain trim constant to maximum.

20. Wait 10 Seconds.

21. Measure the actual voltage across the shunt and record (Vshunt).

22. Calculate and record (Imaxnegtrim): Vshunt/Rshunt.

23. Send “CALG 10, +100”. To set the output current gain trim constant to minimum.

24. Wait 10 seconds.

25. Measure the actual voltage across the shunt and record (Vshunt).

26. Calculate and record (Iminnegtrim): Vshunt/Rshunt.

27. Send “CALG 10, 0”. To return the output current gain trim constant to 0.

28. Set the Model 642 output current to 0 A.

29. Calculate the gain constant per the following equation:

Current Output Gain Constant = 200((Imax-Imin) – 130)/((Imaxpostrim-Iminpostrim) – (Imaxnegtrim-Iminnegtrim))

30. Send “CALG 10, gain constant”.

This method, while somewhat lengthy, averages the trim spans between negative and positive settings to split the error

between positive and negative operation.

This gain calibration may shift the initial zero calibration for the Current Output DAC slightly. It is best to repeat the

current zero calibrations at this point.

31. Recalibrate Current Output Zero (refer to Section 7.13.3.1).

32. Recalibrate Current Reading Zero (refer to Section 7.13.3.2).

33. Set the Model 642 output current to 65 A (ramp rate 30 A/s nominal).

34. Wait 30 seconds.

35. Measure the actual voltage across the shunt and record (Vshunt).

36. Calculate and record (Iout+): Vshunt/Rshunt.

37. Verify Iout = 65 A ±0.010 A (0.015%).

39. Set the Model 642 output current to –65 A (ramp rate 30 A/s nominal).

40. Wait 30 seconds.

41. Calculate and record (Iout–): Vshunt/Rshunt.

42. Verify Iout = –65 A ±0.010 A (0.015%).

43. Set the Model 642 output current to 0 A.

44. Send “CALSAVE” to write this calibration to non-volatile memory.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

7-20 Service

7.13.3.6 Calibrate Current Reading Gain

1. Send “CALG 0, 1”. To set the output current reading gain constant to 1.

2. Set the Model 642 output current to –70 A. (Ramp rate 30 A/s nominal).

3. Wait 30 seconds.

4. Measure the actual voltage across the shunt and record (Vshunt).

5. Calculate and record (Imeasuredneg): Vshunt/Rshunt.

6. Get the Model 642 output current reading (by front panel or interface) and record (Ireadingneg).

7. Set the Model 642 output current to +70 A (Ramp rate 30 A/s nominal).

8. Wait 30 seconds.

9. Measure the actual voltage across the shunt and record (Vshunt).

10. Calculate and record (Imeasuredpos): Vshunt/Rshunt.

11. Get the Model 642 output current reading (by front panel or interface) and record (Ireadingpos).

12. Calculate gain constant per the following equation:

Current Reading Gain Constant = (Imeasuredpos – Imeasuredneg)/(Ireadingpos – Ireadingneg)

13. Verify gain factor to be 1, ±0.02.

14. Send “CALG 0, gain constant”.

15. Verify the Model 642 output current reading to equal Imeasuredpos, ±0.010 A.

16. Set the Model 642 output current to 0 A.

17. Send “CALSAVE” to write this calibration to non-volatile memory.

This method is somewhat lengthy, but averages the differences between positive (+) and negative (–) excursions.

7.11.3.7 Calibrate Voltage Reading Gain

1. Send “CALG 5, 1”. To set the output voltage reading gain constant to 1.

2. Set the Model 642 output current to 65 A.

3. Wait 30 seconds.

4. Measure the Model 642 actual output voltage at the output terminals and record (Vmeasuredpos).

5. Get the Model 642 output voltage reading (by front panel or interface) and record (Vreadingpos).

6. Set the Model 642 output current to –65 A.

7. Wait 30 seconds.

8. Measure the Model 642 actual output voltage at the output terminals and record (Vmeasuredneg).

9. Get the Model 642 output voltage reading (by front panel or interface) and record (Vreadingneg).

10. Calculate gain constant per the following equation:

Voltage Reading Gain Constant = (Vmeasuredpos -Vmeasuredneg)/(Vreadingpos -Vreadingneg)

11. Verify the gain factor to be 1, ±0.02.

12. Send “CALG 5, gain constant”.

13. Verify the Model 642 output voltage reading to match the actual output voltage within, ±0.001 V.

14. Set the Model 642 output current to 0 A.

15. Send “CALSAVE” to write this calibration to non-volatile memory.

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Service 7-21

7.11.3.8 Calibrate External Current Programming Voltage Reading Gain

This procedure calibrates only the input voltage reading of the External Programming Input. The actual current output

from this input is specified to a 1% tolerance and is not adjustable. It is NOT necessary to engage the External

Programming feature of the Model 642 for this calibration.

1. Connect a new 9 V alkaline battery to the external current programming input lines (positive to positive input).

2. Send “CALG 7, 1”. To set the external programming voltage reading gain constant to 1.

3. Get the Model 642 external programming voltage reading and record (Vreading).

NOTE: To get this reading from the Model 642, press and hold the Status key on the front panel until the display

goes dark (~3 seconds). When the key is then released, a diagnostics display will be seen. The upper right

reading, “Ext Prog”, is the reading needed for this step.

4. Measure the voltage directly across the 9 V battery and record (Vmeasured)

5. Calculate the gain constant per the following equation:

Programming Voltage Reading Gain Constant = Vmeasured/Vreading

6. Verify the gain constant to be 1, ±0.05.

7. Send “CALG 7, constant”.

8. Verify the Model 642 external programming voltage reading to match the measured 9 V battery voltage within,

±0.0005 V.

9. Send “CALSAVE” to write this calibration to non-volatile memory.

7.11.4 Calibration-Specific Interface Commands

The following interface commands are only used during calibration and are in addition to those listed in Chapter 5.

CALG Gain Calibration Constant Command

Input: CALG <type>, <value>[term]

Format: nn, ±nnnnnnn

<input> Specifies the item to calibrate. Valid entries are:

0 = Output I Reading

1 = Bias A Reading *

2 = Bias B Reading *

3 = Gnd Diff Reading *

4 = Out Con Reading *

5 = Output V Reading

6 = Boost V Reading*

7 = Ext Prog Input Reading

8 = Temp Reading*

9 = Out Stg V Reading *

10 = Actual Output Current

<value> Gain calibration constant value.

Remarks: Items marked with a * are for internal diagnostic use only and should always be set

to a value of 1 (default).

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7-22 Service

CALG? Gain Calibration Constant Query

Input: CALG? <type>[term]

Format: nn

<type> 0 – 10.

Returned: <value>[term]

Format: ±nnnnnnn (Refer to command for description)

CALSAVE Calibration Save Command

Input: CALSAVE[term]

Remarks: Saves all CALZ and CALG calibration constants in non-volatile memory.

CALZ Zero Offset Calibration Constant Command

Input: CALZ <type>, <value>[term]

Format: nn, ±nnnnnnn

<type> Specifies the item to calibrate. Valid entries are:

0 = Output I Reading

1 = Bias A Reading *

2 = Bias B Reading *

3 = Gnd Diff Reading *

4 = Out Con Reading *

5 = Output V Reading

6 = Boost V Reading*

7 = Ext Prog Input Reading

8 = Temp Reading*

9 = Out Stg V Reading *

10 = Actual Output Current

<value> Zero offset calibration constant value.

Remarks: Items marked with a * are for internal diagnostic use only and should always be set

to a value of 0 (default).

CALZ? Zero Offset Calibration Constant Query

Input: CALZ? <type>[term]

Format: nn

<type> 0 – 10.

Returned: <value>[term]

Format: ±nnnnnnn (Refer to command for description)

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Glossary of Terminology A-1

APPENDIX A

GLOSSARY OF TERMINOLOGY

accuracy. The degree of correctness with which a measured value agrees with the true value.2

electronic accuracy. The accuracy of an instrument independent of the sensor.

sensor accuracy. The accuracy of a temperature sensor and its associated calibration or its ability to match a standard curve.

American Standard Code for Information Interchange (ASCII). A standard code used in data transmission, in which

128 numerals, letters, symbols, and special control codes are represented by a 7-bit binary number as follows:

American Wire Gage (AWG). Wiring sizes are defined as diameters in inches and millimeters as follows:

AWG Dia. In. Dia. mm AWG Dia. In. Dia. mm AWG Dia. In. Dia. mm AWG Dia. In. Dia. mm

1 0.2893 7.348 11 0.0907 2.304 21 0.0285 0.7230 31 0.0089 0.2268

2 0.2576 6.544 12 0.0808 2.053 22 0.0253 0.6438 32 0.0080 0.2019

3 0.2294 5.827 13 0.0720 1.829 23 0.0226 0.5733 33 0.00708 0.178

4 0.2043 5.189 14 0.0641 1.628 24 0.0207 0.5106 34 0.00630 0.152

5 0.1819 4.621 15 0.0571 1.450 25 0.0179 0.4547 35 0.00561 0.138

6 0.1620 4.115 16 0.0508 1.291 26 0.0159 0.4049 36 0.00500 0.127

7 0.1443 3.665 17 0.0453 1.150 27 0.0142 0.3606 37 0.00445 0.1131

8 0.1285 3.264 18 0.0403 1.024 28 0.0126 0.3211 38 0.00397 0.1007

9 0.1144 2.906 19 0.0359 0.9116 29 0.0113 0.2859 39 0.00353 0.08969

10 0.1019 2.588 20 0.0338 0.8118 30 0.0100 0.2546 40 0.00314 0.07987

ambient temperature. The temperature of the surrounding medium, such as gas or liquid, which comes into contact with the

apparatus.1

ampere. The constant current that, if maintained in two straight parallel conductors of infinite length, of negligible circular cross

section, and placed one meter apart in a vacuum, would produce between these conductors a force equal to 2 × 10–7 newton per

meter of length.2 This is one of the base units of the SI.

ampere-turn. A MKS unit of magnetomotive force equal to the magnetomotive force around a path linking one turn of a conducting

loop carrying a current of one ampere; or 1.26 gilberts.

ampere/meter (A/m). The SI unit for magnetic field strength (H). 1 ampere/meter = 4π/1000 oersted ≈0.01257 oersted.

analog controller. A feedback control system where there is an unbroken path of analog processing between the feedback device

(sensor) and control actuator (heater).

analog data. Data represented in a continuous form, as contrasted with digital data having discrete values.1

analog output. A voltage output from an instrument that is proportional to its input. For example, from a digital voltmeter, the output

voltage is generated by a digital-to-analog converter so it has a discrete number of voltage levels.

autotuning. In Lake Shore instruments, the Autotuning algorithm automatically determines the proper settings for Gain

(Proportional), Reset (Integral), and Rate (Derivative) by observing the time response of the system upon changes in setpoint.

B. Symbol for magnetic flux density. See Magnetic Flux Density.

bar. Unit of pressure equal to 105 pascal, or 0.98697 standard atmosphere.

Baud. A unit of signaling speed equal to the number of discrete conditions or signal events per second, or the reciprocal of the time of

the shortest signal element in a character.2

bit. A contraction of the term “binary digit”; a unit of information represented by either a zero or a one.2

BNC. Bayonet Nut Connector.

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A-2 Glossary of Terminology

boiling point. The temperature at which a substance in the liquid phase transforms to the gaseous phase; commonly refers to the

boiling point at sea level and standard atmospheric pressure.

calibrate. To determine, by measurement or comparison with a standard, the correct value of each scale reading on a meter or other

device, or the correct value for each setting of a control knob.1

Carbon-Glass™. A temperature sensing material fabricated from a carbon-impregnated glass matrix used to make the Lake Shore

Carbon Glass Resistor (CGR) family of sensors.

Celsius (°C) Scale. A temperature scale that registers the freezing point of water as 0 °C and the boiling point as 100 °C under normal

atmospheric pressure. Celsius degrees are purely derived units, calculated from the Kelvin Thermodynamic Scale. Formerly known

as “centigrade.” See Temperature for conversions.

Cernox™. A Lake Shore resistance temperature detector based on a ceramic-oxy-nitride resistance material.

cgs system of units. A system in which the basic units are the centimeter, gram, and second.2

Chebychev polynomials. A family of orthogonal polynomials which solve Chebychev’s differential equation.1

Chebychev differential equation. A special case of Gauss' hypergeometric second-order differential equation:

(1 – x2) f" (x) – xf' (x) + n2f (x) = 0.1

closed-loop. See feedback control system.

coercive force (coercive field). The magnetic field strength (H) required to reduce the magnetic induction (B) in a magnetic material

to zero.

coercivity. generally used to designate the magnetic field strength (H) required to reduce the magnetic induction (B) in a magnetic

material to zero from saturation. The coercivity would be the upper limit to the coercive force.

cryotronics. The branch of electronics that deals with the design, construction, and use of cryogenic devices.1

Curie temperature (Tc). Temperature at which a magnetized sample is completely demagnetized due to thermal agitation. Named for

Pierre Curie (1859 – 1906), a French chemist.

current source. A type of power supply that supplies a constant current through a variable load resistance by automatically varying its

compliance voltage. A single specification given as “compliance voltage” means the output current is within specification when the

compliance voltage is between zero and the specified voltage.

curve. A set of data that defines the temperature response of a temperature sensor. It is used to convert the signal from the sensor to

temperature.

demagnetization. when a sample is exposed to an applied field (Ha), poles are induced on the surface of the sample. Some of the

returned flux from these poles is inside of the sample. This returned flux tends to decrease the net magnetic field strength internal to

the sample yielding a true internal field (Hint) given by: Hint = Ha – DM ,where M is the volume magnetization and D is the

demagnetization factor. D is dependent on the sample geometry and orientation with respect to the field.

deviation. The difference between the actual value of a controlled variable and the desired value corresponding to the setpoint.1

differential permeability. The slope of a B versus H curve: µd = dB/dH.

differential susceptibility. The slope of a M versus H curve: χd = dM/dH.

digital controller. A feedback control system where the feedback device (sensor) and control actuator (heater) are joined by a digital

processor. In Lake Shore controllers the heater output is maintained as a variable DC current source.

digital data. Pertaining to data in the form of digits or interval quantities. Contrast with analog data.2

dimensionless sensitivity. Sensitivity of a physical quantity to a stimulus, expressed in dimensionless terms. The dimensionless

temperature sensitivity of a resistance temperature sensor is expressed as Sd = (T/R)(dR/dT) which is also equal to the slope of R

versus T on a log-log plot, that is Sd = d lnR/d lnT. Note that the absolute temperature (in Kelvin) must be used in these expressions.

drift, instrument. An undesired but relatively slow change in output over a period of time, with a fixed reference input. Note: Drift is

usually expressed in percent of the maximum rated value of the variable being measured.2

electromagnet. A device in which a magnetic field is generated as the result of electrical current passing through a helical conducting

coil. It can be configured as an iron-free solenoid in which the field is produced along the axis of the coil, or an iron-cored structure

in which the field is produced in an air gap between pole faces. The coil can be water cooled copper or aluminum, or

superconductive.

electrostatic discharge (ESD). A transfer of electrostatic charge between bodies at different electrostatic potentials caused by direct

contact or induced by an electrostatic field.

error. Any discrepancy between a computed, observed, or measured quantity and the true, specified, or theoretically correct value or

condition.2

excitation. Either an AC or DC input to a sensor used to produce an output signal. Common excitations include: constant current,

constant voltage, or constant power.

Fahrenheit (°F) Scale. A temperature scale that registers the freezing point of water as 32 °F and the boiling point as 212 °F under

normal atmospheric pressure. See Temperature for conversions.

feedback control system. A system in which the value of some output quantity is controlled by feeding back the value of the

controlled quantity and using it to manipulate an input quantity so as to bring the value of the controlled quantity closer to a desired

value. Also known as closed-loop control system.1

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Glossary of Terminology A-3

four-lead. measurement technique where one pair of excitation leads and an independent pair of measurement leads are used to

measure a sensor. This method reduces the effect of lead resistance on the measurement.

gamma. A cgs unit of low-level flux density, where 100,000 gamma equals one oersted, or 1 gamma equals 10–5 oersted.

gauss (G). The cgs unit for magnetic flux density (B). 1 gauss = 10–4 tesla. Named for Karl Fredrich Gauss (1777 – 1855) a German

mathematician, astronomer, and physicist.

gaussian system (units). A system in which centimeter-gram-second units are used for electric and magnetic qualities.

general purpose interface bus (GPIB). Another term for the IEEE-488 bus.

germanium (Ge). A common temperature sensing material fabricated from doped germanium to make the Lake Shore GR family of

resistance temperature sensor elements.

gilbert (Gb). A cgs electromagnetic unit of the magnetomotive force required to produce one maxwell of magnetic flux in a magnetic

circuit of unit reluctance. One gilbert is equal to 10/4π ampere-turn. Named for William Gilbert

(1540 – 1603), an English physicist; hypothesized that the Earth is a magnet.

gilbert per centimeter. Practical cgs unit of magnet intensity. Gilberts per cm are the same as oersteds.

Greek alphabet. The Greek alphabet is defined as follows:

Alpha α Α Iota ι Ι Rho ρ Ρ

Beta β Β Kappa κ Κ Sigma σ Σ

Gamma γ Γ Lambda λ Λ Tau τ Τ

Delta δ Δ Mu μ Μ Upsilon υ Υ

Epsilon ε Ε Nu ν Ν Phi φ Φ

Zeta ζ Ζ Xi ξ Ξ Chi χ Χ

Eta η Η Omicron ο Ο Psi ψ Ψ

Theta θ Θ Pi π Π Omega ω Ω

ground. A conducting connection, whether intentional or accidental, by which an electric circuit or equipment is connected to the

Earth, or to some conducting body of relatively large extent that serves in place of the Earth.

Note: It is used for establishing and maintaining the potential of the Earth (or of the conducting body) or approximately that

potential, on conductors connected to it, and for conducting ground current to and from the Earth (or of the conducting body).2

H. Symbol for magnetic field strength. See Magnetic Field Strength.

Hall effect. The generation of an electric potential perpendicular to both an electric current flowing along a thin conducting material

and an external magnetic field applied at right angles to the current. Named for Edwin H. Hall (1855 – 1938), an American physicist.

hertz (Hz). A unit of frequency equal to one cycle per second.

hysteresis. The dependence of the state of a system on its previous history, generally in the form of a lagging of a physical effect

behind its cause.1 Also see magnetic hysteresis.

IEC. International Electrotechnical Commission.

IEEE. Institute of Electrical and Electronics Engineers.

IEEE-488. An instrumentation bus with hardware and programming standards designed to simplify instrument interfacing. The

addressable, parallel bus specification is defined by the IEEE.

initial permeability. The permeability determined at H = 0 and B = 0.

initial susceptibility. The susceptibility determined at H = 0 and M = 0.

infrared (IR). For practical purposes any radiant energy within the wavelength range 770 to 106 nanometers is considered infrared

energy.2 The full range is usually divided into three sub-ranges: near IR, far IR, and sub-millimeter.

interchangeability. Ability to exchange one sensor or device with another of the same type without a significant change in output or

response.

international system of units (SI). A universal coherent system of units in which the following seven units are considered basic:

meter, kilogram, second, ampere, Kelvin, mole, and candela. The International System of Units, or Système International d'Unités

(SI), was promulgated in 1960 by the Eleventh General Conference on Weights and Measures. For definition, spelling, and

protocols, see Reference 3 for a short, convenient guide.

interpolation table. A table listing the output and sensitivity of a sensor at regular or defined points which may be different from the

points at which calibration data was taken.

intrinsic coercivity. The magnetic field strength (H) required to reduce the magnetization (M) or intrinsic induction in a magnetic

material to zero.

intrinsic induction. The contribution of the magnetic material (Bi) to the total magnetic induction (B).

Bi = B – µ0H (SI) Bi = B – H (cgs)

isolated (neutral system). A system that has no intentional connection to ground except through indicating, measuring, or protective

devices of very-high impedance.2

Kelvin (K). The unit of temperature on the Kelvin Scale. It is one of the base units of SI. The word “degree” and its symbol (°) are

omitted from this unit. See Temperature Scale for conversions.

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A-4 Glossary of Terminology

Kelvin Scale. The Kelvin Thermodynamic Temperature Scale is the basis for all international scales, including the

ITS-90. It is fixed at two points: the absolute zero of temperature (0 K), and the triple point of water (273.16 K), the equilibrium

temperature that pure water reaches in the presence of ice and its own vapor.

line regulation. The maximum steady-state amount that the output voltage or current changes as result of a specified change in input

line voltage (usually for a step change between 105 – 125 or 210 – 250 volts, unless otherwise specified).

line voltage. The RMS voltage of the primary power source to an instrument.

load regulation. A steady-state decrease of the value of the specified variable resulting from a specified increase in load, generally

from no-load to full-load unless otherwise specified.

lock-in amplifier. An amplifier that uses some form of automatic synchronization with an external reference signal to detect and

measure very weak electromagnetic radiation at radio or optical wavelengths in the presence of very high noise levels.1

M. Symbol for magnetization. See magnetization.

magnetic air gap. The air space, or non-magnetic portion, of a magnetic circuit.

magnetic field strength (H). The magnetizing force generated by currents and magnetic poles. For most applications, the magnetic

field strength can be thought of as the applied field generated, for example, by a Electromagnet. The magnetic field strength is not a

property of materials. Measure in SI units of A/m or cgs units of oersted.

magnetic flux density (B). Also referred to as magnetic induction. This is the net magnetic response of a medium to an applied field,

H. The relationship is given by the following equation: B = µ0(H + M) for SI, and B = H + 4πM for cgs, where H = magnetic field

strength, M = magnetization, and µ0 = permeability of free space = 4π × 10–7 H/m.

magnetic hysteresis. The property of a magnetic material where the magnetic induction (B) for a given magnetic field strength (H)

depends upon the past history of the samples magnetization.

magnetic induction (B). See magnetic flux density.

magnetic moment (m). This is the fundamental magnetic property measured with dc magnetic measurements systems such as a

vibrating sample magnetometer, extraction magnetometer, SQUID magnetometer, etc. The exact technical definition relates to the

torque exerted on a magnetized sample when placed in a magnetic field. Note that the moment is a total attribute of a sample and

alone does not necessarily supply sufficient information in understanding material properties. A small highly magnetic sample can

have exactly the same moment as a larger weakly magnetic sample (see Magnetization). Measured in SI units as A·m2 and in cgs

units as emu. 1 emu = 10–3 A·m2.

magnetic units. Units used in measuring magnetic quantities. Includes ampere-turn, gauss, gilbert, line of force, maxwell, oersted,

and unit magnetic pole.

magnetization (M). This is a material specific property defined as the magnetic moment (m) per unit volume (V). M = m/V.

Measured in SI units as A/m and in cgs units as emu/cm3. 1 emu/cm3 = 103 A/m. Since the mass of a sample is generally much

easier to determine than the volume, magnetization is often alternately expressed as a mass magnetization defined as the moment

per unit mass.

microcontroller. A microcomputer, microprocessor, or other equipment used for precise process control in data handling,

communication, and manufacturing.1

MKSA System of Units. A system in which the basic units are the meter, kilogram, and second, and the ampere is a derived unit

defined by assigning the magnitude 4π × 10–7 to the rationalized magnetic constant (sometimes called the permeability of space).

negative temperature coefficient (NTC). Refers to the sign of the temperature sensitivity. For example, the resistance of a NTC

sensor decreases with increasing temperature.

National Institute of Standards and Technology (NIST). Government agency located in Gaithersburg, Maryland and Boulder,

Colorado, that defines measurement standards in the United States.

noise (electrical). Unwanted electrical signals that produce undesirable effects in circuits of control systems in which they occur.2

normalized sensitivity. For resistors, signal sensitivity (dR/dT) is geometry dependent; i.e., dR/dT scales directly with R;

consequently, very often this sensitivity is normalized by dividing by the measured resistance to give a sensitivity, sT, in percent

change per Kelvin. sT = (100/R) (dR/dT) %K, where T is the temp. in Kelvin and R is the resistance in ohms.

normally closed (N.C.). A term used for switches and relay contacts. Provides a closed circuit when actuator is in the free

(unenergized) position.

normally open (N.O.). A term used for switches and relay contacts. Provides an open circuit when actuator is in the free

(unenergized) position.

oersted (Oe). The cgs unit for the magnetic field strength (H). 1 oersted = 10¾π ampere/meter ≈79.58 ampere/meter.

ohm (Ω). The SI unit of resistance (and of impedance). The ohm is the resistance of a conductor such that a constant current of one

ampere in it produces a voltage of one volt between its ends.2

open-loop. A control system in which the system outputs are controlled by system inputs only, and no account is taken of actual

system output.1

pascal (Pa). The SI unit of pressure equal to 1 N/m2. Equal to 1.45 × 10–4 psi, 1.0197 × 10–5 kgf /cm2, 7.5 × 10–3 torr,

4.191 × 10–3 inches of water, or 1 × 10–5 bar.

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Glossary of Terminology A-5

permeability. Material parameter which is the ratio of the magnetic induction (B) to the magnetic field strength (H):

µ = B/H. Also see Initial Permeability and Differential Permeability.

platinum (Pt). A common temperature sensing material fabricated from pure platinum to make the Lake Shore PT family of

resistance temperature sensor elements.

polynomial fit. A mathematical equation used to fit calibration data. Polynomials are constructed of finite sums of terms of the form

aixi , where ai is the ith fit coefficient and xi is some function of the dependent variable.

positive temperature coefficient (PTC). Refers to the sign of the temperature sensitivity. For example, the resistance of a PTC sensor

increases with increasing temperature.

pounds per square inch (psi). A unit of pressure. 1 psi = 6.89473 kPa. Variations include psi absolute (psia) measured relative to

vacuum (zero pressure) where one atmosphere pressure equals 14.696 psia and psi gauge (psig) where gauge measured relative to

atmospheric or some other reference pressure.

ppm. Parts per million, e.g., 4 × 10–6 is four parts per million.

precision. Careful measurement under controlled conditions which can be repeated with similar results. See repeatability. Also means

that small differences can be detected and measured with confidence. See resolution.

prefixes. SI prefixes used throughout this manual are as follows:

Factor Prefix Symbol

1024 yotta Y

1021 zetta Z

1018 exa E

1015 peta P

1012 tera T

109 giga G

106 mega M

103 kilo k

102 hecto h

101 deka da

Factor Prefix Symbol

10–1 deci d

10–2 centi c

10–3 milli m

10–6 micro µ

10–9 nano n

10–12 pico p

10–15 femto f

10–18 atto a

10–21 zepto z

10–24 yocto y

probe. A long, thin body containing a sensing element which can be inserted into a system in order to make measurements. Typically,

the measurement is localized to the region near the tip of the probe.

proportional, integral, derivative (PID). A control function where output is related to the error signal in three ways. Proportional

(gain) acts on the instantaneous error as a multiplier. Integral (reset) acts on the area of error with respect to time and can eliminate

control offset or droop. Derivative (rate) acts on the rate of change in error to dampen the system, reducing overshoot.

rack mount. An instrument is rack mountable when it has permanent or detachable brackets that allow it to be securely mounted in an

instrument rack. The standard rack-mount is 19 inches wide. A full-rack instrument requires the entire width of the rack. Two half-

rack instruments fit horizontally in one rack width.

relief valve. A type of pressure relief device which is designed to relieve excessive pressure, and to reclose and reseal to prevent

further flow of gas from the cylinder after reseating pressure has been achieved.

remanence. The remaining magnetic induction in a magnetic material when the material is first saturated and then the applied field is

reduced to zero. The remanence would be the upper limit to values for the remanent induction. Note that no strict convention exists

for the use of remanent induction and remanence and in some contexts the two terms may be used interchangeably.

remanent induction. The remaining magnetic induction in a magnetic material after an applied field is reduced to zero. Also see

remanence.

repeatability. The closeness of agreement among repeated measurements of the same variable under the same conditions.2

resistance temperature detector (RTD). Resistive sensors whose electrical resistance is a known function of the temperature, made

of, e.g., carbon-glass, germanium, platinum, or rhodium-iron.

resolution. The degree to which nearly equal values of a quantity can be discriminated.2

display resolution. The resolution of the physical display of an instrument. This is not always the same as the measurement

resolution of the instrument. Decimal display resolution specified as "n digits" has 10n possible display values. A resolution of n

and one-half digits has 2 × 10n possible values.

measurement resolution. The ability of an instrument to resolve a measured quantity. For digital instrumentation this is often

defined by the analog to digital converter being used. A n-bit converter can resolve one part in 2n. The smallest signal change that

can be measured is the full scale input divided by 2n for any given range. Resolution should not be confused with accuracy.

RhFe. Rhodium-iron. Rhodium alloyed with less than one atomic percent iron is used to make the Lake Shore RF family of sensors.

Rhodium-iron is a spin fluctuation alloy which has a significant temperature coefficient of resistance below 20 K where most metals

rapidly lose sensitivity.

root mean square (RMS). The square root of the time average of the square of a quantity; for a periodic quantity the average is taken

over one complete cycle. Also known as effective value.1

RS-232C. Bi-directional computer serial interface standard defined by the Electronic Industries Association (EIA). The interface is

single-ended and non-addressable.

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A-6 Glossary of Terminology

Seebeck effect. The development of a voltage due to differences in temperature between two junctions of dissimilar metals in the

same circuit.1

self-heating. Heating of a device due to dissipation of power resulting from the excitation applied to the device. The output signal

from a sensor increases with excitation level, but so does the self-heating and the associated temperature measurement error.

sensitivity. The ratio of the response or change induced in the output to a stimulus or change in the input. Temperature sensitivity of a

resistance temperature detector is expressed as S = dR/dT.

setpoint. The value selected to be maintained by an automatic controller.1

serial interface. A computer interface where information is transferred one bit at a time rather than one byte (character) at a time as in

a parallel interface. RS-232C is the most common serial interface.

SI. Système International d'Unités. See International System of Units.

stability. The ability of an instrument or sensor to maintain a constant output given a constant input.

strain relief. A predetermined amount of slack to relieve tension in component or lead wires. Also called stress relief.

susceptance. In electrical terms, susceptance is defined as the reciprocal of reactance and the imaginary part of the complex

representation of admittance: [suscept(ibility) + (conduct)ance].

susceptibility (χ). Parameter giving an indication of the response of a material to an applied magnetic field. The susceptibility is the

ratio of the magnetization (M) to the applied field (H). χ = M/H. In both SI units and cgs units the volume susceptibility is a

dimensionless parameter. Multiply the cgs susceptibility by 4π to yield the SI susceptibility. See also Initial Susceptibility and

Differential Susceptibility. As in the case of magnetization, the susceptibility is often seen expressed as a mass susceptibility or a

molar susceptibility depending upon how M is expressed.

temperature scales. See Kelvin Scale, Celsius Scale, and ITS-90. Proper metric usage requires that only Kelvin and degrees Celsius

be used. However, since degrees Fahrenheit is in such common use, all three scales are delineated as follows:

Boiling point of water

Freezing point of water

Absolute zero kelvin Celsius Fahrenheit

0 K

273.15 K

373.15 K

–273.15 °C

0 °C

100 °C

–

459.67 °F

32 °F

212 °F

Triple point of water 273.16 K

To convert Kelvin to Celsius, subtract 273.15.

To convert Celsius to Fahrenheit: multiply °C by 1.8 then add 32, or: °F = (1.8 × °C) + 32.

To convert Fahrenheit to Celsius: subtract 32 from °F then divide by 1.8, or: °C = (°F – 32 )/1.8.

temperature coefficient, measurement. The measurement accuracy of an instrument is affected by changes in ambient temperature.

The error is specified as an amount of change (usually in percent) for every one degree change in ambient temperature.

tesla (T). The SI unit for magnetic flux density (B). 1 tesla = 104 gauss

thermal emf. An electromotive force arising from a difference in temperature at two points along a circuit, as in the Seebeck effect.1

tolerance. The range between allowable maximum and minimum values.

torr. Unit of pressure. 1 torr ≈ 1 mm of mercury. 1 atmosphere = 760 torr.

two-lead. Measurement technique where one pair of leads is used for both excitation and measurement of a sensor. This method will

not reduce the effect of lead resistance on the measurement.

Underwriters Laboratories (UL). An independent laboratory that establishes standards for commercial and industrial products.

unit magnetic pole. A pole with a strength such that when it is placed 1 cm away from a like pole, the force between the two is 1

dyne.

volt (V). The difference of electric potential between two points of a conductor carrying a constant current of one ampere, when the

power dissipated between these points is equal to one watt.2

volt-ampere (VA). The SI unit of apparent power. The volt-ampere is the apparent power at the points of entry of a single-phase, two-

wire system when the product of the RMS value in amperes of the current by the RMS value in volts of the voltage is equal to one.2

watt (W). The SI unit of power. The watt is the power required to do work at the rate of 1 joule per second.2

References:

1 Sybil P. Parker, Editor. McGraw-Hill Dictionary of Scientific and Technical Terms: Fifth Edition.

New York: McGraw Hill, 1994 (IBSN 0-07-113584-7)

2 Christopher J. Booth, Editor. The New IEEE Standard Dictionary of Electrical and Electronic Terms:

IEEE Std 100-1992, Fifth Edition. New York: Institute of Electrical and Electronics Engineers, 1993

(IBSN 1-55937-240-0)

3 Nelson, Robert A. Guide For Metric Practice, Page BG7 - 8, Physics Today, Eleventh Annual Buyer’s Guide,

August 1994 (ISSN 0031-9228 coden PHTOAD)

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

Units for Magnetic Properties B-1

APPENDIX B

UNITS FOR MAGNETIC PROPERTIES

Table B-1. Conversion from CGS to SI Units

Quantity Symbol Gaussian

& CGS emua Conversion

Factor, Cb SI &

Rationalized mksc

Magnetic flux density,

Magnetic induction B gauss (G)d 10-4 tesla (T), Wb/m2

Magnetic Flux φ maxwell (Mx), G•cm2 10-8 weber (Wb), volt

second (V•s)

Magnetic potential difference,

magnetomotive force U, F gilbert (Gb) 10/4π ampere (A)

Magnetic field strength,

magnetizing force H oersted (Oe),e Gb/cm 103/4π A/mf

(Volume) magnetizationg M emu/cm3h 103 A/m

(Volume) magnetization 4πM G 103/4π A/m

Magnetic polarization,

intensity of magnetization J, I emu/cm3 4π × 10-4 T, Wb/m2i

(Mass) magnetization σ, M emu/g 1

4π × 10-7

A•m2/kg

Wb•m/kg

Magnetic moment m emu, erg/G 10-3 A•m2, joule per tesla

(J/T)

Magnetic dipole moment j emu, erg/G

4π × 10-10 Wb•mi

(Volume) susceptibility χ, κ dimensionless

emu/cm3

—

(4π)2 × 10-7

Henry per meter

(H/m), Wb/(A•m)

(Mass) susceptibility χρ, κρ cm3/g, emu/g 4π × 10-3

(4π)2 × 10-10

m3/kg

H•m2/kg

(Molar) susceptibility χmol, κmol cm3/mol, emu/mol 4π × 10-6

(4π)2 × 10-13

m3/mol

H•m2/mol

Permeability µ dimensionless

4π × 10-7 H/m, Wb/(A•m)

Relative permeabilityj µr not defined — dimensionless

(Volume) energy density,

energy productk W erg/cm3 10-1 J/m3

Demagnetization factor D, N dimensionless 1/4π dimensionless

NOTES:

a. Gaussian units and cgs emu are the same for magnetic properties. The defining relation is B = H + 4πM.

b. Multiply a number in Gaussian units by C to convert it to SI (e.g. 1 G × 10-4T/G = 10-4T).

c. SI (Système International d'Unités) has been adopted by the National Bureau of Standards. Where two conversion factors are given, the upper one is

recognized under, or consistent with, SI and is based on the definition B = µ0(H + M), where to µ0 = 4π × 10-7H/m. The lower one is not recognized under SI

and is based on the definition B = µ0H + J, where the symbol I is often used in place of J.

d. 1 gauss = 105 gamma (γ).

e. Both oersted and gauss are expressed as cm-½ •g½•s-1 in terms of base units.

f. A/m was often expressed as "ampere-turn per meter" when used for magnetic field strength.

g. Magnetic moment per unit volume.

h. The designation "emu" is not a unit.

i. Recognized under SI, even though based on the definition B = µ0H + J. See footnote c.

j. µr = µ/µ0 = 1 + χ, all in SI. µr is equal to Gaussian µ.

k. B • H and µ0M • H have SI units J/m3, M • H and B • H/4π have Gaussian units erg/cm3.

R.B. Goldfarb and F.R. Fickett, U.S. Department of Commerce, National Bureau of Standards, Bolder, Colorado 80303, March 1985, NBS Special Publication

696. For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

Lake Shore Model 642 Electromagnet Power Supply User’s Manual

B-2 Units for Magnetic Properties

Table B-2. Recommended SI Values for Physical Constants

Quantity Symbol Value (SI units)

Permeability of Vacuum µ0 4π × 10-7 H m-1

Speed of Light in Vacuum c 2.9979 × 108 m s-1

Permitivity of Vacuum ε0 = (µ0c2)-1 8.8542 × 10-12 F m-1

Fine Structure Constant, µ0ce2/2h α

α-1

0.0073

137.0360

Elementary Charge e 1.6022 × 10-19 C

Plank's Constant h

h = h/2π

6.6262 × 10-34 J Hz-1

1.0546 × 10-34 J s

Avogadro's Constant NA 6.0220 × 1023 mol-1

Atomic Mass Unit 1 u = 10-3 kg mol-1/NA 1.6605 × 10-27 kg

Electron Rest Mass me 0.9109 × 10-30 kg

5.4858 × 10-4 u

Proton Rest Mass mp 1.6726 × 10-27 kg

1.0073 u

Neutron Rest Mass mn 1.6749 × 10-27 kg

1.0087 u

Magnetic Flux Quantum φ = h/2e

h/e

2.0679 × 10-15 Wb

4.1357 × 10-15 J Hz-1 C-1

Josephson Frequency-Voltage Ratio 2e/h 483.5939 THz V-1

Quantum of Circulation h/2me

h/me

3.6369 × 10-4 J Hz-1 kg-1

7.2739 × 10-4 J Hz-1 C-1

Rydberg Constant R∞ 1.0974 × 107 m-1

Proton Moment in Nuclear Magnetons µp/µN 2.7928

Bohr Magneton µB = eh/2me 9.2741 × 10-24 J T-1

Proton Gyromagnetic Ratio γp 2.6752 × 108 s-1 T-1

Diamagnetic Shielding Factor, Spherical H2O Sample 1 + σ(H2O) 1.0000

Molar Mass Constant R 8.3144 J mol-1 K-1

Molar Volume, Ideal Gas (T0 = 273.15K, p0 = 1 atm) Vm = RT0/p0 0,0224 m3 mol-1

Boltzman Constant k = R/NA 1.3807 × 10-23 J K-1

Stefan-Boltzman Constant σ = (π2/60) k4/h3 c2 5.6703 × 10-8 W m-2 K-4

First Radiation Constant c1= 2πhc2 3.7418 × 10-16 W m-2

Second Radiation Constant c2 = hc/k 0.0144 mK

Gravitation Constant G 6.6720 × 10-11 N m2 kg-2

Data (abbreviated to 4 decimal places) from CODATA Bulletin No. 11, ICSU CODATA Central Office, 19 Westendstrasse,

6 Frankfurt/Main, Germany. Copies of this bulletin are available from this office.

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