Fluke 1521 Users Manual

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2015-02-02

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Hart Scientific

1521
Handheld Thermometer Readout
User’s Guide

Rev. 571203 ENG

Limited Warranty & Limitation of Liability
Each product from Fluke's Hart Scientific Division ("Hart") is warranted to be free from defects in material and workmanship under normal use and service. The warranty period is one year for the Handheld
Thermometer Readout. The warranty period begins on the date of the shipment. Parts, product repairs,
and services are warranted for 90 days. The warranty extends only to the original buyer or end-user customer of a Hart authorized reseller, and does not apply to fuses, disposable batteries or to any other product which, in Hart's opinion, has been misused, altered, neglected, or damaged by accident or abnormal
conditions of operation or handling. Hart warrants that software will operate substantially in accordance
with its functional specifications for 90 days and that it has been properly recorded on non-defective media. Hart does not warrant that software will be error free or operate without interruption. Hart does not
warrant calibrations on Handheld Thermometer Readouts.
Hart authorized resellers shall extend this warranty on new and unused products to end-user customers
only but have no authority to extend a greater or different warranty on behalf of Hart. Warranty support is
available if product is purchased through a Hart authorized sales outlet or Buyer has paid the applicable
international price. Hart reserves the right to invoice Buyer for importation costs of repairs/replacement
parts when product purchased in one country is submitted for repair in another country.
Hart's warranty obligation is limited, at Hart's option, to refund of the purchase price, free of charge repair, or replacement of a defective product which is returned to a Hart authorized service center within
the warranty period.
To obtain warranty service, contact your nearest Hart authorized service center or send the product, with
a description of the difficulty, postage, and insurance prepaid (FOB Destination), to the nearest Hart authorized service center. Hart assumes no risk for damage in transit. Following warranty repair, the product will be returned to Buyer, transportation prepaid (FOB Destination). If Hart determines that the
failure was caused by misuse, alteration, accident or abnormal condition or operation or handling, Hart
will provide an estimate or repair costs and obtain authorization before commencing the work. Following
repair, the product will be returned to the Buyer transportation prepaid and the Buyer will be billed for
the repair and return transportation charges (FOB Shipping Point).
THIS WARRANTY IS BUYER'S SOLE AND EXCULSIVE REMEDY AND IS IN LIEU OF ALL
OTHER WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTY OF MERCHANTABLILTY OR FITNESS FOR A PARTICULAR PURPOSE.
HART SHALL NOT BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL. OR CONSEQUENTIAL DAMAGES OR LOSSES, INCLUDING LOSS OF DATA, WHETHER ARISING FROM
BREACH OF WARRANTY OR BASED ON CONTRACT, TORT, RELIANCE OR ANY OTHER
THEORY.
Since some countries or states do not allow limitation of the term of an implied warranty, or exclusion or
limitation of incidental or consequential damages, the limitations and exclusions of this warranty may not
apply to every buyer. If any provision of this Warranty is held invalid or unenforceable by a court of competent jurisdiction, such holding will not affect the validity or enforceability of any other provision.
Fluke Corporation, Hart Scientific Division
799 E. Utah Valley Drive American Fork, UT 84003-9775 USA
Phone: +1.801.763.1600 Telefax: +1.801.763.1010
E-mail: support@hartscientific.com
www.hartscientific.com
Subject to change without notice. Copyright © 2005 Printed in USA

Rev. 571203

Table of Contents
1 Before You Start . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1
1.2

Symbols Used . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Safety Information . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.1
1.2.2

1.3

Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Cautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Authorized Service Centers. . . . . . . . . . . . . . . . . . . . . . 4

2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3 Specifications and Environmental Conditions . . . . . . . . . . 9
3.1
3.2

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Environmental Conditions. . . . . . . . . . . . . . . . . . . . . . 10

4 Quick Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1
4.2

Unpacking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Use Proper Care with the 1521 and Accessories . . . . . . . . . . 11

4.3
4.4
4.5

Learn About the Features and Components . . . . . . . . . . . . . 11
Connect the Probe . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Connect the Power Source . . . . . . . . . . . . . . . . . . . . . 12

4.6
4.7

Switch the Power On . . . . . . . . . . . . . . . . . . . . . . . . 12
Measure Temperature . . . . . . . . . . . . . . . . . . . . . . . . 12

5 Parts and Controls . . . . . . . . . . . . . . . . . . . . . . . . 13
5.1
5.2
5.3

Front Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Top and Side Features . . . . . . . . . . . . . . . . . . . . . . . . 15
Back Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

5.4
5.5

Internal Features. . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6 General Operation . . . . . . . . . . . . . . . . . . . . . . . . 19
6.1
6.2
6.3
6.4
6.5

Battery . . . . . . . . .
DC Power Source . . .
Power Button . . . . .
Display and Backlight .
Probe . . . . . . . . .

.
.
.
.
.

19
20
21
21
22

6.6

INFO-CON Connector . . . . . . . . . . . . . . . . . . . . . . . 23

7 Display Functions. . . . . . . . . . . . . . . . . . . . . . . . . 25
7.1

Blank Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

7.2
7.3

Min/Max Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Hold Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

7.4
7.5

Delta(x) Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

7.6
7.7

Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

7.8

CAL MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
7.8.1
7.8.2
7.8.3
7.8.4
7.8.5
7.8.6
7.8.7
7.8.8
7.8.9
7.8.10
7.8.11
7.8.12
7.8.13
7.8.14
7.8.15
7.8.16
7.8.17
7.8.18
7.8.19
7.8.20

Mtr Due . . . . .
Prb Due . . . . .
Time . . . . . . .
Passcode. . . . .
Date . . . . . . .
Probe Lock . . .
Prb #. . . . . . .
Prb Type . . . . .
ITS-90 . . . . . .
IEC751 . . . . .
CVD . . . . . . .
YSI-400 . . . . .
THERM . . . .
Probe Wires . . .
PCal . . . . . . .
PDue . . . . . .
Filter. . . . . . .
MCal . . . . . .
MDue . . . . . .
CAL1 and CAL2

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

. 30
. 30
. 30
. 30
. 31
. 31
. 31
. 31
. 32
. 33
. 33
. 34
. 34
. 35
. 35
. 35
. 36
. 36
. 36
. 36

8 Communications Interface. . . . . . . . . . . . . . . . . . . . 37
8.1
8.2

RS-232 Connection . . . . . . . . . . . . . . . . . . . . . . . . . 37
Communication Command List . . . . . . . . . . . . . . . . . . . 38
8.2.1
8.2.2

Primary Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Calibration Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

9 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
9.1
9.2

Required Equipment. . . . . . . . . . . . . . . . . . . . . . . . . 43
Calibration Procedure . . . . . . . . . . . . . . . . . . . . . . . . 43

10 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

11 Troubleshooting. . . . . . . . . . . . . . . . . . . . . . . . . . 47
11.1
11.2

An Error Message Is Displayed . . . . . . . . . . . . . . . . . . . 47
CE Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
11.2.1

EMC Directive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

11.2.1.1
11.2.1.2

11.2.2

Immunity Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Emission Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Low Voltage Directive (Safety) . . . . . . . . . . . . . . . . . . . . . . . . . 49

iii

Figures and Tables
Table 1
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8

International Electrical Symbols . . . . . . . . . . . . . . . . . . . . . 1
Front of the 1521 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Top and Side View . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
INFO-CON Connector . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Battery Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
12V DC Power Source Polarity . . . . . . . . . . . . . . . . . . . . . 21
Probe Wiring Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . 24
Operating Modes Flowchart . . . . . . . . . . . . . . . . . . . . . . . 26
RS-232 Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

1 Before You Start
Symbols Used

1
1.1

Before You Start
Symbols Used
Table 1 lists the International Electrical Symbols. Some or all of these symbols
may be used on the instrument or in this manual.
Table 1 International Electrical Symbols
Symbol

Description
AC (Alternating Current)

AC-DC

Battery

CE Complies with European Union Directives

Double Insulated

Electric Shock

Fuse

PE Ground

Hot Surface (Burn Hazard)

Read the User’s Manual (Important Information)

Off

1521 Handheld Thermometer Readout
User’s Guide

Symbol

Description
Canadian Standards Association

OVERVOLTAGE (Installation) CATEGORY II, Pollution Degree 2 per IEC1010-1 refers to the level of Impulse Withstand Voltage protection provided. Equipment of
OVERVOLTAGE CATEGORY II is energy-consuming equipment to be supplied from
the fixed installation. Examples include household, office, and laboratory appliances.
C-TIC Australian EMC Mark

The European Waste Electrical and Electronic Equipment (WEEE) Directive
(2002/96/EC) mark.

1.2

Safety Information
Use this instrument only as specified in this manual. Otherwise, the protection
provided by the instrument may be impaired.
The following definitions apply to the terms “Warning” and “Caution”.
• “Warning” identifies conditions and actions that may pose hazards to the
user.
• “Caution” identifies conditions and actions that may damage the instrument being used.

1.2.1

Warnings
To avoid personal injury, follow these guidelines.
• DO NOT use this unit in environments other than those listed in the
User’s Guide.
• Follow all safety guidelines listed in the User’s Guide.
• Calibration equipment should only be used by trained personnel.
• If this equipment is used in a manner not specified by the manufacturer,
the protection provided by the equipment may be impaired.
• Before initial use, or after transport, or after storage in humid or semi-humid environments, or anytime the instrument has not been energized for
more than 10 days, the instrument needs to be energized for a "dry-out"
period of 2 hours before it can be assumed to meet all of the safety requirements of the IEC 1010-1. If the product is wet or has been in a wet
environment, take necessary measures to remove moisture prior to applying power such as storage in a low humidity temperature chamber
operating at 50°C for 4 hours or more.
• This instrument can measure extreme temperatures. Precautions must be
taken to prevent personal injury or damage to objects. Probes may be extremely hot or cold. Cautiously handle probes to prevent personal injury.

1 Before You Start
Safety Information

Carefully place probes on a heat/cold resistant surface or rack until they
reach room temperature.
• The AC adapter can present safety concerns if misused or damaged. To
avoid the risk of electric shock or fire, do not use the AC adapter outdoors
or in a dusty, dirty, or wet environment. If the cord, case, or plug of the
adapter is damaged in any way, discontinue its use immediately and have
it replaced. Never disassemble the AC adapter. Use only the AC adapter
provided with the instrument or equivalent adapter recommended by the
manufacturer of this instrument.
• The AC adapter has circuits with high voltage inside that could present
danger of electrical shock or fire if exposed. If the AC adapter is damaged
in any way or becomes hot, discontinue its use immediately, disconnect it
from any AC supply, and have it replaced. Do not attempt to open, repair,
or continue using a damaged or defective AC adapter.
• The instrument batteries can present danger if not handled properly. To
avoid the risk of exposure to dangerous substances or explosion, immediately remove the batteries and discontinue use if they leak or become
damaged. Never allow the batteries to be shorted, heated, punctured, or
dropped. If the instrument is physically damaged, immediately remove
the batteries to insure that they do not become shorted. While removed
from the instrument, store the batteries in a location so that they do not
come into contact with metal or fluids that might short circuit the batteries
and where they are safe from excessive temperatures. Used batteries must
be disposed of properly. Check your local regulations for additional information. You may return the used batteries to the manufacturer. Never dispose of batteries in fire which may result in explosion with the possibility
of personal injury or property damage.
• DO NOT use this instrument in combination with any probe (RTD or
thermistor) to measure the temperature or resistance of any device that is
electrically energized. Severe electric shock, personal injury, or death may
occur.

1.2.2

Cautions
To avoid possible damage to the instrument, follow these guidelines.
• If the instrument is dropped, struck, or handled in a way that causes internal or external physical damage, immediately unplug the AC adapter, remove the batteries, discontinue use, and contact the factory for repair. Do
not attempt to disassemble or repair the instrument, batteries, or AC
adapter. Refer repairs or replacement components to the manufacturer.
• The instrument and thermometer probes are sensitive and can be easily
damaged. Always handle these devices with care. DO NOT allow them to
be dropped, struck, stressed, or overheated.
• DO NOT leave the AC adapter plugged in for more than 24 consecutive
hours or the battery life could be degraded.

1521 Handheld Thermometer Readout
User’s Guide

• Probes are fragile devices which can be damaged by mechanical shock,
overheating, and absorption of moisture or fluids in the wires or hub.
Damage may not be visibly apparent but nevertheless can cause drift, instability, and loss of accuracy. Observe the following precautions:
• DO NOT allow probes to be dropped, struck, bent, or stressed.
• DO NOT overheat probes beyond their recommended temperature range.
• DO NOT allow any part of the probe other than the sheath to be immersed in fluid.
• DO NOT allow the probe hub or wires to be exposed to excessive temperatures.
• Keep the probe wires clean and away from fluids.

1.3

Authorized Service Centers
Please contact one of the following authorized Service Centers to coordinate
service on your Hart product:
Fluke Corporaton, Hart Scientific Division
799 E. Utah Valley Drive
American Fork, UT 84003-9775
USA
Phone: +1.801.763.1600
Telefax: +1.801.763.1010
E-mail: support@hartscientific.com
Fluke Nederland B.V.
Customer Support Services
Science Park Eindhoven 5108
5692 EC Son
NETHERLANDS
Phone: +31-402-675300
Telefax: +31-402-675321
E-mail: ServiceDesk@fluke.nl
Fluke Int'l Corporation
Service Center - Instrimpex
Room 2301 Sciteck Tower
22 Jianguomenwai Dajie

1 Before You Start
Authorized Service Centers

Chao Yang District
Beijing 100004, PRC
CHINA
Phone: +86-10-6-512-3436
Telefax: +86-10-6-512-3437
E-mail: xingye.han@fluke.com.cn
Fluke South East Asia Pte Ltd.
Fluke ASEAN Regional Office
Service Center
60 Alexandra Terrace #03-16
The Comtech (Lobby D)
118502
SINGAPORE
Phone: +65 6799-5588
Telefax: +65 6799-5588
E-mail: antng@singa.fluke.com
When contacting these Service Centers for support, please have the following
information available:
• Model Number
• Serial Number
• Voltage
• Complete description of the problem

2 Introduction

Introduction
The 1521 Handheld Thermometer Readout is a low-cost, high-accuracy digital
thermometer readout designed to be used with PRTs and thermistors. The
unique combination of features makes this instrument suitable for a wide variety of applications in industry. Features and capabilities of the 1521 include the
following:
• Measures with platinum resistance thermometers (PRTs) and thermistors
• Works with Hart’s special INFO-CON probe connector (which is partially
based on U.S. Patent 5,857,777) to automatically recognize the type of
sensor and its characteristics
• Automatically alerts the operator when the probe calibration or meter calibration expires
• Measures with an accuracy of ±0.025°C at 25°C with PRTs and ±0.005°C
at 25°C with thermistors
• Accepts three- or four-wire sensors to eliminate lead resistance errors
• Is immune to thermoelectric EMF
• Measures with a fast one-second measurement cycle
• Displays maximum, minimum, and delta temperatures
• Stores up to six measurements in memory
• Uses a unique factory-assigned pass-code to protect programmed settings
• Displays measurements and settings on a high-contrast LCD display
• Communicates with other equipment using an RS-232 serial interface
• Can be powered from its AC adapter or rechargeable battery

3 Specifications and Environmental Conditions
Specifications

3
3.1

Specifications and Environmental
Conditions
Specifications
Resistance Range

0Ω to 500 kΩ

Resistance Accuracy, PRT, one
year†

0Ω to 25Ω: 0.002Ω
25Ω to 400Ω: 0.008% (80 ppm) of reading

Resistance Accuracy, thermistor,
one year†

0Ωto 2 kΩ: 0.4Ω
2 kΩ to 200 kΩ: 0.02% (200 ppm) of reading
200 kΩ to 500 kΩ: 0.03% (300 ppm) of reading

Temperature Range

PRT: –200°C to 962°C (–328°F to 1764°F)
Thermistor: –50°C to 150°C (–58°F to 302°F)

Temperature Accuracy, PRT†

–200°C to 100°C: ±0.025°C (0.045°F)
100°C to 400°C: ±0.05°C (0.09°F)
400°C to 800°C: ±0.1°C (0.18°F)
800°C to 962°C: ±0.15°C (0.27°F)

Temperature Accuracy,
2.25 kΩ thermistor†

–50 to 25°C: ±0.005°C (0.009°F)
25°C to 50°C: ±0.01°C (0.018°F)
50°C to 75°C: ±0.03°C (0.054°F)
75°C to 100°C: ±0.08°C (0.144°F)

Temperature Accuracy,
10 kΩ thermistor†

0 to 50°C: ±0.005°C (0.009°F)
50°C to 75°C: ±0.01°C (0.018°F)
75°C to 100°C: ±0.02°C (0.036°F)
100°C to 125°C: ±0.05°C (0.09°F)
125°C to 150°C: ±0.1°C (0.18°F)

Temperature Accuracy,
100 kΩ thermistor†

0 to 50°C: 0.006°C (0.011°F)
50°C to 150°C: 0.009°C (0.016°F)

Resistance Resolution

0.001Ω

Temperature Resolution

0.001°C, F, K, R

Probe

IEC-751 or DIN-43760 PRT
Callendar-Van Dusen calibrated PRT; nominal 100Ω
ITS-90 calibrated 25Ω or 100Ω PRT
YSI-400 series or equivalent 2252Ω thermistor
Steinhart-Hart thermistor polynomial; nominal R(25°C) 2kΩ to
100kΩ

Probe Connector

Hart Scientific INFO-CON connector

Maximum Acceptable Probe Lead
Resistance

10Ω

Probe Excitation Current

PRT: 0.5 mA
Thermistor: 5 μA

Measurement Period

1 second

1521 Handheld Thermometer Readout
User’s Guide

Digital Filter

Exponential with adjustable time constant (1 to 60 seconds)

Remote Communications

RS-232 serial

Display

LCD, 6-digit x 7-segment with 16-character alphanumeric

Operating Temperature Range

0 to 40°C (32 to 104°F) absolute
15 to 35°C (59 to 95°F) full accuracy

Power

12 VDC (AC adapter included)
Rechargeable NiMH batteries (included)

Safety

OVERVOLTAGE (Installation) CATEGORY II, Pollution Degree 2 per
IEC1010-1 refers to the level of Impulse Withstand Voltage protection provided. Equipment of OVERVOLTAGE CATEGORY II is energy-consuming equipment to be supplied from the fixed installation.
Examples include household, office, and laboratory appliances.

Size

7.75"H x4.2"Wx1.5"D (20 cm H x 11 cm W x 4 cm D)

Weight

0.4 kg (1.0 lb.)

†Accuracy

specifications apply from 15 to 35°C. Accuracy specifications over the entire absolute operating
range are 1.5 times the stated values. Temperature accuracy does not include probe uncertainty or probe
characterization errors. The practical measurement range may be limited by the sensor.

3.2

Environmental Conditions
Although the instrument has been designed for optimum durability and trouble-free operation, it must be handled with care. The instrument should not be
operated in an excessively dusty, dirty, or wet environment. Maintenance and
cleaning recommendations can be found in the Maintenance section of this
manual.
For full accuracy, operate the instrument in ambient temperatures between
15-35°C (59-95°F). Do not operate the instrument in an environment colder
than 5°C (41°F) or warmer than 50°C (122°F).
The instrument operates safely under the following conditions:
• Operating temperature range: absolute 5–50°C (41–122°F);
full accuracy15-35°C (59-95°F)
• ambient relative humidity: maximum 80% for temperature <31°C, decreasing linearly to 50% at 40°C
• Pressure: 75kPa-106kPa
• Vibration should be minimized
• Altitude less than 2,000 meters
• Indoor use only

4 Quick Start
Unpacking

Quick Start
This section briefly explains the basics of setting up and operating your 1521
Thermometer.

4.1

Unpacking
Carefully unpack the 1521 and accessories and inspect them to make sure all
components are present and in satisfactory condition. Verify that the following
items are present:
• 1521 Thermometer
• AC Adapter (clamp-on ferrite installed)
• Serial Cable
• User’s Guide
• Report of Calibration
• Calibration Label
• Pass-code Notice
• INFO-CON Connector
• Clamp-on ferrite with instructions for probe
• Probe (optional—must be purchased separately)
If all items are not present, call an Authorized Service Center (see Section 1.3).

4.2

Use Proper Care with the 1521 and Accessories
First and most important is to understand the safety issues related to the 1521
and its accessories. Be aware that potential hazards exist due to high temperatures, high voltages, and battery chemicals. Carefully read Section .
CAUTION: The 1521 and any thermometer probes are sensitive instruments that can be easily damaged. Always handle these devices with care.
DO NOT allow them to be dropped, struck, stressed, or overheated.

4.3

Learn About the Features and Components
Familiarize yourself with the features and accessories of the 1521 by reading
Section 5.

4.4

Connect the Probe
The PRT or thermistor probe connects to the top of the 1521 using Hart’s
unique INFO-CON probe connector. The probe connector is inserted into the
11

1521 Handheld Thermometer Readout
User’s Guide

top of the instrument with the ridged side down. It will fit snugly and lock into
place when it is fully inserted.
The INFO-CON probe connector includes a memory device that stores the
unique characteristics of the probe, allowing the 1521 to measure temperature accurately. If your probe was purchased from Hart for use with the 1521 it
should already have the connector attached and properly programmed. You can
use your own probe with the 1521, but you must attach it with an INFO-CON
connector. See Section 6.6 for more information on the INFO-CON connector.

4.5

Connect the Power Source
The 1521 draws power from either a DC power supply (the included AC
adapter) connected to the DC input or the internal rechargeable battery pack. To
use the AC adapter, plug it into a wall outlet of the appropriate voltage and insert the DC plug into the DC power input of the 1521 (see Figure 2.) To use the
battery pack it must first be fully charged using the AC adapter (see Section
6.1).

4.6

Switch the Power On
Power is switched on and off with the power button located below and to the
left of the display. To switch the power on, hold the power button down for at
least two seconds. (To switch power off, momentarily press the power button
again.) The instrument takes a few seconds to power up, initialize itself, and begin normal operation. During initialization the lower line of the display shows
the manufacturer, model number, firmware version, and the state of battery
charge or the message “External power” if the AC adapter is attached. The
1521 reads important information about the attached probe from the
INFO-CON connector that it subsequently uses to calculate temperature.
The 1521 then performs a memory check of critical parameters, such as the calibration parameters CAL1 and CAL2. During this check the lower line of the
display reads “Checking Memory”. If a “Memory Error” or “Memory Recover”
message is displayed, see Section 12.1, Troubleshooting, for additional information and instructions.

4.7

Measure Temperature
After initialization the upper line of the display will begin to show temperature
measurements sensed at the tip of the probe. Place the tip of the probe into the
object that you want to measure the temperature. DO NOT force the probe or
otherwise allow it to be bent, stressed, or overheated. It can be easily damaged
if misused. For further suggestions on handling the probe and using the 1521
and probe to measure temperature accurately, see Section 6.5. For information
on the various modes of operation of the 1521see Section 7.

5 Parts and Controls
Front Features

Parts and Controls
The functions of the various features of the 1521 are described below.

5.1

Front Features
The front of the 1521 features the LCD display and control buttons.

1521 Handheld Thermometer Readout
User’s Guide

Display-The display shows the current temperature (or resistance) measurement on the large numeric upper portion of the display. It can also show a variety of information on the smaller alphanumeric lower portion such as
minimum, maximum, hold temperatures, delta(x), and other instrument
settings.
Power and Backlight button-This button turns the instrument on or off. If the
power is on, pressing the button for three seconds toggles the backlight on or
off (see Section 6.3). Note: using the backlight drains the battery more
quickly.
ENT (enter) button-This button is pressed to accept changes to a setting and,
in some modes, to store the most recent measurement.
CLR (clear) button-This button cancels changes to a setting and in the
MIN/MAX mode resets the minimum and maximum to the last measurement.
Up and Down buttons-These buttons are used to change values and settings.
MODE button-This button advances through operating modes and programming functions (see Section 7).

5 Parts and Controls
Top and Side Features

5.2

Top and Side Features
Probe Connector

Top View

Side View

Serial Port

Infrared Window
(not used)

DC Power Input

Stand

Figure 2 Top and Side View

The top and side of the 1521 feature the probe connector, DC power input, serial port, and infrared window.
Probe Connector - At the top of the thermometer is the opening where the
probe connector is inserted. The probe must be connected using an INFO-CON
probe connector to measure temperature (see Section 6.6).
DC Power Input-The AC adapter plugs into the DC power input to recharge
the battery and to power the instrument while the battery is being charged (see
Section 6.2).
Serial Port-The RS-232 serial port provides a means of connecting the 1521 to
a computer or a printer using the included serial cable (see Section 8). The
baud rate is fixed at 2400 baud, the linefeed is fixed to ON (all carriage returns
are followed by a linefeed (ASCII decimal 10), and the duplex is fixed to Half
disabling the echo.
Infrared Window-The infrared window has no functionality.
15

1521 Handheld Thermometer Readout
User’s Guide

5.3

Back Features
See Figure 4 on page 19.
Stand-The stand at the back of the 1521 can be flipped down to prop up the instrument for better viewing.
Battery Compartment- Behind the stand is the compartment that contains the
battery pack. The battery pack can be accessed if necessary by opening the battery cover with a small Philips screwdriver (see Section 6.1).
Serial Number Label-Also behind the stand is the serial number label that
uniquely identifies the instrument.

5.4

Internal Features
The significant components inside the 1521 are described here.
Battery-The 1521 has an internal rechargeable battery pack that can be recharged by the AC adapter without removing the battery. It can be used and recharged many times. If necessary, it can be easily removed and replaced (see
Section 6.1).
Micro-controller-The 1521 uses a micro-controller to control all its functions.
The micro-controller manages the measurement process, retrieves measurement
data from the analog-to-digital converter (ADC), places measurements and
other information on the display, senses button actions, reads battery status information from the power control circuit, and handles communications through
the serial port.
Power Control Circuit-The power control circuit manages the electrical power
that drives all the circuits. It handles switching between the two sources of
power (DC input and battery pack), regulates voltages, monitors the state of
battery charge, and manages battery charging.
Analog-to-Digital Converter and Measurement Circuit-The ADC takes an
analog signal produced by the probe and converts it to a digital value that can
be read by the micro-controller. The ADC used in the 1521 was selected for its
excellent resolution, linearity, and stability. The measurement circuit built
around the ADC was carefully designed for accuracy and stability to match the
ADC. The measurement circuit allows complete rejection of probe wire resistance effects that would otherwise seriously limit accuracy. Offsets from
sources such as thermoelectric EMF are also completely rejected. This is done
using a current reversal technique with the probe current alternating at a rate of
one cycle per second. Self-heating is minimized by using low sensing currents.
For PRTs the current is only 0.5 mA. For thermistors the current is only 0.005
mA.

5 Parts and Controls
Accessories

5.5

Accessories
The 1521's accessories and their features are described here.
AC Adapter-The AC adapter recharges the internal battery pack and can also
be used to supply power to operate the 1521 while the battery is being charged
(see Section 6.2).
Serial Cable-The serial cable can be used to connect a computer or a printer to
the 1521 through its serial port (see Section 8).
INFO-CON Connector-Hart’s unique INFO-CON connector allows the probe
to be easily attached and detached from the 1521. It also contains a memory device that stores information about the probe and automatically transfers
this data to the 1521 when the probe is attached. This ensures that the settings used to measure and calculate temperature always match the probe being
used (see Section 6.6).

IN
ON

-C

Figure 3 INFO-CON Connector

Probe-The probe acts as the temperature sensor. Its resistance depends on its
temperature. The 1521 precisely measures the resistance of the probe and uses
the coefficients stored in the INFO-CON connector to calculate its temperature
(see Section 6.5). The following probe options are available.

1521 Handheld Thermometer Readout
User’s Guide

Ordering Information
Cal Uncertainty and
Repeatability

Typical Drift
(1 year)

1/4” x 12” or 15”
(6.35 x 305 or 381 mm)

±0.015°C

±0.03°C

–200 to 660°C

1/4” x 12” or 15”
(6.35 x 305 or 381 mm)

±0.015°C

±0.03°C

Pt-100 Ohm, 4-wire

–200 to 450°C

1/4” x 12” (6.35 x 305 mm)

±0.025°C

±0.01°C

Pt-100 Ohm, 4-wire

–200 to 300°C

3/16” x 6” (4.76 x 152 mm)

±0.025°C

±0.01°C

Model

Type

Range

Size

5626

Pt-100 Ohm, 4-wire

–200 to 660°C

5628

Pt-25 Ohm, 4-wire

5614
5613
5612

Pt-100 Ohm, 4-wire

–200 to 450°C

3/16” x 9” (4.76 x 229 mm)

±0.025°C

±0.01°C

5627–6

Pt-100 Ohm, 4-wire

–200 to 300°C

3/16” x 6” (4.76 x 152 mm)

±0.035°C

±0.13°C

5627–9

Pt-100 Ohm, 4-wire

–200 to 450°C

3/16” x 9” (4.76 x 229 mm)

±0.035°C

±0.13°C

5627–12

Pt-100 Ohm, 4-wire

–200 to 450°C

1/4” x 12” (6.35 x 305 mm)

±0.035°C

±0.13°C

5610-6

10K-ohm Thermistor

0 to 110°C

1/8” x 6” (3.2 x 152 mm)

±0.02°C

±0.01°C

5610-9

10K-ohm Thermistor

0 to 110°C

1/8” x 9” (3.2 x 229 mm)

±0.02°C

±0.01°C

5611

10K-ohm Thermistor

0 to 110°C

0.07” x 0.55” (1.8 x 14 mm)

±0.02°C

±0.01°C

5611T

10K-ohm Thermistor

0 to 110°C

0.11” x 1.1” (2.8 x 28 mm)

±0.02°C

±0.01°C

5640

4K-ohm Thermistor

0 to 60°C

1/4” x 9” (6.35 x 229 mm)

±0.0015°C

±0.005°C

LogWare Software - The Model 9934 LogWare software is a one channel data
acquisition software. This software can be used with your 1521 thermometer to
collect and graph data.
Carrying Cases - There are two types of cases available for your 1521 thermometer. The Model 9318 case is a hard case for carrying the thermometer and
a 12" probe. The Model 9321 case is a soft case with a belt clip and a probe
slot.

6 General Operation
Battery

General Operation
This section explains the details of the operation of the 1521 with its components and accessories.

6.1

Battery
The 1521 has a built-in nickel-metal-hydride battery pack that can power the
instrument for about 18 hours before needing to be recharged. The battery will
discharge much more quickly if the display backlight is used often. The battery
charge remaining or the message “External Power” is shown on the display
when the instrument is switched on. The battery percentages are approximate
and should be used as general guidelines when determining the length of
charge remaining.
The battery is recharged in situ (while in place) using the AC adapter that’s
provided. Plug the AC adapter into an AC socket of the appropriate voltage as
noted on the AC adapter (normally 115V, optionally 230V). Connect the DC
plug of the adapter into the DC input of the 1521 located on the right side. The
battery will be charged as necessary whether or not the instrument is switched

Stand in vertical position

FLUKE CORPORATION
HART SCIENTIFIC DIVISION
MADE IN USA

FLUKE CORPORATION
HART SCIENTIFIC DIVISION
MADE IN USA
MODEL: 1521
SERIAL NO: 941234

MODEL: 1521
SERIAL NO: 941234

Battery cover
Battery

Battery plug
Battery connector

Battery removed

Battery installed and connected

Figure 4 Battery Installation

1521 Handheld Thermometer Readout
User’s Guide

on. The power control circuit inside the instrument manages battery charging
and will stop charging the battery automatically when it’s fully charged. It normally takes about four hours to fully charge the battery. The instrument can be
operated while the battery is being charged.
CAUTION: DO NOT leave the AC adapter plugged in for more than 24
consecutive hours or, the battery life could be degraded.
The battery pack can be used for a minimum of 500 charge-discharge cycles
before needing to be replaced. Replacement battery packs are available from
the manufacturer. The battery pack can be easily removed and replaced in the
field by following this procedure:
1.

Power the 1521 off and unplug the AC adapter from the unit.

With the 1521 facing down, lift the stand to expose the battery cover (see
Figure 4). Remove the battery cover screw with a small Philip’s screwdriver. Place the screw in a safe place so it won’t get lost. Remove the
battery cover to access the battery pack.

Pull the battery pack out. Note the orientation of the battery plug on
the connector. The new battery pack will be plugged in the same direction. Gently pull the battery plug off the connector.

Attach the polarized plug of the new battery pack onto the connector in
the same direction as before (see Figure 4 on page 19). Place the battery
pack in the battery compartment.

Close the battery cover and replace the screw.

Plug in the AC adapter and charge for a minimum of four hours for its
initial charge.

WARNING: Used batteries must be disposed of properly. Check your local regulations for additional information. You may return used batteries
to the manufacturer. Never dispose of batteries in fire as this may result in
explosion with the possibility of personal injury or property damage.

6.2

DC Power Source
The DC power source provides power to charge the battery. It can also be used
to power the 1521 while the battery is being charged. The AC adapter provided
with the 1521 is intended to be used for these purposes. Use only the AC

6 General Operation
Power Button

adapter supplied with the instrument. The DC power source plugs into the DC
power input on the right side of the 1521.

–
+

Figure 5 12V DC Power Source Polarity

WARNING: The AC adapter has circuits with high voltages inside that
could present danger of electric shock or fire if exposed. If the AC adapter
is damaged in any way or becomes hot, discontinue its use immediately,
disconnect it from any AC supply, and have it replaced. Do not attempt to
open, repair, or continue using a damaged or defective AC adapter.

6.3

Power Button
The power button controls power to the instrument and operates the backlight.
The following table summarizes the power button functions.

6.4

Function

Action

Power on

Press the power button for at least two seconds when the power is off

Power off

Press the power button momentarily (1/2 second or less) when the power is on

Backlight on

Press the power button for three seconds or more when the power is on and
the backlight is off

Backlight off

Press the power button for three seconds or more when the backlight is on

Display and Backlight
The display shows measurement data and other information depending on the
selected mode.
The upper part of the display continually shows the most recent measurement.
It uses large digits for easy viewing. A new measurement is produced and displayed every second. The unit associated with the measurement is shown in
21

1521 Handheld Thermometer Readout
User’s Guide

smaller type to the right of the measurement. The possible units are degrees
Celsius (C), resistance in ohms (Ω), degrees Fahrenheit (F), Kelvin (K), and
degrees Rankine (R). The units can be easily changed by placing the display in
the units setting mode using the MODE button (see Section 7.5).
The lower part of the display has various functions depending on the selected
mode. It has smaller alphanumeric characters. It can be used to display minimum and maximum measurements, delta(x) measurements, or measurements
stored in memory. It is also used to view and set various operating parameters.
The mode is easily changed using the MODE button. (See details on the various modes beginning with Section 7.)
The display has a backlight that can be switched on for better viewing in dim
light. The backlight is switched on and off by pressing and holding the power
button for three seconds (see Section 6.3 above). Note: The battery discharges more quickly when the backlight is used.

6.5

Probe
The probe is used to sense temperature. The probe attaches to the 1521 using a
Hart INFO-CON probe connector that plugs into the top of the instrument. The
probe connector must be properly programmed with the correct characteristics of the probe for measurements to be accurate (see Section 6.6).
The 1521 can be used with various types of PRT and thermistor probes:
• ITS-90 calibrated 25Ω or 100Ω PRT
• IEC-751 or DIN-43760 PRT (RTD)
• Callendar-Van Dusen calibrated 100Ω PRT
• YSI-400 series or equivalent 2252Ω thermistor
• Steinhart-Hart thermistor polynomial; nominal R(25°C) 2kΩ to 100kΩ
See Section 7.8.8 for details on the various probe types and their programming.
The 1521 cannot be used with thermocouples.
The 1521 can be used with probes having two, three, or four wires. Three wires
allow partial compensation for wire resistance. The 1521 measures three-wire
probes using the following algorithm. It measures the sensor resistance, including the lead resistance in C2. The 1521 then directly measures the resistance in
the C1 lead of the sensor. The 1521 then subtracts the measured C1 lead resistance from the measured sensor resistance (including the C2 lead resistance) to
obtain the sensor resistance used to calculate temperature. Note: This algorithm
assumes that the lead resistance of C1 and C2 are equal. If C1 and C2 have different resistance there will be an error in the calculated sensor resistance equal
to this difference. Four wires allow complete rejection of wire resistance and
should be used when the best accuracy is desired. The 1521 wire setting must
be set to match the actual number of wires of the probe (see Section 7.8.14).

6 General Operation
INFO-CON Connector

Temperature is generally sensed at the tip of the probe. To get an accurate temperature measurement the probe sheath should be well immersed, with adequate depth and fit, into the medium to be measured.
CAUTION: Probes are fragile devices that can be easily damaged by mechanical shock, overheating, and absorption of moisture or fluids in the
wires or hub. Damage may not be visibly apparent but nevertheless can
cause drift, instability, and loss of accuracy. Observe the following precautions:
Do not allow probes to be dropped, struck, bent, or stressed.
Do not overheat probes beyond their recommended temperature range.
Do not allow any part of the probe other than the sheath to be immersed in
fluid.
Do not allow the probe hub or wires to be exposed to excessive temperatures.
Keep the probe wires clean and away from fluids.

6.6

INFO-CON Connector
The probe connects to the top of the 1521 using a Hart INFO-CON connector
(see Figure 3 on page 17). The probe connector will fit snugly and lock into
place when it is fully inserted. The connector includes a memory device that
stores the unique characteristics of the probe, allowing the instrument to measure temperature accurately. Generally, the probe will be purchased with the
connector attached and programmed by the factory. Connectors can be purchased separately and installed onto probes by the user. The INFO-CON can be
programmed directly from the 1521 by authorized personnel.
If it is necessary to install the INFO-CON onto a probe in the field follow the
diagram below for connecting the wires of the probe to the connector terminals.
Before opening the INFO-CON case, be sure to be grounded with an ESD strap
to avoid damaging the memory chip. For four-wire probes, one pair of wires attaches to terminals C1 and P1 and the other pair attaches to terminals C2 and
P2. (C1 and C2 source current and P1 and P2 sense the potential.) If a shield
wire is present it should be connected to the GND terminal (see Figure 6).
A three-wire or two-wire probe can also be used with the 1521. A three-wire
probe is connected by attaching the common wires to the C1 and P1 terminals
and the other wire to the C2 and P2 terminals. The two-wire probe is connected
by one wire to the C1 and P1 terminals and the other wire to C2 and P2. Again,
any shield wire should be connected to the GND terminal (see Figure 6). Rec-

1521 Handheld Thermometer Readout
User’s Guide

ognize that accuracy may be significantly degraded using a two-wire connection because of wire resistance.

GND
C1
P1

C2
P2

GND
C1
P1

C2
P2

Short

Four-wire Connection

Three-wire Connection

Figure 6 Probe Wiring Diagrams

Short

Two-wire Connection

7 Display Functions

Display Functions
The 1521 operates in any of several modes which determine what information
is visible in the lower alphanumeric portion of the display. The MODE button
changes the mode. This button can be pressed repeatedly until a desired mode
is set. The various modes are listed below in the order they appear. (See Figure
7).
Blank - No data shown
Min/Max - Minimum and maximum measurements (CLR to reset)
Hold - Data stored in the hold registers
Delta(x) - Delta from reference measurement (ENT to set reference)
Units: C/Ω/F/K/R - Set the units of measurement
Rate: 00000 - Set the period for serial transmission
Resol: XXX.XXX - Set the display resolution
CAL MODE - Set probe and instrument calibration parameters (MODE
button must be held for three seconds) See Section 7.8.
Note: Units, Rate, and Resol are temporary modes. The instrument will return
to Delta(x) mode if left in one of these modes when the power is cycled.

1521 Handheld Thermometer Readout
User’s Guide

Each of these operating modes is described in the sections that follow.

Blank Mode
MODE

button
Delta(x) Mode

Min/Max Mode
MODE

button

MODE

Set Units

Hold Mode
MODE

button

MODE

button

Set Rate
MODE

button

Set Resolution
MODE

button

any mode
MODE

button (3 seconds)

Cal Mode
Figure 7 Operating Modes Flowchart

7.1

Blank Mode
This mode is identified by “Blank” that temporarily appears on the display.

7 Display Functions
Min/Max Mode

In this mode nothing appears on the alphanumeric portion of the display. Use
this mode if you are only interested in the latest measurements and want to simplify the appearance of the display.
The message “Prb cal expired”, “Mtr cal expired”, “Recharge Needed”, or
“Probe is locked” may be displayed. See Section 11.1.

7.2

Min/Max Mode
This mode is identified by “Min/Max” that temporarily appears on the display.
In this mode the maximum and minimum measurements taken since the last
time the function was cleared appears on the display. The minimum appears on
the left and the maximum appears on the right. The resolution of the displayed
values may be changed using the Resolution mode (see Section 7.7). Pressing
the CLR button at anytime while in this mode clears the minimum and maximum values setting them to the last measurement. Both the minimum and maximum are reset to 0°C (32°F) when the instrument is powered up.
The message “Prb cal expired”, “Mtr cal expired”, “Recharge Needed”, or
“Probe is locked” may be displayed. See Section 11.1.

7.3

Hold Mode
This mode is identified by “Hold” that temporarily appears on the display.
In this mode the data stored in one of the hold registers appears on the display.
There are six hold registers. The resolution of the Hold register values may be
changed using the Resolution Mode (see Section 7.7). The Up and Down buttons are used to select a desired hold register for viewing. The ENT button is
used to store a measurement in the next available register.
The message “Prb cal expired”, “Mtr cal expired”, “Recharge Needed” , or
“Probe is locked” may be displayed. See Section 11.1.

7.4

Delta(x) Mode
This mode is identified by “Delta(x)” that temporarily appears on the display.
In this mode the delta between the measurement and a previously stored reference value appears on the right side of the display. The reference value appears
on the left. The resolution of the reference value may be changed using the
Resolution mode (see Section 7.7) if necessary. The ENT button stores the
present measurement as the reference value.
The message “Prb cal expired”, “Mtr cal expired”, “Recharge Needed” , or
“Probe is locked” may be displayed. See Section 11.1.

1521 Handheld Thermometer Readout
User’s Guide

7.5

Units
This mode is identified by “Units: C/Ω/F/K/R” that appears on the display.
This mode allows you to select the unit of measurement: C for degrees Celsius,
Ω for resistance in ohms, F for degrees Fahrenheit, K for Kelvin, and R for
Rankine. The Up and Down buttons are used to select one of the displayed
units. The underline cursor indicates which of the units is selected. The ENT
button stores the selection. If the MODE button or CLR button is pressed without pressing ENT the unit remains unchanged. Once the unit is selected, subsequent measurements appear in that unit. The Min/Max and Delta(x) values
are automatically converted when changing to C, K, F, or R units.
When measuring in units of ohms, make sure that the appropriate probe type
has been selected in the Cal Mode menu. For example, to measure a sensor between 0 and 400 ohms, set the units to ohms and select the probe type "CVD".
To measure a sensor between 400 and 500K ohms, set the units to ohms and select the probe type "THERM".

7.6

Rate
This mode is identified by “Rate: 00000" that appears on the display.
This mode allows you to set the samples that are transmitted through the serial
port. The sample for a 2-wire and a 4-wire probe is approximately one second
and for a 3-wire probe is approximately two seconds. For example, if the rate is
set to 2, every other sample is sent through the serial interface. Note: If the
probe wire is set to 3, the time between samples is twice as long. A value of 0
disables transmission. The Up and Down buttons are used to increase or decrease the value for the underlined digit. The ENT button moves to the next
digit. If the ENT button is pushed when the last digit is underlined, the setting
is stored. If the MODE button or CLR button is pressed, the value remains unchanged. Once the value is set, measurements are transmitted through the serial
port at the given interval.

7.7

Resolution
This mode is identified by “Resol: XXX.XXX” that appears on the display.
This mode allows you to set the resolution of measurements to one, two, or
three digits after the decimal point. The Up and Down buttons are used to increase or decrease the resolution setting. The ENT button stores the setting. If
the MODE button or CLR button is pressed, the setting remains unchanged.
Once the resolution is set, measurements are displayed and transmitted from
the serial port at the given resolution if possible. The resolution may be reduced
if necessary for large values of temperature or resistance.

7 Display Functions
CAL MODE

7.8

CAL MODE
The calibration menu contains functions for setting probe and instrument calibration parameters. If a probe parameter is changed, the probe parameter is uploaded into the INFO-CON probe connector when the CAL MODE is exited or
after scrolling through the entire menu. Always check to insure that the parameters have been written to the INFO-CON connector by disconnecting the
probe or by turning the 1521 off and on.
The calibration menu is entered by pressing and holding the MODE button for
three seconds. “CAL MODE” appears on the display. Press the ENT button to
advance. Press the MODE button while in the calibration menu to exit and to
advance to the display mode that follows the display mode that was active before the CAL Mode was entered.
The functions contained in the CAL Mode are listed below in the order they appear. In any of the functions the ENT button stores the displayed value or selection and advances to the next function. The CLR button can be used to
cancel changes to a value or selection and skip to the next function. Use the
ENT button to move from Mtr Due to Prb Due and then to Time. Use the CLR
button to quickly advance through the remaining functions. Many of the functions are in the passcode protected part of the CAL Mode. You must enter the
correct passcode to reach them.
Mtr Due - View the date the instrument is due for calibration
Prb Due - View the date the probe is due for calibration
Time - View and set the real-time clock time-of-day
Passcode - Enter the passcode to advance to the protected functions
Date - View and set the real-time clock date
Probe Lock - Lock or unlock operation of the unit with the current probe
only
Prb # - Set the probe serial number
Prb Type - Select the probe type and temperature calculation
R(.01) [ITS-90 only] - Sets the R(273.16K) probe coefficient
a [ITS-90 only] - Set the a5, a6, a7, a8, a9, a10, or a11 probe coefficient
b [ITS-90 only] - Set the b5, b6, b7, b8, or b9 probe coefficient
c [ITS-90 only] - Set the c6, or c7 probe coefficient
d [ITS-90 only] - Set the d probe coefficient
a4 [ITS-90 only] - Set the a4 or a5 probe coefficient
b4 [ITS-90 only] - Set the b4 or b5 probe coefficient
R(0) [CVD only] - Set the R0 probe coefficient
Alpha [CVD only] - Set the alpha probe coefficient
Delta [CVD only] - Set the delta probe coefficient
29

1521 Handheld Thermometer Readout
User’s Guide

Beta [CVD only] - Set the beta probe coefficient
b0 [Therm only] - Set the b0 probe coefficient
b1 [Therm only] - Set the b1 probe coefficient
b2 [Therm only] - Set the b2 probe coefficient
b3 [Therm only] - Set the b3 probe coefficient
Probe Wires - Set the number of wires of the probe
PCal - Set the probe calibration date
PDue - Set the probe calibration due date
Filter - Set the digital filter time constant
MCal - Set the instrument calibration date
MDue - Set the instrument recalibration due date
CAL1 - Set the 0 to 400Ω instrument calibration parameter
CAL2 - Set the 400Ω to 500 kΩ instrument calibration parameter
The calibration functions are described in detail in the following subsections.

7.8.1

Mtr Due
This function displays the date the 1521 is due for calibration. The date cannot
be changed with this function.

7.8.2

Prb Due
This function displays the date the probe is due for calibration. The date is
stored in the INFO-CON probe connector. The date cannot be changed with
this function.

7.8.3

Time
This function displays and sets the time of day. The time is always set, displayed, or printed in 24-hour format. To set each time segment use the Up and
Down buttons. Use the ENT button to move between time segments and to
save the changed values. The CLR button moves to the next function.

7.8.4

Passcode
All functions below this function are protected by a pass-code so that only authorized users can access them. The passcode must be entered correctly to continue. If the passcode is entered incorrectly or the MODE or CLR buttons are
pressed, the message “Invalid Passcode” is displayed and the instrument is returned to the next display mode after the display mode that was active before
the CAL Mode was entered.
Each individual instrument has its own unique passcode. The passcode number
is given on a notice provided with this instrument. The equipment manager is
responsible for keeping the passcode number stored in a proper location and

7 Display Functions
CAL MODE

ensuring that it is not lost or forgotten. If necessary the passcode can be restored by contacting the manufacturer. To enter the passcode use the Up and
Down buttons to set each digit of the passcode and the ENT button to move to
the next digit on the right. Press ENT twice when all digits are entered to move
to the next function. If the passcode is entered correctly the next function in the
CAL Mode will appear.

7.8.5

Date
This function displays the present date and allows it to be changed. This function is placed in the passcode protected part of the CAL Mode since the calibration due warning messages depend on the present date as well as the stored due
dates. Use the Up and Down buttons to set each date segment and the ENT
button to move between the date segments. Press ENT when all digits are entered to save the changed values. The CLR button moves to the next function.

7.8.6

Probe Lock
This function locks or unlocks operation of the unit with the presently connected probe only. If probe lock is set to ON, the instrument can only be used
to display temperature with the probe attached when probe lock was set ON. If
probe lock is ON and a different probe is attached the instrument will display
the serial number of the connected probe, ‘PRT: xxxxxxxxxx’, and then the
message “Probe is locked”. Measuring will be disabled. If probe lock is OFF
the instrument can be used with any probe. To lock the instrument with a new
probe, set probe lock OFF, attach the new probe, and then set probe lock ON
again. Probe lock ON also disables access to the probe parameters that follow
in the menu. The probe parameters, beginning with the probe serial number,
will only appear in the menu if probe lock is OFF. To set probe lock use the Up
and Down buttons to select ON or OFF and press the ENT button to store and
continue.

7.8.7

Prb #
This function displays the serial number of the probe and allows it to be set.
The probe serial number is stored in the INFO-CON probe connector. Use
the Up and Down buttons to set each digit and the ENT button to move to the
next digit on the right. Press ENT when all digits are entered.

7.8.8

Prb Type
This function specifies the type of probe and its characterization. It allows the
1521 to use the appropriate algorithm to calculate temperature from the measured resistance of the probe. The functions that follow the probe conversion
function for setting probe characterization coefficients depend on the selected
probe type. The table below lists the probe types and the corresponding
coefficients.
Probe Type

Description

Coefficients

1521 Handheld Thermometer Readout
User’s Guide

ITS-90

PRTs calibrated to ITS-90

R(.01), a, b, c, d, a4, and b4

IEC751

PRTs (RTDs) conforming to IEC-751

none

CVD

PRTs characterized by the Callendar-Van Dusen
equation

R0, Alpha, Delta, and Beta

YSI400

Thermistors matching the YSI-400 series

none

THERM

Thermistors characterized by the thermistor
polynomial

b0, b1, b2, and b3

Each of the conversion options is explained in the following sections along
with their associated coefficients, if they have any. The probe type and associated coefficients are stored in the INFO-CON probe connector. Use the Up and
Down buttons to select the probe type and the ENT button to store and
continue.
Each of the coefficients that follow the probe type, if there are any, are set in
the usual way. Use the Up and Down buttons to set each digit and the ENT button to move to the next digit to the right. Press ENT when all digits are entered.

7.8.9

ITS-90
The ITS-90 type is for PRTs calibrated and characterized using the International Temperature Scale of 1990 equations. This type of probe generally has
excellent accuracy (0.005 to 0.025°C), a wide operating range (–180°C to
420°C or higher), but may be rather expensive. The coefficients that appear
when ITS-90 is selected are “R(.01)”, “a”, “b”, “c”, “d”, “a4", and ”b4".These
should be set to the coefficient values that appear on the PRT calibration certificate according to the following table.
Unused coefficients must be set to 0.
1521 Coefficients

Certificate Value

R(.01)

Rtpw

a5, a6, a7, a8, a9, a10, or a11

b5, b6, b7, b8 or b9

c6 or c7

a4 or a5

b4 or b5

Consider the following examples.
Example 1:

A PRT was calibrated to ITS-90 and its calibration certificate states values for
coefficients R(273.16K), a4, b4, a8, and b8. Set the 1521 coefficients to the
certificate values as follows.
1521 Coefficients

Certificate Value

R(.01)

R(273.16K)

0.0

Example 2:
A PRT was calibrated to ITS-90 and its calibration certificate states values for
coefficients R(273.16K), a5, and b5. Set the 1521 coefficients to the certificate
values as follows.

7.8.10

1521 Coefficients

Certificate Value

R(.01)

R(273.16K)

0.0

IEC751
The IEC-751 probe type is for standard PRTs (RTDs) conforming to the
IEC-751 or DIN-43760 standards. This type of probe is generally low cost and
has a wide operating range (–180°C to 420°C or higher), but has limited accuracy (0.15°C to 4°C). There are no user programmable coefficients associated
with this probe type.

7.8.11

CVD
The CVD (Callendar-Van-Dusen) type is used with PRTs that have unique calibration coefficients or do not match the IEC-751 specification. This type of

1521 Handheld Thermometer Readout
User’s Guide

higher), and has moderate accuracy (0.05°C to 1°C). This type uses the
Callendar-Van Dusen equation to calculate temperature from resistance:
⎧ ⎧
⎡
1 ⎛ t
⎞ ⎤⎫
t≥0
− 1⎟ ⎥⎬
⎜
⎪R0 ⎨1 + α ⎢t − δ
⎝
100 100 ⎠ ⎦⎭
⎣
⎪ ⎩
r( t[ °C ]) = ⎨
3
⎧
⎡
⎤⎫
⎪R ⎨1 + α ⎢t − δ t ⎛⎜ t − 1⎞⎟ − β ⎛⎜ t − 1⎞⎟ ⎛⎜ t ⎞⎟ ⎥⎬ t < 0
0
⎝
⎠
⎝
⎠
⎝
⎠
⎪ ⎪
100 100
100
100 ⎥⎦⎭
⎢⎣
⎩ ⎩

The coefficients R0, α, δ, and β can be set by the user using the functions
“R0", ”Alpha", “Delta”, and “Beta” respectively. When editing “Alpha”, there
is an assumed exponent of 10–3 (i.e. 3.8500 is actually 0.0038500).

7.8.12

YSI-400
The YSI-400 type is for 2252Ω thermistors matching the characteristics of the
YSI-400 series of thermistors. This type of probe generally is low cost, has a
limited operating range (–40°C to 150°C), good accuracy (0.1°C to 0.4°C), and
excellent resolution (0.002°C). There are no user programmable coefficients associated with this probe type. Temperature is converted from resistance based
upon a standard YSI-400 table resident in the instrument.

7.8.13

THERM
The THERM thermistor type is for thermistors that have unique calibration coefficients or do not match the YSI-400 specification. This type of probe generally has moderate cost, a limited operating range (–40°C to 100°C), excellent
accuracy (0.005°C to 0.02°C) and excellent resolution (0.002°C). This type
uses the Steinhart-Hart equation in the following form:
R( T[ K ])[ Ω ] = exp[ b0 + b1 T −1 + b2 T −2 + b3 T −3 ]

The coefficients b0 through b3 are usually found on the calibration certificate
of the probe. These coefficients are set with the functions “b0", ”b1", “b2", and
”b3". In some cases the equation is used without the b2 term. For this case, the
“b2" coefficient should be set to 0. Consider the following examples.
Example 1:
A thermistor has coefficients for the equation ln(R) as a function of T given as
a, b, c, and d. Set the 1521 coefficients to the certificate values as follows:

1521 Coefficients

Certificate Value

7 Display Functions
CAL MODE

Example 2:
A thermistor has coefficients for the equation ln(R) as a function of T given as
a, b, and c. Set the 1521 coefficients to the certificate values as follows:

7.8.14

1521 Coefficients

Certificate Value

0.0

Probe Wires
This function sets the number of connecting wires in the probe. The probe
wires setting is stored in the INFO-CON connector. The 1521 can be used with
probes that have two, three, or four wires. Three wires connecting the probe
sensor instead of two allows the 1521 to partially cancel measurement error due
to the resistance of the wires. With four wires the 1521 can completely cancel
the error. The internal measurement circuit is configured differently depending
on the number of wires. Important—The 1521 will try to calculate a measurement even if the wire settings are incorrect. Therefore, the Probe
Wires setting must match the actual number of wires or loss of accuracy
will result. Use the Up and Down buttons to set the value and press the ENT
button to store and continue.

7.8.15

PCal
This function shows the date the probe was calibrated and allows it to be set.
The date is stored in the INFO-CON connector and is used simply for reference. Use the Up and Down buttons to set each date segment and the ENT button to move to the next date segment to the right. Press ENT when the date is
correctly entered. Press CLR to move to the next function without changing the
date.

7.8.16

PDue
This function shows the date the probe is due for calibration and allows it to be
set. The date is stored in the INFO-CON connector. The probe due date is regularly checked against the present date and if the calibration has expired the user
is alerted with the message “Prb cal expired”. This message only disappears
when the probe is recalibrated and the probe calibration due date is set to a future date. To set the date, use the Up and Down buttons to set each date segment and the ENT button to move to the next date segment to the right. Press
ENT when the date is correctly entered. Press CLR to move to the next function without changing the date.
35

1521 Handheld Thermometer Readout
User’s Guide

Note: Probe parameters are uploaded to the INFO-CON connector at this point.

7.8.17

Filter
The digital filter helps to smooth variations in the measurements and improve
resolution. A negative effect of filtering is that it tends to slow the response to
changes in temperature. You can increase the filter time constant to further improve accuracy and resolution or decrease the time constant to reduce the response time. Valid values are any number between 0.0 and 60.0 seconds. A
value of 0.0 disables the filter. The default is 0.0. Use the Up and Down buttons to set the value and press the ENT button to store and continue. Press
CLR to move to the next function without changing the filter.

7.8.18

MCal
This function shows the date the 1521 was calibrated and allows it to be set.
The date is used simply for reference. Use the Up and Down buttons to set
each date segment and the ENT button to move to the next date segment on the
right. Press ENT when the date is correctly entered. Press CLR to move to the
next function without changing the date.

7.8.19

MDue
This function shows the date the 1521 is due for calibration and allows it to be
set. The meter calibration due date is regularly checked against the present date
and if the calibration has expired the user is alerted with the message “Mtr cal
expired”. The message will only disappear when the 1521 is recalibrated and
the meter calibration due date is set to a future date. To set the meter calibration
due date use the Up and Down buttons to set each date segment and the ENT
button to move to the next date segment to the right. Press ENT when the date
is correctly entered. Press CLR to move to the next function without changing
the date.

7.8.20

CAL1 and CAL2
The CAL1 and CAL2 meter calibration parameters calibrate the 0 to 500Ω
measurement range and the 0 to 500 kΩ measurement range respectively. These
parameters directly affect the accuracy of the 1521 and are only to be altered by
an authorized, qualified technician as part of a regular instrument calibration
operation. Refer to the calibration procedure in Section 9. Use the Up and
Down buttons to set the value and press the ENT button to store and continue.
Press CLR to move to the next function without changing the date.

8 Communications Interface
RS-232 Connection

Communications Interface
Remote communications allows an external device, such as a computer, to communicate with the 1521 to obtain measurement data and control its operation.
Communication is accomplished with various commands issued to the 1521
through the RS-232 serial port.

8.1

RS-232 Connection
The three-conductor jack for the serial port is located on the top of the 1521
near the probe connector. One serial cable is included with the 1521. Additional
or longer cables, of three meters or less, can be constructed by following the
wiring diagram shown in Figure 8. Note: The TxD line on one side connects
to the RxD line on the other and vice-versa. To reduce the possibility of electrical interference, the serial cable should be shielded with low resistance between the connector and the shield. It should not be much longer than is
necessary. The protocol for serial communications is 8 data bits, 1 stop bit, and
no parity. Use no flow control. The baud rate is fixed at 2400, the linefeed to

GND
GND
RxD

TxD

RxD

9
8
7
6

5
4
3
2
1

Figure 8 RS-232 Wiring

ON (all carriage returns are followed by a linefeed (ASCII decimal 10)), and
the duplex to HALF disabling echo.
The serial port can be used to transmit measurements to a computer or printer.
It can also be used to change settings of the 1521 from a computer or interface
with software. A full list of commands follows in Section 8.2.
Commands sent to the 1521 must end with an EOS character which is a carriage return (ASCII decimal 13) or linefeed character (ASCII decimal 10).
Commands can be sent with upper or lower case letters. Data returned from the
1521 ends with a carriage return and a linefeed.

8.2
8.2.1

Communication Command List
Primary Commands
The following group of commands read or set various functions.
Response
Format

Response
Example

t: 999.999
{C, O, F, R, or K}
mm-dd-yyyy
hh:mm:ss

t: 125.745 C
03-01-1999
15:49:15

Read measurement, simple format f[etch?]
rea[d?]
me[asure?]

fetch?
read?
meas?

t: 999.999
{C, O, F, R, or K}

t: 25.587 C

Read minimum

m[inimum]

min

min: 999.999
{C, O, F, R, or K}

min: -14.653 C

Read maximum

ma[ximum]

max

max: 999.999
{C, O, F, R, or K}

max: 416.781 C

Description

Command

Example

Read measurement, extended
format

t[emperature]

Clear minimum and maximum

cl[ear]

clear

Read a hold register

h[ld]

hld6

hld: 999.999 {C, O, F, hld6: 26.553 C
R, or K}

Range

can be 1 to
6

8 Communications Interface
Communication Command List

Description

Command

Example

Set resolution digits

re[solution]=n

res=1

Read time

ti[me]

time

Response
Format

Response
Example

Range
1 to 3

ti: hh:mm:ss

ti: 16:23:45

Set time
ti[me]=hh:mm:s ti=08:15:0
0
Note: You must set hours, min- s
utes, and seconds for the time to
be set correctly.

00:00:00 to
23:59:59

Read identification information

*i[dn?]

*idn?

,
,
,

2.11
Hart,
1521,
95001,

Read model and firmware version

*v[ersion]

*ver

ver.,

ver.1521,
2.11

Legend:

[] Optional Command data
{} Returns either information
n Numeric data supplied by user
9 Numeric data returned to user
x Character data returned to user

8.2.2

Calibration Commands
The following group of commands directly or indirectly affect the accuracy of
the instrument. These commands should only be used by qualified, authorized
personnel. Calibration parameters can only be changed if protection is disabled by entering the proper pass-code using the command *pas= ddddd.
Entering an invalid passcode or cycling the power re-establishes protection of
the calibration parameters. The parameters can be read without disabling the
passcode protection.
Response
Format

Response
Example

date

da: yyyy-mm-dd

da: 1999-03-28

*pas

ps:9

ps:0

da[te]=yyyy-mm-dd

da=1999-03-28

Description

Command

Example

Unprotect calibration parameters with the pass-code

*pas[scode]=nnnnn

*pas=12345

Read date

da[te]

Read passcode protection
state
Set date
Read probe serial number

se[rial]

ser

Set probe serial number

se[rial]=xxxxxxxxxx

ser=001

Read probe type

p[robe]

Range

0 or 1
1999-01-01 to
2100-12-31

ser: xxxxxxxxxx

ser: 100231A
0 to 9, A to Z,
., -, /

pr: {ITS-90, IEC751,
pr: ITS-90
CVD, YSI400, THERM}

1521 Handheld Thermometer Readout
User’s Guide

Description

Command

Example

Set probe type

p[robe]=IT[S-90]/
IE[C751]/ C[VD]/
Y[SI400]/ T[HR]

Read ITS-90 R(.01) or CVD R0 r[0]

Set ITS-90 R(.01) or CVD R0

r[0]=n

r0=100.106

Read ITS-90 coefficient

a/b/c/d/a4/b4

Set ITS-90 coefficient

a/b/c/d/a4/b4=n

a=-2.8644E-5

Read CVD coefficient

al[pha]/de[lta]/be[ta]

Set CVD coefficient

al[pha]/de[lta]/be[ta]=n al=0.0038512

Read THERM thermistor
coefficient

b0/b1/b2/b3

Set THERM thermistor
coefficient

b0/b1/b2/b3=n

b3=-9.944E-12

Read probe wires

wi[res]

Set probe wires

wi[res]=2/3/4

wi=4

Read probe calibration date

pc[al]

pcal

Set probe calibration date

pc[al]=yyyy-mm-dd

pc=1999-03-28

Read probe due date

pd[ue]

pdue

Set probe due date

pd[ue]=yyyy-mm-dd

pd=1999-03-28

Read filter

fi[lter]

Set filter

fi[lter]=n

fi=0

Read low range calibration

*c1

Set low range calibration

*c1=n

*c1=-0.012

Read high range calibration

*c2

Set high range calibration

*c2=n

*c2=-0.9

Read meter calibration date

mc[al]

mcal

Set meter calibration date

mc[al]=yyyy-mm-dd

mc=1999-03-28

Read meter due date

md[ue]

mdue

Set meter due date

md[ue]=yyyy-mm-dd

md=1999-03-28

Legend:

[] Optional Command data
{} Returns either information

Response
Format

Response
Example

Range
ITS-90,
IEC751,
CVD, YSI400,
THERM

r0: 9999.999

r0: 100.035

{a/b/c/d/a4/b4}:
-9.999999E-99

a: -2.8644101E-5

1 to 900

1.0 to 9.9e-18
{al/de/be}: 9.99999999 al: 0.0038123
E+/-18
{b0/b1/b2/b3}:
9.999999e-99

b3: -9.944070e-12
E+/-18

wi: 9

wi: 4
2,3,4

pc: yyyy-mm-dd

pc: 1999-03-28
1999-01-01 to
2100-12-31

pd: yyyy-mm-dd

pd: 1999-03-28
1999-01-01 to
2100-12-31

fi: 99.99999

fi: 0.5
0.0 to 60.0

c1: 99.999

c1: -0.0121
-1.999 to 1.999

c2: 9999.9

c2: -0.9
-1980.0 to
1980.0

mc: yyyy-mm-dd

mc: 1999-03-28
1999-01-01 to
2100-12-31

md: yyyy-mm-dd

: 1999-03-28
1999-01-01 to
2100-12-31

8 Communications Interface
Communication Command List

Description

Command

Example

Response
Format

Response
Example

Range

n Numeric data supplied by user
9 Numeric data returned to user
x Character data returned to user

9 Calibration
Required Equipment

Calibration
The 1521 should be calibrated at regular intervals to ensure that it continues to
measure with proper accuracy. Calibration should only be done by qualified,
authorized personnel.

9.1

Required Equipment
The following items are required to test and calibrate the 1521:
• 0Ω four-wire resistor (short)
• 25Ω four-wire resistor, uncertainty within 20 ppm (±0.0005Ω)
• 100Ω four-wire resistor, uncertainty within 20 ppm (±0.002Ω)
• 400Ω four-wire resistor, uncertainty within 20 ppm (±0.008Ω)
• 4 kΩ four-wire resistor, uncertainty within 50 ppm (±0.2Ω)
• 10 kΩ four-wire resistor, uncertainty within 50 ppm (±0.5Ω)
• 40 kΩ four-wire resistor, uncertainty within 50 ppm (±2Ω)
• 100 kΩ four-wire resistor, uncertainty within 50 ppm (±5Ω)
• 500 kΩ four-wire resistor, uncertainty within 75 ppm (±37.5Ω)
Each resistor must be attached with an INFO-CON probe connector. The 25Ω,
100Ω, and 400Ω resistors must be programmed with the CVD probe type with
units set to ohms. The 4 kΩ, 10 kΩ, 40 kΩ, 100 kΩ, and 500 kΩ resistors must
be programmed with the THERM probe type with units set to ohms.

9.2

Calibration Procedure
Calibration requires adjustment of the CAL1 and CAL2 parameters at 100Ω
and 10 kΩ respectively (see Section 7.8.20). The calibration parameters can be
accessed from the front panel by pressing the MODE button and holding it for
three seconds, releasing it, then pressing the ENT button (see Section 7.8). You
must enter the pass-code to continue (see Section 7.8.4). The step-by-step procedure is as follows:
1. Connect the 100Ω resistor. Adjust the CAL1 parameter by subtracting the
measured error. For example, if the resistor is exactly 100.000Ω and the 1521
measures 100.029Ω, CAL1 should be adjusted by subtracting 0.029 from the
current value of CAL1.
2. Verify the accuracy at 0Ω, 25Ω, 100Ω, and 400Ω.
3. Connect the 10 kΩ resistor. Adjust the CAL2 parameter by subtracting the
measured error. For example, if the resistor is exactly 10.0000 kΩ and the 1521
measures 10.0029 kΩ, CAL2 should be adjusted by subtracting 2.9 from the
current value of CAL2.
43

1521 Handheld Thermometer Readout
User’s Guide

4. Verify the accuracy at 0Ω, 4kΩ, 10 kΩ, 40 kΩ, 100 kΩ, and 500 kΩ.
5. Set the meter calibration date to the present date (see Section 7.8.18).
6. Set the meter due date to one year from the present date (see Section 7.8.19).

10 Maintenance

Maintenance
• This instrument has been designed with the utmost care. Ease of operation
and simplicity of maintenance have been a central theme in the product
development. Therefore, with proper care the instrument should require
very little maintenance. Avoid operating the instrument in oily, wet, dirty,
or dusty environments.
• If the outside of the instrument becomes soiled, it may be wiped clean
with a damp cloth and mild detergent. Do not use harsh chemicals on the
surface which may damage the LCD or the plastic outside shell.
• If a hazardous material is spilt on or inside the equipment, the user is responsible for taking the appropriate decontamination steps as outlined by
the national safety council with respect to the material.
• Before using any cleaning or decontamination method except those recommended by Hart, users should check with an Authorized Service
Center to be sure that the proposed method will not damage the equipment.
• If the AC adapter becomes damaged, have it replaced immediately. Never
disassemble the AC adapter or attempt to repair it.
• If the instrument is used in a manner not in accordance with the equipment design, the operation of the thermometer may be impaired or safety
hazards may arise.

11 Troubleshooting
An Error Message Is Displayed

Troubleshooting
In case you run into difficulty while operating the 1521, this section provides
some suggestions that may help you solve the problem. Below are several situations that may arise followed by possible causes of the problem and suggested
actions you might take.

11.1

An Error Message Is Displayed
The following table lists possible error messages, their causes, and suggested
actions.
Problem

Solution

“Recharge Needed”

The battery is low and needs to be recharged. When this message first
appears the user has approximately 30 minutes of charge left. If the
battery is not recharged, the 1521 continues to operate until the battery drops below 0% and then automatically shuts itself off after displaying the error message.

“No Probe”

The display shows ‘ - - - - - - - ‘. The instrument is unable to detect
that a probe is connected. Check that a probe with a properly programmed INFO-CON connector is attached.

“Probe is locked”

The incorrect probe is attached. The meter is set to accept only the
probe with the given serial number. Attach the correct probe or have
the instrument properly programmed for the new probe.

“Prb cal expired”

The probe calibration has expired. Have the probe calibrated and
the calibration due date reset.

“Mtr cal expired”

The meter calibration has expired. Have the instrument calibrated
and the calibration due date reset.

“Invalid Passcode”

The passcode entered was not correct. Check the passcode on the
Pass-code Notice sent with the instrument.

The instrument display is blank
when normally it should show
measurements.

Make sure the instrument has power, either from the batteries or
the AC adapter. Verify that the initialization information appears on
the display when the power is switched on. Check to make sure that a
probe is properly connected. Check to make sure that the probe is
programmed properly.

1521 Handheld Thermometer Readout
User’s Guide

Problem

Solution

While attempting to measure resistance the display shows an incorrect value.

Poor or incorrect connection of the probe. A common mistake is to
connect the wires of the probe to the wrong terminals. Check the wiring carefully (see Figure 6).
Open, shorted, or damaged sensor or lead wires. Check the resistance across the sensor using a handheld DMM. Also check the resistance between common pairs of leads. Check to make sure there is
no conductivity between any of the leads and the probe sheath. Use a
good-quality sensor to avoid errors caused by drift, hysteresis, or insulation leakage.
Stem conduction error. Make sure the stem of the probe is immersed in the medium with adequate depth and a tight fit.
Electrical interference. Intense radio-frequency radiation near the
1521 or the probe can induce noise into the measurement circuits resulting in erratic readings. Try eliminating the source of interference or
moving the 1521 to a different location. A well-grounded, shielded cable should be used for the probe.

Memory Check Error

Memory Error.
A non-critical parameter is corrupt in memory. The non-critical
praameters are Units, Rate, Resolution, Filter, and serial port settings.
Press any key and the display reads “Check Settings”. Press any key
again to resume normal operation. Check your current settings for the
specific parameters that were set.
Memory Recover X.
A critical parameter is corrupt and the 1521 can recover the correct
value for that parameter. The critical parameters are CAL1, CAL2,
Passcode, Meter Due Date, Meter Cal Date, and Serial Number.
Press any key and the display reads “Check Settings”. Press any key
again to resume normal operation. Also, check non-critical settings as
in the Memory Error above. The number following the message is
used by authorized technicians.
Memory Invalid!
A critical parameter is corrupt and the 1521 cannot recover the correct value for the parameter. The critical parameters are CAL1, CAL2,
Passcode, Meter Due Date, Meter Cal Date, and Serial Number.
Press any key and the display reads “Contact Factory”. Contact an
Authorized Service Center (see Section 1.3) for assistance in guiding
you through the process of reentering critical parameters.
Note: The parameters stored in the INFO-CON, Probe Wires, Probe
Type, Probe Parameters, are not checked by the meter during memory testing.

11.2

CE Comments

11.2.1

EMC Directive
Hart Scientific’s equipment has been tested to meet the European Electromagnetic Compatibility Directive (EMC Directive, 89/336/EEC). The Declaration
of Conformity for your instrument lists the specific standards to which the unit
was tested.

11 Troubleshooting
CE Comments

The instrument was designed specifically as a test and measuring device. Compliance to the EMC directive is through IEC 61326-1 Electrical equipment for
measurement, control and laboratory use – EMC requirements (1998).
As noted in the IEC 61326-1, the instrument can have varying configurations.
The instrument was tested in a typical configuration with shielded, grounded
probe and RS-232 cables. Emissions may, in non-typical applications, exceed
the levels required by the standard. It is not practical to test all configurations,
as the manufacturer has no control over the probes the user may connect to the
instrument.
11.2.1.1

Immunity Testing
The instrument was tested to the requirements for industrial locations. This allows the instrument to be used in all types of locations from the laboratory to
the factory floor. Criterion B was used for Radiated RF (IEC 61000-4-3) and
Conducted RF (IEC 61000-4-6). Therefore, the operation of the instrument
may be affected by excessive electromagnetic interference and the instrument
may not perform within the normal specification limits in such an environment.
Criterion C was used for Electrostatic Discharge (ESD, IEC 61000-4-2) and
Electric Fast Transit (EFT, Burst, IEC 61000-4-4). If the instrument is subjected to EFT conditions at 2kV, the instrument may require the user to cycle
the power to return to normal operation.

11.2.1.2

Emission Testing
The instrument fulfills the limit requirements for Class A equipment but does
not fulfill the limit requirements for Class B equipment. The instrument was
not designed to be used in domestic establishments.

11.2.2

Low Voltage Directive (Safety)
In order to comply with the European Low Voltage Directive (73/23/EEC),
Hart Scientific equipment has been designed to meet the IEC 1010-1 (EN
61010-1) and the IEC 1010-2-010 (EN 61010-2-010) standards.

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Fluke 1521 Users Manual

1521handheldthermometerreadout cb43b660-52e7-442a-a875-3f0a8863ac0d Fluke Thermometer 1521 User Guide |

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