Fluke Thermometer 1521 User Manual

Hart Scientific  
1521  
Handheld Thermometer Readout  
User’s Guide  
Rev. 571203 ENG  
 
Table of Contents  
i
 
ii  
 
1 Before You Start  
Symbols Used  
1
Before You Start  
1.1  
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  
DC  
Double Insulated  
Electric Shock  
Fuse  
PE Ground  
Hot Surface (Burn Hazard)  
Read the User’s Manual (Important Information)  
Off  
On  
1
 
 
1521 Handheld Thermometer Readout  
User’s Guide  
Symbol  
Description  
Canadian Standards Association  
OVERVOLTAGE (Installation) CATEGORY II, Pollution Degree 2 per IEC1010-1 re-  
fers 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 instru-  
ment 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-hu-  
mid 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 re-  
quirements 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 apply-  
ing 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 ex-  
tremely hot or cold. Cautiously handle probes to prevent personal injury.  
2
 
 
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, immedi-  
ately 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 infor-  
mation. You may return the used batteries to the manufacturer. Never dis-  
pose 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 inter-  
nal or external physical damage, immediately unplug the AC adapter, re-  
move 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.  
3
 
 
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, in-  
stability, 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 im-  
mersed in fluid.  
DO NOT allow the probe hub or wires to be exposed to excessive temper-  
atures.  
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  
Fluke Nederland B.V.  
Customer Support Services  
Science Park Eindhoven 5108  
5692 EC Son  
NETHERLANDS  
Phone: +31-402-675300  
Telefax: +31-402-675321  
Fluke Int'l Corporation  
Service Center - Instrimpex  
Room 2301 Sciteck Tower  
22 Jianguomenwai Dajie  
4
 
 
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  
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  
When contacting these Service Centers for support, please have the following  
information available:  
Model Number  
Serial Number  
Voltage  
Complete description of the problem  
5
 
2 Introduction  
2
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 vari-  
ety 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 cal-  
ibration 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  
7
 
 
3 Specifications and Environmental Conditions  
Specifications  
3
Specifications and Environmental  
Conditions  
3.1  
Specifications  
Resistance Range  
0
0
Ω
Ω
to 500 kΩ  
Resistance Accuracy, PRT, one  
year†  
to 25  
to 400  
Ω
: 0.002  
Ω
Ω
25  
Ω
: 0.008% (80 ppm) of reading  
Resistance Accuracy, thermistor,  
one year†  
0
2 k  
200 k  
Ω
to 2 k  
to 200 k  
to 500 kΩ  
Ω: 0.4Ω  
Ω
Ω
: 0.02% (200 ppm) of reading  
: 0.03% (300 ppm) of reading  
Ω
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,  
–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)  
2.25 k  
Ω
thermistor†  
Temperature Accuracy,  
10 k  
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)  
Ω
Temperature Accuracy,  
100 k  
thermistor†  
0 to 50°C: 0.006°C (0.011°F)  
50°C to 150°C: 0.009°C (0.016°F)  
Ω
Resistance Resolution  
Temperature Resolution  
Probe  
0.001  
Ω
0.001°C, F, K, R  
IEC-751 or DIN-43760 PRT  
Callendar-Van Dusen calibrated PRT; nominal 100  
Ω
ITS-90 calibrated 25  
YSI-400 series or equivalent 2252  
Steinhart-Hart thermistor polynomial; nominal R(25°C) 2k  
100k  
Ω
or 100  
Ω
PRT  
Ω
thermistor  
Ω
to  
Ω
Probe Connector  
Hart Scientific INFO-CON connector  
10  
Maximum Acceptable Probe Lead  
Resistance  
Ω
Probe Excitation Current  
PRT: 0.5 mA  
Thermistor: 5  
μ
A
Measurement Period  
1 second  
9
 
 
1521 Handheld Thermometer Readout  
User’s Guide  
Digital Filter  
Exponential with adjustable time constant (1 to 60 seconds)  
RS-232 serial  
Remote Communications  
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  
Safety  
12 VDC (AC adapter included)  
Rechargeable NiMH batteries (included)  
OVERVOLTAGE (Installation) CATEGORY II, Pollution Degree 2 per  
IEC1010-1 refers to the level of Impulse Withstand Voltage protec-  
tion provided. Equipment of OVERVOLTAGE CATEGORY II is en-  
ergy-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)  
0.4 kg (1.0 lb.)  
Weight  
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 trou-  
ble-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, de-  
creasing linearly to 50% at 40°C  
Pressure: 75kPa-106kPa  
Vibration should be minimized  
Altitude less than 2,000 meters  
Indoor use only  
10  
 
 
4 Quick Start  
Unpacking  
4
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 tempera-  
tures, high voltages, and battery chemicals. Carefully read Section .  
CAUTION: The 1521 and any thermometer probes are sensitive instru-  
ments that can be easily damaged. Always handle these devices with care.  
DO NOT allow them to be dropped, struck, stressed, or overheated.  
4.3  
4.4  
Learn About the Features and Components  
Familiarize yourself with the features and accessories of the 1521 by reading  
Section 5.  
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 tempera-  
ture 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  
4.6  
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 in-  
sert 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  
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 be-  
gin 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 cal-  
ibration 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 infor-  
mation 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.  
12  
 
 
5 Parts and Controls  
Front Features  
5
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.  
13  
 
1521 Handheld Thermometer Readout  
User’s Guide  
Display-The display shows the current temperature (or resistance) measure-  
ment on the large numeric upper portion of the display. It can also show a vari-  
ety 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 program-  
ming functions (see Section 7).  
14  
 
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, se-  
rial 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 in-  
strument 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 bat-  
tery 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 re-  
charged by the AC adapter without removing the battery. It can be used and re-  
charged 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 in-  
formation 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 resis-  
tance 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.  
16  
 
 
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 de-  
vice that stores information about the probe and automatically transfers  
this data to the 1521 when the probe is attached. This ensures that the set-  
tings used to measure and calculate temperature always match the probe being  
used (see Section 6.6).  
INFO  
-
CON  
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.  
17  
 
 
1521 Handheld Thermometer Readout  
User’s Guide  
Ordering Information  
Cal Uncertainty and  
Repeatability  
Typical Drift  
(1 year)  
Model  
5626  
Type  
Range  
Size  
Pt-100 Ohm, 4-wire  
–200 to 660°C  
1/4” x 12” or 15”  
0.015°C  
0.03°C  
(6.35 x 305 or 381 mm)  
5628  
Pt-25 Ohm, 4-wire  
–200 to 660°C  
1/4” x 12” or 15”  
0.015°C  
0.03°C  
(6.35 x 305 or 381 mm)  
5614  
Pt-100 Ohm, 4-wire  
Pt-100 Ohm, 4-wire  
Pt-100 Ohm, 4-wire  
Pt-100 Ohm, 4-wire  
Pt-100 Ohm, 4-wire  
Pt-100 Ohm, 4-wire  
10K-ohm Thermistor  
10K-ohm Thermistor  
10K-ohm Thermistor  
10K-ohm Thermistor  
4K-ohm Thermistor  
–200 to 450°C  
–200 to 300°C  
–200 to 450°C  
–200 to 300°C  
–200 to 450°C  
–200 to 450°C  
0 to 110°C  
1/4” x 12” (6.35 x 305 mm)  
3/16” x 6” (4.76 x 152 mm)  
3/16” x 9” (4.76 x 229 mm)  
3/16” x 6” (4.76 x 152 mm)  
3/16” x 9” (4.76 x 229 mm)  
1/4” x 12” (6.35 x 305 mm)  
1/8” x 6” (3.2 x 152 mm)  
1/8” x 9” (3.2 x 229 mm)  
0.07” x 0.55” (1.8 x 14 mm)  
0.11” x 1.1” (2.8 x 28 mm)  
1/4” x 9” (6.35 x 229 mm)  
0.025°C  
0.025°C  
0.025°C  
0.035°C  
0.035°C  
0.035°C  
0.02°C  
0.01°C  
0.01°C  
0.01°C  
0.13°C  
0.13°C  
0.13°C  
0.01°C  
0.01°C  
0.01°C  
0.01°C  
0.005°C  
5613  
5612  
5627–6  
5627–9  
5627–12  
5610-6  
5610-9  
5611  
0 to 110°C  
0.02°C  
0 to 110°C  
0.02°C  
5611T  
5640  
0 to 110°C  
0.02°C  
0 to 60°C  
0.0015°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 ther-  
mometer. 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.  
18  
 
6 General Operation  
Battery  
6
General Operation  
This section explains the details of the operation of the 1521 with its compo-  
nents 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  
19  
 
 
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 nor-  
mally 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.  
2. 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 screw-  
driver. Place the screw in a safe place so it won’t get lost. Remove the  
battery cover to access the battery pack.  
3.  
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 direc-  
tion. Gently pull the battery plug off the connector.  
4. 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.  
5. Close the battery cover and replace the screw.  
6. 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 lo-  
cal 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  
20  
 
 
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.  
Function  
Action  
Power on  
Power off  
Backlight on  
Press the power button for at least two seconds when the power is off  
Press the power button momentarily (1/2 second or less) when the power is 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  
6.4  
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 dis-  
played 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 mini-  
mum 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 vari-  
ous 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 dis-  
charges 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 charac-  
teristics 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, includ-  
ing 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 resis-  
tance 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 dif-  
ferent 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).  
22  
 
 
6 General Operation  
INFO-CON Connector  
Temperature is generally sensed at the tip of the probe. To get an accurate tem-  
perature measurement the probe sheath should be well immersed, with ade-  
quate depth and fit, into the medium to be measured.  
CAUTION: Probes are fragile devices that can be easily damaged by me-  
chanical 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 pre-  
cautions:  
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 mea-  
sure temperature accurately. Generally, the probe will be purchased with the  
connector attached and programmed by the factory. Connectors can be pur-  
chased 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 at-  
taches 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-  
23  
 
 
1521 Handheld Thermometer Readout  
User’s Guide  
ognize that accuracy may be significantly degraded using a two-wire connec-  
tion because of wire resistance.  
GND  
C1  
P1  
GND  
C1  
P1  
GND  
C1  
C2  
P2  
C2  
P2  
C2  
P2  
P1  
Short  
Short  
J1  
J2  
J1  
J2  
J1  
J2  
Four-wire Connection  
Three-wire Connection  
Two-wire Connection  
Figure 6 Probe Wiring Diagrams  
24  
 
 
7 Display Functions  
7
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  
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.  
25  
 
 
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  
button  
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.  
26  
 
 
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 sim-  
plify 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 maxi-  
mum values setting them to the last measurement. Both the minimum and max-  
imum 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  
7.4  
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 but-  
tons 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.  
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 refer-  
ence 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.  
27  
 
 
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 with-  
out pressing ENT the unit remains unchanged. Once the unit is selected, subse-  
quent 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 be-  
tween 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 se-  
lect 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 de-  
crease 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 un-  
changed. 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 in-  
crease 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.  
28  
 
 
7 Display Functions  
CAL MODE  
7.8  
CAL MODE  
The calibration menu contains functions for setting probe and instrument cali-  
bration parameters. If a probe parameter is changed, the probe parameter is up-  
loaded 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 param-  
eters 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 be-  
fore the CAL Mode was entered.  
The functions contained in the CAL Mode are listed below in the order they ap-  
pear. In any of the functions the ENT button stores the displayed value or se-  
lection 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 func-  
tions 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  
7.8.2  
Mtr Due  
This function displays the date the 1521 is due for calibration. The date cannot  
be changed with this function.  
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  
7.8.4  
Time  
This function displays and sets the time of day. The time is always set, dis-  
played, 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.  
Passcode  
All functions below this function are protected by a pass-code so that only au-  
thorized users can access them. The passcode must be entered correctly to con-  
tinue. If the passcode is entered incorrectly or the MODE or CLR buttons are  
pressed, the message “Invalid Passcode” is displayed and the instrument is re-  
turned 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  
30  
 
 
7 Display Functions  
CAL MODE  
ensuring that it is not lost or forgotten. If necessary the passcode can be re-  
stored 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  
7.8.6  
Date  
This function displays the present date and allows it to be changed. This func-  
tion is placed in the passcode protected part of the CAL Mode since the calibra-  
tion 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 en-  
tered to save the changed values. The CLR button moves to the next function.  
Probe Lock  
This function locks or unlocks operation of the unit with the presently con-  
nected 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  
7.8.8  
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.  
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 mea-  
sured 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  
31  
 
 
1521 Handheld Thermometer Readout  
User’s Guide  
ITS-90  
IEC751  
CVD  
PRTs calibrated to ITS-90  
R(.01), a, b, c, d, a4, and b4  
none  
PRTs (RTDs) conforming to IEC-751  
PRTs characterized by the Callendar-Van Dusen  
equation  
R0, Alpha, Delta, and Beta  
YSI400  
THERM  
Thermistors matching the YSI-400 series  
none  
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 associ-  
ated 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 but-  
ton 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 Interna-  
tional 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 certifi-  
cate according to the following table.  
Unused coefficients must be set to 0.  
1521 Coefficients  
Certificate Value  
R(.01)  
Rtpw  
a
a5, a6, a7, a8, a9, a10, or a11  
b
b5, b6, b7, b8 or b9  
c
c6 or c7  
d
d
a4  
b4  
a4 or a5  
b4 or b5  
Consider the following examples.  
Example 1:  
32  
 
 
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)  
a
a8  
b8  
0.0  
0.0  
a4  
b4  
b
c
d
a4  
b4  
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.  
1521 Coefficients  
Certificate Value  
R(.01)  
R(273.16K)  
a
a5  
b5  
0.0  
0.0  
a5  
b5  
b
c
d
a4  
b4  
7.8.10  
7.8.11  
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 accu-  
racy (0.15°C to 4°C). There are no user programmable coefficients associated  
with this probe type.  
CVD  
The CVD (Callendar-Van-Dusen) type is used with PRTs that have unique cal-  
ibration 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
R 1 + α t δ  
1  
t 0  
t < 0  
0
100 100  
r(t[°C ]) =  
3
t
t
t
t
⎞ ⎛  
R 1 + α t δ  
1 β  
1  
⎟ ⎜  
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  
7.8.13  
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 as-  
sociated with this probe type. Temperature is converted from resistance based  
upon a standard YSI-400 table resident in the instrument.  
THERM  
The THERM thermistor type is for thermistors that have unique calibration co-  
efficients or do not match the YSI-400 specification. This type of probe gener-  
ally 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 + b1T1 + b2T2 + b3T3  
]
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  
b0  
b1  
b2  
b3  
a
b
c
d
34  
 
 
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:  
1521 Coefficients  
Certificate Value  
b0  
b1  
b2  
b3  
a
b
0.0  
c
7.8.14  
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 mea-  
surement 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  
7.8.16  
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 refer-  
ence. Use the Up and Down buttons to set each date segment and the ENT but-  
ton 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.  
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 regu-  
larly 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 fu-  
ture date. To set the date, use the Up and Down buttons to set each date seg-  
ment 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 func-  
tion 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 im-  
prove accuracy and resolution or decrease the time constant to reduce the re-  
sponse 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 but-  
tons 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  
7.8.19  
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.  
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.  
36  
 
 
8 Communications Interface  
RS-232 Connection  
8
Communications Interface  
Remote communications allows an external device, such as a computer, to com-  
municate 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 elec-  
trical interference, the serial cable should be shielded with low resistance be-  
tween 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  
5
GND  
9
GND  
RxD  
TxD  
4
3
2
1
8
7
6
TxD  
RxD  
Figure 8 RS-232 Wiring  
37  
 
 
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 car-  
riage 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  
Communication Command List  
8.2.1  
Primary Commands  
The following group of commands read or set various functions.  
Response  
Format  
Response  
Example  
Description  
Command  
Example  
t
Range  
Read measurement, extended  
format  
t[emperature]  
t: 999.999  
t: 125.745 C  
03-01-1999  
15:49:15  
{C, O, F, R, or K}  
mm-dd-yyyy  
hh:mm:ss  
Read measurement, simple format f[etch?]  
rea[d?]  
fetch?  
read?  
meas?  
t: 999.999  
{C, O, F, R, or K}  
t: 25.587 C  
me[asure?]  
Read minimum  
Read maximum  
m[inimum]  
min  
min: 999.999  
{C, O, F, R, or K}  
min: -14.653 C  
max: 416.781 C  
ma[ximum]  
max  
max: 999.999  
{C, O, F, R, or K}  
Clear minimum and maximum  
Read a hold register  
cl[ear]  
clear  
hld6  
h[ld]<n>  
hld<n>: 999.999 {C, O, F, hld6: 26.553 C  
R, or K}  
<n> can be 1 to  
6
 
8 Communications Interface  
Communication Command List  
Response  
Format  
Response  
Example  
Description  
Command  
re[solution]=n  
ti[me]  
Example  
res=1  
time  
Range  
1 to 3  
Set resolution digits  
Read time  
ti: hh:mm:ss  
ti: 16:23:45  
Set time  
ti[me]=hh:mm:s ti=08:15:0  
00:00:00 to  
23:59:59  
s
0
Note: You must set hours, min-  
utes, and seconds for the time to  
be set correctly.  
Read identification information  
*i[dn?]  
*idn?  
<manufacturer>,  
<model>,  
<serial number>,  
<firmware version>  
H2.a1r1t,  
1521,  
95001,  
Read model and firmware version  
Legend:  
*v[ersion]  
*ver  
ver.<model>,  
<firmware version>  
ver.1521,  
2.11  
[] 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 dis-  
abled 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  
Description  
Command  
Example  
Range  
Unprotect calibration parame-  
ters with the pass-code  
*pas[scode]=nnnnn  
*pas=12345  
Read date  
da[te]  
*pas  
date  
*pas  
da: yyyy-mm-dd  
ps:9  
da: 1999-03-28  
ps:0  
Read passcode protection  
state  
0 or 1  
Set date  
da[te]=yyyy-mm-dd  
da=1999-03-28  
1999-01-01 to  
2100-12-31  
Read probe serial number  
Set probe serial number  
se[rial]  
ser  
ser: xxxxxxxxxx  
ser: 100231A  
pr: ITS-90  
se[rial]=xxxxxxxxxx  
ser=001  
0 to 9, A to Z,  
., -, /  
Read probe type  
p[robe]  
pr  
pr: {ITS-90, IEC751,  
CVD, YSI400, THERM}  
39  
 
 
1521 Handheld Thermometer Readout  
User’s Guide  
Response  
Format  
Response  
Example  
Description  
Command  
Example  
pr  
Range  
Set probe type  
p[robe]=IT[S-90]/  
IE[C751]/ C[VD]/  
Y[SI400]/ T[HR]  
ITS-90,  
IEC751,  
CVD, YSI400,  
THERM  
Read ITS-90 R(.01) or CVD R0 r[0]  
r0  
r0: 9999.999  
r0: 100.035  
Set ITS-90 R(.01) or CVD R0  
Read ITS-90 coefficient  
r[0]=n  
r0=100.106  
a
1 to 900  
a/b/c/d/a4/b4  
{a/b/c/d/a4/b4}:  
-9.999999E-99  
a: -2.8644101E-5  
Set ITS-90 coefficient  
Read CVD coefficient  
Set CVD coefficient  
a/b/c/d/a4/b4=n  
a=-2.8644E-5  
al  
1.0 to 9.9e-18  
E+/-18  
al[pha]/de[lta]/be[ta]  
{al/de/be}: 9.99999999 al: 0.0038123  
al[pha]/de[lta]/be[ta]=n al=0.0038512  
Read THERM thermistor  
coefficient  
b0/b1/b2/b3  
b3  
{b0/b1/b2/b3}:  
9.999999e-99  
b3: -9.944070e-12  
Set THERM thermistor  
coefficient  
b0/b1/b2/b3=n  
b3=-9.944E-12  
E+/-18  
2,3,4  
Read probe wires  
wi[res]  
wi  
wi: 9  
wi: 4  
Set probe wires  
wi[res]=2/3/4  
pc[al]  
wi=4  
Read probe calibration date  
Set probe calibration date  
pcal  
pc: yyyy-mm-dd  
pc: 1999-03-28  
pc[al]=yyyy-mm-dd  
pc=1999-03-28  
1999-01-01 to  
2100-12-31  
Read probe due date  
Set probe due date  
pd[ue]  
pdue  
pd: yyyy-mm-dd  
pd: 1999-03-28  
pd[ue]=yyyy-mm-dd  
pd=1999-03-28  
1999-01-01 to  
2100-12-31  
Read filter  
fi[lter]  
fi[lter]=n  
*c1  
fi  
fi: 99.99999  
c1: 99.999  
c2: 9999.9  
fi: 0.5  
Set filter  
fi=0  
0.0 to 60.0  
Read low range calibration  
Set low range calibration  
Read high range calibration  
Set high range calibration  
*c1  
c1: -0.0121  
c2: -0.9  
*c1=n  
*c2  
*c1=-0.012  
*c2  
-1.999 to 1.999  
*c2=n  
*c2=-0.9  
-1980.0 to  
1980.0  
Read meter calibration date  
Set meter calibration date  
mc[al]  
mcal  
mc: yyyy-mm-dd  
md: yyyy-mm-dd  
mc: 1999-03-28  
: 1999-03-28  
mc[al]=yyyy-mm-dd  
mc=1999-03-28  
1999-01-01 to  
2100-12-31  
Read meter due date  
Set meter due date  
md[ue]  
mdue  
md[ue]=yyyy-mm-dd  
md=1999-03-28  
1999-01-01 to  
2100-12-31  
Legend:  
[] Optional Command data  
{} Returns either information  
40  
 
8 Communications Interface  
Communication Command List  
Response  
Format  
Response  
Example  
Description  
Command  
Example  
Range  
n Numeric data supplied by user  
9 Numeric data returned to user  
x Character data returned to user  
41  
 
9 Calibration  
Required Equipment  
9
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 pro-  
cedure 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).  
44  
 
10 Maintenance  
10  
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 re-  
sponsible 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 rec-  
ommended by Hart, users should check with an Authorized Service  
Center to be sure that the proposed method will not damage the equip-  
ment.  
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 equip-  
ment design, the operation of the thermometer may be impaired or safety  
hazards may arise.  
45  
 
 
11 Troubleshooting  
An Error Message Is Displayed  
11  
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 situa-  
tions 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 bat-  
tery drops below 0% and then automatically shuts itself off after dis-  
playing 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 pro-  
grammed 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”  
“Mtr cal expired”  
“Invalid Passcode”  
The probe calibration has expired. Have the probe calibrated and  
the calibration due date reset.  
The meter calibration has expired. Have the instrument calibrated  
and the calibration due date reset.  
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.  
47  
 
 
1521 Handheld Thermometer Readout  
User’s Guide  
Problem  
Solution  
While attempting to measure re-  
sistance the display shows an in-  
correct 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 wir-  
ing carefully (see Figure 6).  
Open, shorted, or damaged sensor or lead wires. Check the resis-  
tance across the sensor using a handheld DMM. Also check the resis-  
tance 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 in-  
sulation leakage.  
Stem conduction error. Make sure the stem of the probe is im-  
mersed 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 re-  
sulting in erratic readings. Try eliminating the source of interference or  
moving the 1521 to a different location. A well-grounded, shielded ca-  
ble 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 cor-  
rect 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 mem-  
ory testing.  
11.2  
CE Comments  
11.2.1  
EMC Directive  
Hart Scientific’s equipment has been tested to meet the European Electromag-  
netic Compatibility Directive (EMC Directive, 89/336/EEC). The Declaration  
of Conformity for your instrument lists the specific standards to which the unit  
was tested.  
48  
 
 
11 Troubleshooting  
CE Comments  
The instrument was designed specifically as a test and measuring device. Com-  
pliance 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 al-  
lows 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 sub-  
jected 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.  
49  
 
 

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