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Fluke Calibration 1521 & 1522
Handheld Thermometer Readouts

  • Reads PRTs/RTDs to ±0.025°C and thermistors to ±0.005°C
  • Model 1522 stores multiple data sets totaling 10,000 readings
  • INFO-CON connector allows interchangeable use of calibrated probes
  • INFO-CON eliminates errors from programming probe data

With the Super-Thermometer, Black Stack, and Tweener thermometers, Hart established itself as the clear product leader for thermometer readouts. Hart's pattern of offering more power and more versatility for less money is indisputable.  Another case in point: Hart offers the two most powerful handheld thermometers in the world.

    Fluke Calibration 1521 & 1522 Handheld Thermometer ReadoutsClick for larger image
1521 & 1522 Shown
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1521 and 1522 are the first standards thermometers to fit into a battery-powered handheld package. They're as accurate as ±0.005°C!  You'll only find this level of accuracy in large desktop units that cost three times more.  It's no wonder Hart calls the 1521 the Little Lord Kelvin of thermometry.

Fitting easily into your hand and weighing only 1 pound (0.4 kg), these thermometers can go anywhere.  And when they get there, you can have total confidence in the accuracy of your measurements.  1522 has the power of a full data logger, with memory to hold 10,000 readings.


1521 and 1522 read both Pt-25 and Pt-100 RTDs as well as thermistors.

PRTs and RTDs, with their wide temperature ranges and stabilities, have long been favored as temperature standards. From -200°C to 100°C, the 1521 reads PRTs accurately to ±0.025°C. Even at 800°C these are high-precision readouts, accurate to ±0.1°C.

Ultra-stable thermistors offer excellent stability and even greater accuracies over a more narrow range-typically from about -10°C to 110°C. At temperatures below 50°C, these Handheld Thermometers read thermistors to ±0.005°C. Accuracy at 100°C is ±0.02°C.

While a small number of handheld thermometers on the market offer 0.01° resolution, they fail to provide the accuracy necessary for the last digit to be meaningful. Hart's Handheld Thermometers let you select resolution from 0.1° to 0.001° and offer the accuracy to support even 0.001° resolution.

Of course, the 1521 and 1522 let you match the exact resistance-versus-temperature characteristics of an individually calibrated probe. This is true standards thermometry. Hart's Handheld Thermometers read ITS-90, Callendar-Van Dusen, or Steinhart-Hart coefficients for maximum system accuracy. These are real algorithms, not approximating conversion methods or electronic look-up tables. If you want to use common industrial curves, RTDs can be read using the common DIN 43760 (IEC 751) curve and thermistors can be read using the YSI 400 curve.

INFO-CON Connectors

Probes attach to the 1521 and 1522 using Hart's own "INFO-CON" connector. The INFO-CON (partially based on U.S. Patent 5,857,777) allows you to change the probes you use without requiring you to reprogram your readout. A memory chip in the INFO-CON stores all the critical information about your probe, including its serial number, recall date, and calibration constants.

When you connect your probe, the 1521 automatically recognizes whether you're using an RTD or thermistor and downloads the calibration constants and type of conversion specific to your probe. It also checks the recall date stored in the INFO-CON to verify it has not expired. To dedicate a single probe to your readout, disable the password-protected interchangeability function and your thermometer will read only the probe you specify.

Forget entering calibration constants yourself, and don't worry about the mistakes that can so easily occur during that process. You don't even need to select your sensor type. It's all stored in the INFO-CON. Just plug in your probe and you're ready to take readings. It doesn't get any easier.

Information is loaded into the memory of the INFO-CON by Hart when you purchase a probe or have a probe recalibrated by Hart. Alternatively, you may load your own information into an INFO-CON through the Handheld Thermometer or through Model 9934 LogWare.

If you'd like to use a Hart Handheld Thermometer with probes you already own, no problem! Spare connectors are available. They easily connect to your probes, and you can program them yourself.

Model 1521 Little Lord Kelvin

The 1521 Little Lord Kelvin uses a menu system for convenient access to all functions. Calibration and sensor programming functions are password protected to help prevent unauthorized access.

"Min" and "Max" functions store the lowest and highest readings since the last reset. The "Hold" function freezes and stores the current reading (up to six may be stored) for later recall. And the "Delta" function computes the difference between the current reading and a reference value, which may be recorded at any time.

Each thermometer comes complete with rechargeable nickel-metal-hydride batteries, an AC adapter/charger, an RS-232 cable for connecting to your PC, and a spare INFO-CON connector. Every unit also includes a NIST-traceable calibration with actual resistance measurements for your individual meter at ten points-four representing typical RTD values and six representing typical thermistor values.

A wide variety of standards-quality probes are available from Hart in many different shapes, sizes, and price ranges. Hart offers PRTs as accurate as ±0.010°C and thermistors as accurate as ±0.001°C. The uncertainty of your probe should be added to the uncertainty of the meter to compute total system uncertainty.

Model 1522 Little Lord Logger

The Model 1522 Little Lord Logger has all the power and great features of the 1521 plus the ability to log data. Two data acquisition modes are included.

In "Auto Logging" mode, the 1522 can store up to 10,000 measurements at user-selected intervals, including the value, unit of measure, date, and time of each measurement. If you need more than one data set, stop recording any time and record as many sets as you like up to a total of 10,000 values. Once the 10,000 value limit is reached, recording stops, so data is never lost unless you tell the 1522 to clear its log.

The 1522 also holds as many as 25 data labels in its memory so that each set of data can be uniquely tagged. Simply select one of the 25 labels you've created before recording data. This label is then recorded with each measurement.

In "Demand Logging" mode, up to 100 individual measurements can be recorded, each one tagged with one of the 25 data labels. Whether you need a lot of measurements from one source or single measurements from many sources, the 1522 is a powerful data recording tool.

With Hart's 9934 LogWare software, data management is easy. Data sets gathered remotely through the 1522 can be easily downloaded to a PC either as a single file or as individual files for each data set. Link the LLL to your PC through a serial cable to send data as ASCII or binary files. View the data, graph it, or apply alarms. With LogWare you can record data in real time either from a 1522 or 1521 Thermometer.

One company consistently delivers powerful metrology products that make your life easier. Ask other companies about their handheld thermometers. Ask them about their thermometers that are accurate to within a few millikelvin and that record data at the touch of a button. Then ask them to give it all to you in one package. Fluke Calibration does-at a price you'll love. Call us today and get the most powerful handheld thermometers in the world.

Sensor Type  Pt 25 to Pt 100  Thermistor 
Temperature Range  -200°C to 962°C  -50°C to 150°C 
Resistance Range  0W to 400W  0W to 500 KW 
Characterizations  ITS-90, IEC-751 (DIN "385"), Callendar-Van Dusen  Steinhart-Hart thermistor polynomial, YSI 400 (2252 ohms) 
Temperature Accuracy (meter only)  -200°C to 100°C: ±0.025°C 
100°C to 400°C: ±0.05°C 
400°C to 800°C: ±0.1°C 
800°C to 962°C: ±0.15°C 
0°C to 50°C: ±0.005°C 
50°C to 75°C: ±0.01°C 
75°C to 100°C: ±0.02°C 
Excitation Current  0.5 mA  5 mA 
Operating Range  0°C to 40°C 
Temperature Resolution  0.001° 
Measurement Period  1 second 
Digital Filter  1- to 60-second exponential filter 
Probe Connection  INFO-CON Connector 
Communications  RS-232 
Memory  Stores 6 readings in "Hold" mode  Logs 10,000 readings in "Auto Logging" mode; logs 100 readings in "Demand Logging" mode. Memory holds up to 25 data labels that may be attached to Demand Log readings or Auto Log data sets. 
Display  6-digit, 7-segment LCD with 16x1 alphanumeric 
Power  Rechargeable nickel-metal-hydride batteries (AC adapter included) 
Size (HxWxD)  20 x 11 x 4 cm (7.75 x 4.2 x 1.5 in) 
Weight  0.4 kg (1 lb.) 
Calibration  Accredited 10-point, NIST-traceable resistance calibration provided 
Ordering Information
Model Description Buy Online Price
1521 Fluke Hart 1521-156 Handheld Thermometer, 1 Channel Discontinued
Optional Accessories
MFR ID: 1658744
Fluke Calibration 9934-S LogWare Software, 1-chan, Single User Buy Now Sale $346.50
(Reg. $385.00)
MFR ID: 1658732
Fluke Calibration 9934-M LogWare Software, 1-chan, Multi User Buy Now Sale $657.00
(Reg. $730.00)
MFR ID: 1650431
Fluke Calibration 2370 RS-232 Cable for 1521/1522/1620 Buy Now Sale $67.50
(Reg. $75.00)
MFR ID: 1650446
Fluke Calibration 2371 Connector, INFO-CON Buy Now Sale $108.00
(Reg. $120.00)
9318 Fluke Hart 9318 Case, 1521/1522 & Probe Carrying (Discontinued) Buy Now
MFR ID: 1650896
Fluke Calibration 2601 Probe Carrying Case Buy Now Sale $126.00
(Reg. $140.00)
MFR ID: 1650740
Fluke Calibration 2521 Battery, for 1521 or 1522 Thermometer Discontinued
2361 Fluke Hart 2361-156 Adapter, Spare AC, 12V, 110V Discontinued