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Fluke Calibration 1502A/1504 Thermometer Readouts

The 1502A and 1504 reference thermometers will read RTDs, PRDs, and thermistor sensors. Primary temperature standards, secondary temperature standards, fixed-point cells, water triple points, SPRTs, calibration baths, dry-block calibrators and temperature metrology training can also be found on this site.

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  • Best performance thermometers in their price range

    • Two Tweeners to choose from—reading PRTs or thermistors
    • Battery packs available
    • Best price/performance package

    One of Fluke Calibration’s best-selling products is the Tweener thermometer, and there’s a reason. No other company, not one, has a reference thermometer that comes close to the performance and features of the Tweener for anywhere near its price.

  • 1502A Tweener PRT Readout

    The 1502A Hart Scientific Tweener features accuracy up to ±0.006°C (the 1504 is even more accurate, up to ±0.002°C). In addition, it reads 100-ohm, 25-ohm, and 10-ohm probes, has a resolution of 0.001°C across its entire range, and is the smallest unit in its class. It also has an optional battery pack for completely portable operation.

    Each Tweener is programmable to match a probe's constants for maximum linearity and accuracy. All probe constants and coefficients are programmed through simple, front-panel keystrokes. Temperature is displayed in °C, °F, K, or resistance in ohms.

    The 1502A accurately measures the resistance of the probe and then converts the resistance to a temperature value using its built-in algorithms.

    For convenience, the 1502A reads the common industrial grade IEC-751 or "385 ALPHA RTD without any programming. Enter the actual R0 and ALPHA of the individual probe for increased accuracy. For maximum accuracy, use the ITS-90 formulas. The Tweener accepts the subranges 4 and 6 through 11.

    ITS-90 formulas reside in the Tweener's firmware. If your probe has been calibrated for any of the above subranges of the ITS-90, you simply enter the coefficients directly into your Tweener.

    Each thermometer comes complete with an RS-232 interface for automation of temperature data collection, calibrations, or process control functions. An IEEE-488 interface is available as an option.

    The 1502A is calibrated digitally using the front-panel buttons. You never have to open the box to calibrate it. This calibration protocol further reduces the cost of the 1502A. It goes where you go and works the way you want it to.

    1504 Tweener Thermistor Readout

    If you need more accuracy in a limited temperature range, the Model 1504 Tweener gives it to you as a thermistor readout. Thermistors are less fragile than PRTs and less likely to be impacted by mechanical shock. Thermistors are more sensitive to temperature, have faster response times, and come in many shapes for different applications.

    Typical accuracy of a 1504 is ±0.002°C with a resolution of 0.0001°C.


    With our 9934 LogWare, both Tweener models may be used for real-time data acquisition. Collect data and analyze it graphically or statistically. Additionally, Tweeners may be used as reference thermometers with our MET/TEMP II software.

    Battery pack

    Want to take your Tweener on the road? Order Fluke Calibration's 9320A Battery Pack. Our battery gives you 36 hours between charges, allowing you to take your work wherever you need.

    Calibration choices

    Each Tweener and its accompanying probe (sold separately) have their own individual calibration reports. Overall system error can be calculated from the individual errors, rendering the added cost of system data unnecessary. However, for those requiring it, system data is available at two or more temperatures of your choice. (See Calibration Model 1929-X )

  • Specifications 1502A 1504
    Temperature range1 −200°C to 962°C (−328°F to 1764°F) Any thermistor range
    Resistance range 0 W to 400 W, auto-ranging 0 W to 1 MW, auto-ranging
    Probe Nominal RTPW: 10 W to 100 W
    RTD, PRT, or SPRT
    Characterizations ITS-90 subranges 4, 6, 7, 8, 9, 10, and 11
    IPTS-68: R0, a, d, a4, and c4
    Callendar-Van Dusen: R0, a, d, and b
    Steinhart-Hart thermistor polynomial
    Callendar-Van Dusen: R0, a, d, and b
    Resistance accuracy
    (ppm of reading)
    0 W to 20 W: 0.0005 W
    20 W to 400 W: 25 ppm
    0 W to 5 KW: 0.5 W
    5 KW to 200 KW: 100 ppm
    200 KW to 1 MW: 300 ppm
    Temperature accuracy1 ±0.004°C at −100°C
    ±0.006°C at 0°C
    ±0.009°C at 100°C
    ±0.012°C at 200°C
    ±0.018°C at 400°C
    ±0.024°C at 600°C
    ±0.002°C at 0°C
    ±0.002°C at 25°C
    ±0.004°C at 50°C
    ±0.010°C at 75°C
    ±0.020°C at 100°C
    (Using 10 KW thermistor sensor, a=0.04. Does not include probe uncertainty or characterization errors.)
    Operating temperature range 16°C to 30°C 13°C to 33°C
    Resistance resolution 0 W to 20 W: 0.0001 W
    20 W to 400 W: 0.001 W
    0 W to 10 KW: 0.01 W
    10 KW to 100 KW: 0.1 W
    100 KW to 1 MW: 1 W
    Temperature resolution 0.001°C 0.0001°C
    Excitation current 0.5 and 1 mA, user selectable, 2 Hz 2 and 10 mA, automatically selected
    Measurement period 1 second
    Digital filter Exponential, 0 to 60 seconds time constant (user selectable)
    Probe connection 4-wire with shield, 5-pin DIN connector
    Communications RS-232 serial standard
    IEEE-488 (GPIB) optional
    Display 8-digit, 7-segment, yellow-green LED; 0.5-inch-high characters
    Power 115 V AC (±10%), 50/60 Hz, 1 A, nominal
    230 V AC (±10%), 50/60 Hz, 1 A, nominal, specify
    Size (H x W x D) 61 x 143 x 181 mm (2.4 x 5.6 x 7.1 in)
    Weight 1.0 kg (2.2 lb)
    Probes from Hart 5615, 5627, 5626, 5628, 5622 5640-44, 5610-65
    Calibration ISO 17025-accredited calibration provided
    1. Temperature ranges and accuracy may be limited by the sensor you use.
    • Models
      Model Name Description  
      Fluke 1502A Fluke Calibration 1502A Thermometer Readouts
      −200°C to 962°C (−328°F to 1764°F)
      Fluke 1504 Fluke Calibration 1504 Thermometer Readouts
      Any thermistor range