Temperature difference thermometer
Pt100 Model D
(-100 °C … 250 °C)

Temperature difference thermometer for measuring vertical temperature gradients and precise temperature measurement.

  • Temperature range: -100 °C to 250 °C
  • small measurement uncertainties: 6 mK to 11 mK
  • Measurement of vertical temperature gradients
  • Temperature standard and temperature difference thermometer

The thermometer for temperature differential measurement is a practical tool for daily laboratory work. The thermometer makes work easier for:

  • Measuring of vertical temperature gradients
    Vertical temperature gradients must be measured as part of the measurement uncertainty of a calibration (e.g. according to DKD-R 5-4 “Calibration of block calibrators”, DKD-R 5-3 “Calibration of thermocouples” or DKD-R 5-1 “Calibration of resistance thermometers”).
  • Optimising of calibration furnaces
    When optimising heating zones on calibration furnaces, such as the 3-zone high-temperature calibration furnace or the Medusa calibration furnace, precise temperature differences must be measured.
  • Precise temperature standard
    The main measuring point of the differential thermometer is identical to the design of the eXacal PT 100 M and can be calibrated with the same measurement uncertainties. This means that the differential thermometer can be used not only for measuring temperature differences but also as a temperature standard.

The differential thermometer has two Pt 100 temperature sensors positioned at the bottom of the thermometer and at a distance of 4 cm. 

Schematic representation of the differential thermometer

Uncertainty of Measurement

eXacal thermometers can be calibrated in our own DAkkS calibration laboratory. The DAkkS accreditation ensures that all calibrations are traceable to national and international standards.

The calibration of the eXacal resistance thermometers is made at ITS-90 fixed points. It is also possible to make calibrations according to the comparison method in calibration baths and calibration furnaces. The measurement uncertainty is calculated from many components. The largest contributions are reproducibility, ITS-90 characteristic, self-heating and hysteresis.

With the differential thermometer, the main measuring point is calibrated at fixed temperature points. The second measuring point is measured by a differential measurement at maximum immersion depth in a heat pipe with an extremely good vertical profile.

  • Small Measurement uncertainties with DAkkS calibration certificate
  • Temperature fixed points from mercury -38,8344 °C to tin solidification point 231,928 °C
  • Differential measurement in a heat pipe / heat pipe furnace

Bereich Verfahren Messunsicherheit
-38,8344 °C Mercury triple point 6 mK
0,01 °C Water triple point 6 mK
29,7646 °C Gallium melting point 6 mK
156,5985 °C Indium melting point 10 mK
231,928 °C Tin solidification point 11 mK

The measurement uncertainties given are k=2, include an ITS-90 characteristic curve and are specified for the corresponding range.


Model eXacal Pt100 D
Temperature range  -100 °C bis 250 °C
Nominal resistance  Pt100 (100 Ohm)
typical annual drift  2,5 mk
Connection type  four-wire
Connection  Banana plugs or depending on configuration
Sheath material  metal
Handle  ∅ 20 mm x 100 mm
Diameter  6 mm
Length  400 mm
Connection Cable  2 m
Measuring resistors / Temperature sensors
R0  100 Ohm ± 0,05 Ohm (High-Temperature Measuring resistors)
Alpha  0,003850 ± 0,000005
Norm  IEC 60751:2008
Length  6 mm
Recommended measuring current  1 mA
Self heating  30 mK @ 1 mA
 at 29,7646 °C (Gallium-meltingpoint)
Calibration (Main measuring point)
Fixed point calibration  6 mK bis 11 mK
Comparison calibration  10 mK bis 25 mK


Questions about Thermometers?