Thermometer calibration at low temperatures


Thermometer calibration at low temperatures

 

You want to calibrate thermometers at extremely low temperatures? But the temperature range of the calibration baths and standardised procedures used is not enough for you? Then you are at the right place. We use boiling nitrogen to extend the temperature range. 

With the three calibration methods shown here, you can calibrate thermometers in the temperature range from -80 °C to -180 °C and at the fixed temperatures at -189 °C and -196 °C.


Ar

-189 °C

ITS-90 Calibration
to the triple point
of argon

 

 

LN2

-196 °C

Thermometer calibration with
liquid nitrogen as reference temperature

 

 

-80 °C to -180 °C

Thermometer calibration with
selectable calibration points in the nitrogen cryostat

 

 

With the boiling nitrogen we can:

  • Calibrate thermocouples and resistance thermometers in the nitrogen cryostat with freely selectable calibration temperatures between -80 °C and -180 °C.
  • use the boiling point of nitrogen and calibrate thermometers at -196 °C.
  • use the argon triple point at -189.3442 °C and perform a complete ITS-90 calibration in the temperature range from 0 °C to -189 °C.
    The fixed points used are: 

    • Water triple point 0.01 °C
    • Mercury triple point -38.8344 °C
    • Argon triple point -189.3442 °C

Technical background

The calibration of thermometers at extremely low temperatures is a technical challenge. Conventionally, calibration baths or temperature dry block calibrators are used to calibrate thermometers in the negative temperature range. However, these quickly reach their limits when it comes to cooling and are only used down to approx. -80 °C.

Calibration baths are cooled with compressors. For stable control of the calibration temperature, an electric heater works “against” the compressor, which always cools at maximum power. In addition, the calibration media used (such as silicone or ethanol) change their viscosity very strongly and absorb water from the ambient humidity. Both complicate the temperature control of the calibration baths. The lowest temperature that calibration baths with stable control can reach is about -80 °C. 

Temperature dry block calibrators are cooled with Peltier elements or sterling motors. These technologies are limited and can be used down to approx. -50 °C with Peltier elements or -100 °C with sterling motors.

To overcome these limitations, we use liquid nitrogen as a “cold source”. This enables us to extend the temperature range up to -196 °C when calibrating thermometers.

 

 

 

 

New digital archive Klasmeier Cloud: Calibration documents quickly and easily available

The new Klasmeier Cloud – the perfect archive for all calibration documents. From now on, our customers will find a QR code on all devices calibrated by Klasmeier, with which they can quickly and easily access our digital archive. Especially useful: In addition to all calibration documents, the contact details of the relevant contact person at Klasmeier are also always available there. So even five or more years from now, if you have any questions about your calibration product, you can find the information you need with just one click.

 

Questions about calibration?

Contact: Boris Kalb – b.kalb@klasmeier.com