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 -180 °C to -80 °C and at the fixed temperatures at -189 °C and
-196 °C.

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.