Measurement for our planet
Measurement for our planet

As COP26 approaches, discover how NPL plays a key role in enabling climate action through the delivery of accurate, reliable data that supports decision making and enables low carbon innovation.

Temperature and humidity measurements

Dew-point temperature in air

Range: -90 °C to +95 °C

Calibration of hygrometers against primary standards

Calibration against an NPL primary standard

+95 °C to +75 °C, best uncertainty ±0.12 °C to ±0.05 °C
+75 °C to +60 °C, best uncertainty ±0.05 °C to ±0.033 °C
+60 °C to -60 °C, best uncertainty ±0.033 °C
-60 °C to -75 °C, best uncertainty ±0.033 °C to ±0.10 °C
-75 °C to -90 °C, best uncertainty ±0.10 °C to ±0.50 °C

Calibrations are directly in terms of dew point in air (including frost point) or given in terms of related humidity quantities such as amount fraction, vapour pressure, vapour density and others.

Depending on the instrument type and the dew-point range, calibration is made by supplying a flow of gas to the instrument, or by locating the instrument in a humidity-controlled chamber or housing. Instruments with separate measuring head can be accommodated in a temperature-controlled chamber at above the dew-point temperature.

In addition, we offer calibration with larger uncertainty against a traceable reference, typically a condensation-principle hygrometer.

Calibration against a transfer standard
+95 °C to +82 °C, best uncertainty ±0.15 °C to ±0.1 °C
+82 °C to -50 °C, best uncertainty ±0.1 °C
-50 °C to -90 °C, best uncertainty ±0.1 °C to ±0.8 °C

Humidity calibrations are also available in non-air gases and at a range of pressures.

We can also carry out calibrations below -90 °C, and for other special requirements, please enquire.

Relative humidity calibration

Don’t see what you are looking for? Our diverse skill set enables us to provide bespoke solutions. Please contact us to discuss your requirements.

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Contact our Customer Services team on +44 20 8943 7070