National Physical Laboratory

Calibration of digital indicators, iPRTs and thermocouples by comparison (-196 °C to +420 °C)

Comparison calibrations

Calibration of digital indicators and industrial platinum resistance thermometers

Industrial platinum resistance thermometers (IPRTs), and digital or analogue indicators with either resistance thermometer or thermocouple probes are widely used as temperature measurement devices in a variety of different applications. NPL provides a service for the calibration of these instruments. This service is UKAS accredited (laboratory number 0478) and ensures direct traceability to the International Temperature Scale of 1990 (ITS-90).

Calibrations against NPL standard thermometers can be carried out between -196 °C and +100 °C in appropriate liquid baths, and (for resistance sensors) in a dry-block calibrator between +50 °C and +420 °C.


The calibration uncertainty depends on a number of factors, including the resolution and temperature range for an indicator and the range and performance for an IPRT. The uncertainty is therefore assessed for each instrument at the time of calibration, but it can be as low as ±0.003 °C for liquid bath comparisons, and as low as ±0.037 °C for dry-block comparisons.

Calibration fees

The calibration fees depend on the required temperature range. They are therefore only available on request. Please contact us with your requirements.

Temperature Measurement and Calibration course

NPL runs a regular Temperature Measurement and Calibration course for technicians and technical managers requiring training in the practical aspects of temperature measurement, calibration and traceability. The course includes laboratory sessions covering realisation of ITS 90 fixed points, resistance thermometers, thermocouples and radiation thermometers. These laboratory sessions are supplemented by lectures in calibration techniques, uncertainties, traceability and accreditation.


Customer Services tel: +44 20 8943 6315

Last Updated: 1 Sep 2015
Created: 11 Sep 2007


Please note that the information will not be divulged to third parties, or used without your permission