Contact thermometry at NPL: a journey from the argon triple point to the iridium-carbon eutectic point in the context of UK industry needs

Jonathan Pearce, Temperature & Humidity group, Engineering Measurement Division

Contact thermometry is temperature measurement using sensors in contact with the medium to be measured. They are generally either resistance thermometers or thermocouples.

NPL’s primary realisation and dissemination of the International Temperature Scale of 1990 between the triple point of argon (83.8058 K) and the freezing point of silver (961.78 °C) is by means of standard platinum resistance thermometers (SPRTs) and very pure fixed-point cells. These devices provide the basis of traceability of temperature measurements in the UK in this temperature range.