Determination of non-uniqueness of the ITS-90 in the range between the aluminium and silver freezing points

Project Description

The non-uniqueness of the ITS-90 between 660 °C and 962 °C will be assessed by comparing within this intercal several high temperature standard platinum resistance thermometers (HTSPRT's) calibrated at the fixed points of the ITS-90. The comparison will be performed at IMGC using a pressure controlled sodium heat-pipe. This device allows temperature uniformity and stability at the millikelvin level to be obtained in the whole range of operation. The accuracy in the comparison is expected to be within ±2 mK, thus it is suitable to provide meaningful data on non uniqueness.

An appreciable number of HTSPRT's, namely, from 25 to 30 units, will be investigated. The thermometers, of different types and from different manufacturers, will be supplied by all the participating laboratories.

Further Information

Two non-EUROMET laboratories, namely, NIST (USA) and NIM (PR China) will cooperate in the project. Nist will provide some 15 HTSPRT's and a scientist form NIM will take part in the measurements at IMGC.