Evaluation of the temperature scale of SPRT calibrated at the triple point of sulfur hexafluoride

Abstract We evaluated the non-uniqueness of the temperature scale of the standard platinum resistance thermometer (SPRT) calibrated at the tripe point of sulfur hexafluoride (TPSF6), which is one of the candidates for the substitute of the triple point of mercury (TPHg). Three SPRTs calibrated at the TPSF6 were compared with a reference thermometer from 14 K to 250 K by using a precise comparison system for capsule type of thermometers. The uncertainty of the temperature scales from propagation of the uncertainties for calibrating SPRT was also evaluated. The result shows that the non-uniqueness of the temperature scale of the SPRT calibrated at the TPSF6 was almost equivalent to that of the ITS-90. This means that the triple point of TPSF6 possessed a capability for realization of the temperature scale which was equivalent to the ITS-90.