Non-uniqueness and propagating uncertainties of the temperature scale realized using the triple point of sulfur hexafluoride

Abstract

The non-uniqueness of the temperature scale realized on the standard platinum resistance thermometer (SPRT) calibrated at the triple point of sulfur hexafluoride (TPSF6) has been evaluated, given that SF6 is a potential candidate for substitution of the triple point of mercury (TPHg) which is indispensable point for the ITS-90. Three SPRTs calibrated at the TPSF6 were compared with a reference thermometer from 14 K to 250 K using a precise measurement system for capsule type thermometers. The uncertainty of the temperature scale due to propagation of the uncertainties for calibrating the SPRTs was also evaluated. The results showed that the non-uniqueness of the temperature scale of the SPRTs calibrated at the TPSF6 was almost equivalent to that of the current ITS-90. This indicates that the TPSF6 possesses the capability for realization of a modified ITS-90 which is equivalent to the current ITS-90.

Keywords

• ITS-90
• Fixed point
• Triple point
• Temperature scale