WP 3: Assessment of traceability and dissemination of thermodynamic temperature

CEM (WP leader), CMI, CNAM, INRiM, INTiBS, LNE, NPL, PTB, TIPC-CAS, TUBITAK, UL

The aim of this work package is to develop a coherent framework to ensure consistency of the dissemination of temperature from several NMIs over the range 4 K to 300 K whether it is by thermodynamic temperature or the defined scale, i.e. the International Temperature Scale of 1990 (ITS-90). This framework will be recognised internationally through being a recommendation to CCT about the measurement uncertainties and the level of equivalence between these approaches to ensure that users globally have a clear understanding of the relationship between the two approaches.

The dissemination of calibrated cSPRTs to multiple NMIs will ensure that, upon accounting for the consensus estimate of the differences (T–T₉₀), the realizations of T and T₉₀ are mutually consistent within their combined uncertainties, and will assess the uncertainty of each scale both in correspondence of the fixed points of ITS-90 and in the intermediate ranges between fixed points, where the uncertainty of ITS-90 is limited by various non-uniqueness contributions. The final outcome of these comparisons will inform the CCT with regard to the uncertainty which may be achieved by thermodynamic calibrations with different primary methods and will inform a future revision of the mise en pratique for the definition of the kelvin.