Comparison of ITS-90 realizations from 13 K to 273 K between LNE-CNAM and INRIM

Since Key Comparison CCT-K2, only few comparisons on realizations of cryogenic fixed points have been carried out, be they bilateral (three, of which one still pending) or multilateral (two trilateral). Since a forthcoming general follow-up is unlikely, any bilateral comparison, not only key comparisons, is most welcome to provide evidence of the continuing thermometric capabilities of the laboratories involved in the realization of the ITS-90. Not too long after the creation in 2018 of the Joint Research Laboratory for Fluid Metrology Evangelista Torricelli between LNE-CNAM and INRIM, the two laboratories agreed to perform a bilateral comparison at all the cryogenic fixed points of the scale between 13 K and 273 K, including the two hydrogen vapour-pressure temperatures required for the full platinum resistance thermometer range 3.3.1 of the ITS-90. The results are reported here and show a substantial agreement, within the combined uncertainties.Comment: 20 pages, 3 figures, 3 table

Realizing the redefined kelvin: Extending the life of the ITS-90

Following the redefinition of the kelvin [1,2], the user is presented with a more nuanced traceability choice through the mise en pratique for the definition of the kelvin (MeP-K-19) [3]. Here we describe research to address several present and potential shortcomings with the current main dissemination route, namely using the International Temperature Scale of 1990 (ITS-90) [4]. The ITS-90 has served the global temperature measurement community well, providing reliable, low uncertainty traceability for over 30 years. However, there are some potentially life-limiting issues for the ITS-90. Among these are the impact of the main types (1 and 3) of non-uniqueness which currently limit the uncertainties achievable with the ITS-90, and the need to identify a possible alternative to the mercury triple point (a key fixed point of the ITS-90) whose use could be banned by an international treaty [5]. Progress in addressing these problems will be described through: • New determinations of Type 3 non-uniqueness have been undertaken in the range -189 °C to 156 °C; • A comprehensive evaluation of Type 1 non-uniqueness on a large number of Standard Platinum Resistance Thermometers (SPRTs) across multiple regions; • Comparison of high temperature SPRTs in pressure-controlled heat pipes to characterize Type 3 non-uniqueness between 660.323 °C and 961.78 °C; • New designs of CO2 and SF6 cells for use with long-stem SPRTs. These have been improved by using purer gases and more stable and uniform temperature-controlled baths, and by the development of a flexible set-up that can accommodate both capsule and long-stem SPRTs. The effect of replacing mercury on the ITS-90 interpolating equations and uncertainty propagation is also being investigated. References [1] https://www.bipm.org/en/publications/si-brochure [2] G. Machin, The kelvin redefined, Meas. Sci. Technol. 29 022001 (11pp) (2018) https://doi.org/10.1088/1361-6501/aa9ddb [3] B. Fellmuth, J. Fischer, G. Machin, S. Picard, P.P.M. Steur, O. Tamura, D.R. White, H. Yoon, The kelvin redefinition and its mise en pratique, Phil. Trans R. Soc. A., 374 (2064) (2016), p. 20150037, https://doi.org/10.1098/rsta.2015.0037 [4] Real-K project website: https://real-k.aalto.fi/ [5] The use of mercury, even for scientific purposes, could be severely restricted or even banned by international convention (UN Minamata Convention on Mercury which introduces controls over a myriad of products containing mercury)

2022 Update for the Differences Between Thermodynamic Temperature and ITS-90 Below 335 K

In 2011, a working group of the Consultative Committee for Thermometry published their best estimates of the differences between the thermodynamic temperature T and its approximation (T-90), the temperature according to the International Temperature Scale of 1990, ITS-90. These consensus estimates, in combination with measurements made in accordance with ITS-90, are an important alternative to primary thermometry for those requiring accurate measurements of thermodynamic temperature. Since 2011, there has been a change in the definition of the kelvin and significant improvements in primary thermometry. This paper updates the (T - T-90) estimates by combining and analyzing the data used for the 2011 estimates and data from more recent primary thermometry. The results of the analysis are presented as a 12th-order polynomial representing the updated consensus values for the differences and a sixth-order polynomial for their uncertainty estimates. (C) 2022 Author(s)

A new challenge for meteorological measurements: The meteoMet project-Metrology for meteorology

Climate change and its consequences require immediate actions in order to safeguard the environment and economy in Europe and in the rest of world. Aiming to enhance data reliability and reduce uncertainties in climate observations, a joint research project called MeteoMet-Metrology for Meteorology started in October 2011 coordinated by the Italian Istituto Nazionale di Ricerca Metrologica (INRiM). The project is focused on the traceability of measurements involved in climate change: surface and upper air measurements of temperature, pressure, humidity, wind speed and direction, solar irradiance and reciprocal influences between measurands. This project will provide the first definition at the European level of validated climate parameters with associated uncertainty budgets and novel criteria for interpretation of historical data series. The big challenge is the propagation of a metrological measurement perspective to meteorological observations. When such an approach will be adopted the requirement of reliable data and robust datasets over wide scales and long terms could be better met. © 2013 AIP Publishing LLC