Realizing the redefined Kelvin : extending the life of ITS-90

Pearce, J. V. (author), Rusby, Richard (author), Veltcheva, R. I. (author), Campo, Dolores del (author), Garcia-Izquierdo, C. (author), Merlone, Andrea (author), Coppa, Graziano (author), Kowal, A. (author), Eusebio, L. (author), Bojkovski, Jovan (author), Žužek, Vincencij (author)

Following the redefinition of the kelvin, the user is presented with a more nuanced traceability route for temperature through the mise en pratique for the definition of the kelvin (MeP-K-19). Here we describe research to address several present and potential shortcomings with the current main dissemination route, namely the International Temperature Scale of 1990 (ITS-90). 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 it. Among these are the impact of the main types (1 and 3) of non-uniqueness which represent an important contribution to the uncertainties achievable with the ITS-90, and the possible need to identify an alternative to the mercury triple point, a key fixed point of the ITS-90 whose use could be banned by an international treaty. Significant progress has been made in addressing these problems through a) new determinations of Type 3 non-uniqueness which have been undertaken in the range –189 °C to 156 °C; b) a comprehensive evaluation of Type 1 non-uniqueness on a large number of Standard Platinum Resistance Thermometers (SPRTs) across multiple temperature regions; c) comparison of high temperature SPRTs in pressure-controlled heat pipes to characterize Type 3 non-uniqueness between 660.323 °C and 961.78 °C and d) new designs of ▫$CO_2$▫ and ▫$SF_6$▫ cells for use with long-stem SPRTs. The fixed-point cells have been improved compared to previous versions 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 has also been investigated.

• Language: English
• Keywords: kelvin, International Temperature Scale of 1990, standard platinum resistance thermometer, scale non-uniqueness, new temperature fixed-points
• Work type: Article
• Typology: 1.08 - Published Scientific Conference Contribution
• Organization: FE - Faculty of Electrical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2024
• Number of pages: 020002-1-020002-9
• Numbering: Vol. 3230, iss. 1, art. 020002
• PID: 20.500.12556/RUL-167928
• UDC: 621.317:006.91
• ISSN on article: 1551-7616
• DOI: 10.1063/5.0234458
• COBISS.SI-ID: 229648131
• Publication date in RUL: 20.03.2025

Record is a part of a journal

• Title: AIP conference proceedings
• Shortened title: AIP conf. proc.
• Publisher: American Institute of Physics
• ISSN: 1551-7616
• COBISS.SI-ID: 519457817

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: kelvin, Mednarodna temperaturna lestvica iz 1990, standardni platinasti uporovni termometer, neenakost lestvice, nove temperaturne fiksne točke

Projects

• Funder: Other - Other funder or multiple funders
• Funding programme: European Metrology Programme for Innovation and Research
• Project number: 18SIB02
• Name: Realising the redefined kelvin
• Acronym: Real-K