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Challenging calculations in practical, traceable contact thermometry

Pearce, J V; Rusby, R L (2018) Challenging calculations in practical, traceable contact thermometry. In: Advanced Mathematical and Computational Tools in Metrology and Testing XI. World Scientific Publishing, pp. 257-264. ISBN 9789813274297

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Almost every technological process depends in some way on temperature measurement and control; for example, reliable electricity, intercontinental flights, and fresh food. They all depend on a sophisticated measurement infrastructure that allows temperature measurements to be traced back to the SI unit of temperature, the kelvin, via the International Temperature Scale of 1990 (ITS-90). In most cases it is not practical to measure temperature directly, so practical thermometers generally measure some temperature-dependent property such as resistivity or the thermoelectric effect. A temperature scale has two components: defined temperature values associated with a set of highly reproducible `fixed points', which are states of matter such as phase transitions (freezing, melting or triple points of pure substances), and specified interpolating instruments with defined interpolating or extrapolating equations. Both the thermometers and the fixed points exhibit surprisingly rich physics, a good command of which is, in many cases, at the limit of current knowledge and capabilities. Some topical examples are: calculation of phase diagrams of binary alloys in the limit of low solute concentration for reducing uncertainty in the dissemination of the International Temperature Scale of 1990; calculation of the effect of impurities and crystal defects on the resistivity of platinum wires of Standard Platinum Resistance Thermometers; calculation of Seebeck coefficients of metals to improve characterization of thermocouple behaviour; calculation of the vapour pressure of noble metals and their oxides to improve characterization of thermocouple calibration drift; development of algorithms for handling and analyzing very large data streams arising from a practical primary thermometry based on the measurement of Johnson noise. This paper presents the state of the art in these topics, as well as their background and how they relate to real-world problems. It will outline areas where further progress is required, and how the mathematics and computational metrology community may be able to contribute.

Item Type: Book Chapter/Section
Subjects: Engineering Measurements > Thermal
Divisions: Thermal & Radiometric Metrology
Publisher: World Scientific Publishing
Last Modified: 27 Nov 2020 15:13
URI: http://eprintspublications.npl.co.uk/id/eprint/9000

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