Standard platinum resistance thermometer interpolations in a revised temperature scale

Abstract

The thermal metrology community is considering revising the International Temperature Scale of 1990 (ITS-90), motivated by the opportunity to improve the thermodynamic accuracy, reproducibility, and ease of use of the scale, as well as health and safety concerns with the use of mercury in the current scale. This paper considers the mathematical structure of the standard platinum resistance thermometer (SPRT) interpolations of the ITS-90 and identifies (i) mathematical features that are advantageous and should be retained, (ii) opportunities for improvements, and (iii) the research required to maximise the benefits from such improvements. The improvements considered include minor adjustments that leave ITS-90 intact, numerical adjustments to reference resistance ratios that preserve the structure of ITS-90, fixed-point replacements, new subranges, and large-scale changes in the mathematical structure of the interpolations. A significant research effort will be required to implement some of the changes. Overall, an improvement in the thermodynamic accuracy by a factor of about ten is relatively easily realised, but improvements in reproducibility of the scale of even a couple of tens of percent will be hard won. For most users, the costs and inconvenience of a substantial scale revision may outweigh the benefits.

Towards Realising the Redefined Kelvin

“…This means the community has time to work on all these approaches and debate which is most appropriate for the user community. If a future scale is required much of the framework is in place to facilitate its introduction [67]. However, it must be kept in mind that the potential cost of introducing a new scale needs to be seriously considered, as does the potential disruption to users.…”

Design and Development of a Low Cost, Non-Contact Infrared Thermometer with Range Compensation

“…While contact type thermometers are recommended over non-contact types, it is not widely adopted since IR thermometers have greater sensitivity and specificity over contact temporal thermometers for temperatures >37.5 • C [37]. In working towards commercial use, it may be useful to use a second order equation for compensation adjustments from our two first-order equations, as well as to bear in mind the potential revisions on the International Temperature Scale of 1990 (ITS-90) for better reproducibility [38], along with the use of smart materials to make the thermometer casings [39].…”

Design and Development of a Low Cost, Non-Contact Infrared Thermometer with Range Compensation

“…While contact type thermometers are recommended over non-contact types, it is not widely adopted because IR thermometers have greater sensitivity and specificity over contact temporal thermometers for temperatures >37.5 °C [38] . In working towards commercial use, it may be useful to use a second order equation for compensation adjustment from our two first-order equations as well as bearing in mind potential revisions on the International Temperature Scale of 1990 (ITS-90) for better reproducibility [39] along with the use of smart materials to make the thermometer casings [40].…”