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Zinc-bismuth and aluminium-indium monotectic alloy-based fixed-point cells with double phase transition for in-situ calibration of thermocouples.

Lowe, D H B; Kodwani, D* (2015) Zinc-bismuth and aluminium-indium monotectic alloy-based fixed-point cells with double phase transition for in-situ calibration of thermocouples. Int. J. Thermophysics, 36 (10-11). pp. 2654-2665.

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Abstract

Re-calibration of a thermocouple after it has been installed in a process is often not practical. In-situ monitoring of performance is desirable and can be done with built in reference standards based on melting or freezing phase transitions. Monotectic alloys frequently have two invariant melt/freeze phase transitions taking place in the same material over a range of compositions. This makes them potentially well suited to be in-situ temperature calibration artifacts, able to correct for thermocouple drift without the need to disturb the thermocouple. A zinc-bismuth fixed point was constructed and has been shown to be stable with two well defined melting plateaus at nominally 255 \celsius\ and 415 \celsius. Two miniature fixed points based on Bi-Zn and In-Al alloys and designed to be permanently installed with a thermocouple were made. Measurements showed that the phase transitions could be identified despite the small quantity of metals used. The alloys were sufficiently stable to have the potential to provide improved long term confidence in process control and monitoring.

Item Type: Article
Subjects: Engineering Measurements
Engineering Measurements > Thermal
Identification number/DOI: 10.1007/s10765-015-1940-1
Last Modified: 02 Feb 2018 13:13
URI: http://eprintspublications.npl.co.uk/id/eprint/6921

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