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A comprehensive survey of thermoelectric homogeneity of commonly used thermocouple types

Machin, J; Tucker, D; Pearce, J V (2018) A comprehensive survey of thermoelectric homogeneity of commonly used thermocouple types. Measurement Science and Technology, 29 (6). 067002

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Abstract

Thermocouples are widely used as temperature sensors in industry. The electromotive force (emf) generated by a thermocouple is produced in a temperature gradient and not at the thermocouple tip. This means that the thermoelectric inhomogeneity represents one of the most important contributions to the overall measurement uncertainty associated with thermocouples. To characterise this effect, and to provide some general recommendations concerning the magnitude of this contribution to use when formulating uncertainty analyses, a comprehensive literature survey has been performed. In the case of Type K and N thermocouples, the survey has been augmented by a substantial amount of data based on calibrations of mineral insulated, metal sheathed thermocouple cable reels from thermocouple manufacturers. Some general conclusions are drawn and outline recommendations are given concerning typical values for the uncertainty arising from thermoelectric inhomogeneity for the most widely used thermocouple types in the as-new state. It is stressed that these recommendations should only be heeded when individual homogeneity measurements are not possible. It is also stressed that the homogeneity can deteriorate rapidly during use, particularly for base metal thermocouples.

Item Type: Article
Subjects: Engineering Measurements > Thermal
Divisions: Engineering, Materials & Electrical Science
Identification number/DOI: 10.1088/1361-6501/aabaa3
Last Modified: 14 Jun 2018 13:13
URI: http://eprintspublications.npl.co.uk/id/eprint/7940

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