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Melting temperature of high temperature fixed points for thermocouple calibrations.

Pearce, J V; Montag, V; Lowe. D H,, ; Dong, W* (2011) Melting temperature of high temperature fixed points for thermocouple calibrations. Int. J. Thermophysics, 32 (1-2). pp. 463-470.

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Thermocouples can be calibrated at pure metal ingot-based fixed points at temperatures up to the freezing point of copper (1084.62 °C). For Pt/Pd thermocouples, the deviation function very often takes an approximately linear form up to the copper fixed point. The calibration of Pt/Pd thermocouples is therefore more amenable to extrapolation than that of Pt/Pt-Rh thermocouples. Here, the melting temperatures of one Co-C and one Pd-C eutectic fixed point are determined by extrapolating the deviation functions of several Pt/Pd thermocouples after the fashion of Edler et al. [1]. The results are compared with the melting temperatures measured using non-contact thermometry.

The uncertainty of the melting temperatures determined by extrapolation of the Pt/Pd thermocouple calibrations is ± 0.26 °C for the Co-C fixed point, and ± 0.36 °C for the Pd-C fixed point (both uncertainties for coverage factor k = 2). For both eutectic fixed points, these uncertainties are comparable to that of non-contact thermometry measurements. While a number of assumptions are made in performing the extrapolation of the calibrations that require further investigation, the method does appear to offer a useful complement to non-contact thermometry measurements.

[1] Melting Temperatures of Eutectic Fixed-Point Cells Usable for the Calibration of Contact Thermometers, F. Edler, P. Ederer, A.C. Baratto, H.D. Vieira, Int. J. Thermophys. (2007) 28:1983-1992

Item Type: Article
Keywords: Thermocouples, eutectic fixed points, fixed points, extrapolation, temperature assignment
Subjects: Engineering Measurements
Engineering Measurements > Thermal
Identification number/DOI: 10.1007/s10765-010-0892-8
Last Modified: 02 Feb 2018 13:14
URI: http://eprintspublications.npl.co.uk/id/eprint/4927

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