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The method of instantaneous comparisons applied to the calibration of SPRTs in liquid nitrogen and liquid argon.

Rusby, R L; Sutton, G J M; Stanger, L R; Veltcheva, R I (2014) The method of instantaneous comparisons applied to the calibration of SPRTs in liquid nitrogen and liquid argon. Int. J. Thermophysics, 35 (3). pp. 657-667.

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Abstract

Temperature drift is one of the most significant sources of uncertainty in the calibration of thermometers by comparison. For similar thermometers, measuring the resistances by ratio to the resistance of a reference thermometer, rather than to a fixed standard resistor, allows the effect of drift to be overcome. The ratios, R1 / Rref, etc, are substantially independent of temperature, so the exact value of Rref is not important: all that matters to establish the calibration is that R1 / Rref, etc, are measured accurately, and that the adopted value of Rref is accurately related to temperature. This paper describes the method and gives results of its application in liquid nitrogen and liquid argon, with repeatabilities of < ~0.1 mK. The method is not new, but it appears not to have been widely used or discussed in the literature. It has potential for application in all comparisons of like thermometers, in liquid baths, metal blocks and furnaces, as well as in testing the temperature uniformity of the baths, etc, and in investigations such as into thermometer stability or hysteresis. Some comparisons in conditions of rapid drift are also presented.

Item Type: Article
Keywords: Comparison calibration, dynamic response, liquid argon, liquid nitrogen, platinum resistance thermometer
Subjects: Engineering Measurements
Engineering Measurements > Thermal
Identification number/DOI: 10.1007/s10765-014-1631-3
Last Modified: 02 Feb 2018 13:14
URI: http://eprintspublications.npl.co.uk/id/eprint/6274

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