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Experiences in calibrating industrial platinum resistance sensors between-196 °C and 80 °C

Veltcheva, R I; Rusby, R L; Peters, D M; Watkins, R E J (2018) Experiences in calibrating industrial platinum resistance sensors between-196 °C and 80 °C. International Journal of Thermophysics, 39 (5). 65

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Recently a requirement arose to provide sensors for measuring the temperature of a substantial reference black-body cavity to operate in vacuum over a temperature range from - 100 °C to 80 °C (~170 K to ~350 K), with an additional capability to operate at ~ -170 °C (~100 K) as a point of near zero radiance. The main radiating surface is a black aluminium-alloy plate, with concentric V-grooves, 444 mm in diameter and 97 mm thick, whose temperature will be measured using a small (capsule-type) Standard Platinum Resistance Thermometer with an uncertainty of ~0.002 °C. Several additional sensors are required for control purposes and to establish the temperature uniformity of the black-body structure and its surrounding aluminium-alloy isothermal shield. These sensors should remain stable within the uncertainties of 0.03 °C (k = 3) ideally for 20 years. This paper discusses the testing and calibration of two types of industrial Pt100 platinum resistor, which were selected for this purpose. It discusses temperature cycling and calibration, the interchangeability of the sensors from a given batch, and the methods of interpolation over the temperature range. It is concluded that the sensors can meet the requirements provided that they have been individually tested, and that there is a degree of redundancy so that long-term changes can be detected. The calibration data could be fitted by cubic or quartic equations expressing temperature as a function of resistance (or resistance ratio), this being simpler than the ITS-90 formulation and more convenient than using the (technically obsolete) Callendar-Van Dusen equation.

Item Type: Article
Keywords: industrial PRT, calibration, iterpolation equations
Subjects: Engineering Measurements > Thermal
Divisions: Engineering, Materials & Electrical Science
Identification number/DOI: 10.1007/s10765-018-2386-z
Last Modified: 19 Jun 2018 14:18
URI: http://eprintspublications.npl.co.uk/id/eprint/7961

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