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The development of a practical, drift free, Johnson-noise thermometer for industrial applications.

Bramley, P*; Cruickshank, D*; Pearce, J (2017) The development of a practical, drift free, Johnson-noise thermometer for industrial applications. Int. J. Thermophysics, 38 (2). p. 25.

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Johnson noise thermometers measure a property that is directly linked to thermodynamic temperature. The measurement of Johnson noise therefore offers the prospect of realising a drift free thermometer. Despite previous attempts to produce a practical Johnson noise thermometer for industrial applications, the technique has so far been limited to use in niche research applications exploring discrepancies between practical temperature scales and thermodynamic temperature, or to determine Boltzmann's constant. This has largely been due to the historical use of switched correlators to measure Johnson noise, which limits the sense resistance and measurement bandwidth that can be employed. This constraint limits the Johnson noise signal to levels near the limits of measurement. A new technique that eliminates switching and thereby allows the use of much higher sense resistances and bandwidths to increase the Johnson noise signal is presented. The signal power achieved is up to three orders of magnitude higher than for systems using a switched correlator. Results so far indicate that measurement performance is compatible with the requirements of industrial applications. Specifically, uncertainties of < 0.3 ºC (95 % confidence) were demonstrated for measurements near ambient temperature within 7 s.

Item Type: Article
Keywords: Johnson noise thermometer, Johnson noise, drift-free, thermometer
Subjects: Engineering Measurements
Engineering Measurements > Thermal
Divisions: Engineering, Materials & Electrical Science
Identification number/DOI: 10.1007/s10765-016-2156-8
Last Modified: 02 Feb 2018 13:12
URI: http://eprintspublications.npl.co.uk/id/eprint/7432

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