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Thermodynamic temperature by primary radiometry.

Anhalt, K*; Machin, G (2016) Thermodynamic temperature by primary radiometry. Philos. Trans. R. Soc. Lond. A, Math. Phys. Eng. Sci., 374 (2064). 20150041

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Above the freezing temperature of silver (1234.93 K) the International temperature scale of 1990 (ITS-90) realises a temperature, T90, in terms of a defining fixed-point blackbody and Planck's law of thermal radiation in ratio form. Alternatively by using Planck's law directly thermodynamic temperature can be determined by applying radiation detectors calibrated in absolute terms for their spectral responsivity. With the advent of high-quality semiconductor photo-diodes and the development of high-accuracy cryogenic radiometers during the last two decades radiometric detector standards with very small uncertainties in the range of 0.01~0.02% have been developed for direct, absolute radiation thermometry with uncertainties comparable to the uncertainties of approximating thermodynamic temperature T by T90. This article gives an overview of a number of design variants of different types of radiometer used for primary radiometry, and describes their calibration. Furthermore, details and requirements regarding the experimental procedure for obtaining low uncertainty thermodynamic temperatures with these radiometers are presented, noting that such radiometers can also be used at temperatures well below the silver point. Finally, typical results obtained by these methods are reviewed.

Item Type: Article
Keywords: New kelvin, new SI, primary radiometry
Subjects: Engineering Measurements
Engineering Measurements > Thermal
Identification number/DOI: 10.1098/rsta.2015.0041
Last Modified: 02 Feb 2018 13:13
URI: http://eprintspublications.npl.co.uk/id/eprint/7047

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