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Proceedings Paper

Total Radiation Thermometry
Author(s): J. E. Martin; T. J. Quinn
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Paper Abstract

A total radiation thermometer (comprising a cryogenic radiometer which measures the total radiation emitted from a black-body cavity) has been developed at NPL as an alternative instrument to the traditional gas thermometer for measuring thermodynamic temperature.' The total radiant exitances, E(T) and E(To), of a black body at temperatures T and T. respectively, can be expressed as a ratio E(T)/E(To) = T4/To4, where To = 273.16 K, the temperature of the triple point of water. Hence, by measuring the ratio E(T)/E(To) a value of T can be determined. The uncertainty in T using this thermometer is about 1 mK, equivalent to measuring the black-body radiation with an uncertainty of about 1.5 parts in 105. If at the same time the black-body temperature is measured by a platinum resistance thermometer calibrated on IPTS68, a value of T68 can be realised, and differences T-T68 can be deduced. In this paper values of T-T68 will be presented in the temperature range -130 to +110°C and compared to recent gas thermometry in the same range. This will be followed by a discussion of the changes that are being made to the apparatus so that the temperature range can be extended up to 460°C. In particular, (a) modifying the radiometer so that it is possible to measure the increased ratio E(T)/E(T0), and (b) the development of a new black body of unusual design.

Paper Details

Date Published: 26 September 1989
PDF: 7 pages
Proc. SPIE 1109, Optical Radiation Measurements II, (26 September 1989); doi: 10.1117/12.960724
Show Author Affiliations
J. E. Martin, National Physical Laboratory (United Kingdom)
T. J. Quinn, Bureau International des Poids et Mesures (France)

Published in SPIE Proceedings Vol. 1109:
Optical Radiation Measurements II
James M. Palmer, Editor(s)

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