Total Radiation Thermometry

J. E. Martin; T. J. Quinn

doi:10.1117/12.960724

26 September 1989 Total Radiation Thermometry

J. E. Martin, T. J. Quinn

Proceedings Volume 1109, Optical Radiation Measurements II; (1989) https://doi.org/10.1117/12.960724
Event: SPIE 1989 Technical Symposium on Aerospace Sensing, 1989, Orlando, FL, United States

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(T_o), of a black body at temperatures T and T. respectively, can be expressed as a ratio E(T)/E(T_o) = T⁴/T_o⁴, where T_o = 273.16 K, the temperature of the triple point of water. Hence, by measuring the ratio E(T)/E(T_o) 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.

Citation Download Citation

J. E. Martin and T. J. Quinn "Total Radiation Thermometry", Proc. SPIE 1109, Optical Radiation Measurements II, (26 September 1989); https://doi.org/10.1117/12.960724

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