Radiation thermometer


Employing absolute measurements of blackbody radiation, primary thermometry can also be based on Planck's law for the spectral radiance (versus frequency ν) Lν (spectral-band radiation thermometry) or the Stefan-Boltzmann law for the total (frequency-integrated) radiance L (total radiation thermometry) of a blackbody at temperature T:


Here, σ = 2 π5κ4 /(15 c02 h3) is the Stefan-Boltzmann constant.

"Absolute" radiometric determination of high thermodynamic temperatures is now possible with an uncertainty similar to or even smaller than that of the ITS-90 fixed points (about 40 mK at the silver freezing point close to 1235 K, which result from the necessity of relating thermodynamic temperatures to the TPW temperature).


  1. M Planck, Zur Theorie des Gesetzes der Energieverteilung im Normalspektrum, Verhandlungen der Deutschen Physikalischen Gesellschaft 2, 1900, pp 237-245
  2. D Hoffmann, Schwarze Körper im Labor, Physikalische Blätter 56, 2000, pp 43-47
  3. J E Martin, N P Fox, P J Key, Metrologia 21, 1985, pp 147-155
  4. T J Quinn, J E Martin, A radiometric determination of the Stefan-Boltzmann constant and thermodynamic temperatures between -40 °C and +100 °C, Philosophical Transactions of the Royal Society of London A 316, 1985, pp 85-189
  5. N P Fox, Metrologia 32, 1995/1996, pp 535-543
  6. D W Allen, R D Saunders, B C Johnson, C E Gibson, H W Yoon, The Development and Characterization of an Absolute Pyrometer Calibrated for Radiance Responsivity, TMCSI, Vol 7, Chicago, edited by D C Ripple, 2003, pp. 577-582
  7. D R Taubert, J Hartmann, J Hollandt, J Fischer, Investigation of the Accuracy of the ITS-90 with Reference to Thermodynamic Temperature in the Range from 400 °C up to 600 °C, TMCSI, Vol 7, Chicago, edited by D C Ripple, 2003, pp. 7-12
  8. J Hollandt, R Friedrich, B Gutschwager, D R Taubert, J Hartmann, High-Accuracy Radiation Thermometry at the National Metrology Institute of Germany, the PTB, submitted to High Temperatures - High Pressures
  9. J E Martin, P R Haycocks, Metrologia 35, 1998, pp 229-233