From The 9th International Temperature Symposium, March 19 – 23, 2012 Anaheim, CA
Proceedings published by the American Institute of Physics, “Temperature: Its Measurement and Control in Science and Industry”
Pyrometry of Materials With Changing, Spectrally-Dependent Emissivity — Solid & Liquid Metals
Abstract. Spectropyrometers have been available for fifteen years and the large volume of data collected has confirmed that emissivity is best described as a property of a sample’s condition rather than a property of a material; any conventional pyrometer that depends on assumed behavior or tabulated values of an emissivity is unlikely to be accurate. The advanced spectropyrometric technique in radiation thermometry discussed here uses hundreds of narrow wavebands over broad spectral bandwidths to accurately measure temperatures despite initially unknown and constantly changing emissivity. Metals and especially liquid metals are an extreme example; these exhibit substantial changes in both the magnitude and the spectral dependence of emissivity with time and processing. The spectropyrometer determines emissivity behavior from the data collected for every measurement, displaying and saving the thermal spectra as well as temperature, tolerance, and emissivity. Extensive testing carried out by third-party users comparing the results of multi- wavelength spectropyrometers with contact techniques on liquid metal targets shows that properly-used thermocouples agree with spectropyrometers to within a few tenths of a percent of the measured values.
Keywords: SpectroPyrometer, pyrometer, pyrometry, radiation thermometry, emissivity, temperature.