Analysis of calibration methods for direct emissivity measurements

We analyze two important points related to the experimental emissivity measurements in this paper: the radiometer calibration accuracy and its stability to determine the required frequency of calibration. The usual two-temperature calibration method is compared to a more accurate method, which uses the measurement of blackbody radiation at several temperatures. Additionally, the suitability of the two-temperature method is studied as a function of the gap between both temperatures. Differences higher than 200 degrees C are needed to obtain an acceptable calibration. The temporal stability of the calibration and the influence of the environmental conditions are also analyzed. (C) 2010 Optical Society of America