TEMPERATURE COEFFICIENTS OF TOPCON RADIATION THERMOMETERS
− The ambient or instrument temperature affects the outputs of a standard radiation thermometer through various parts such as a detector, a feedback resistance and an interference filter. Usually the output was corrected by one coefficient assuming the linear dependence. If the filter wavelength changes, the dependence is different at each target temperature. We measured the temperature coefficients of Topcon radiation thermometers at different target temperatures and found the target temperature dependence as well as the feed back resistance dependence. Therefore a high stability radiation thermometer requires controlling the detector, filter and amplifier temperatures.
Calibration and Characterization of the Transfer Standard Radiation Thermometer for an APMP Intercomparison
An Asia‐Pacific Metrology Program (APMP) key comparison of radiance temperature in 0.65 μm was carried out from 1997 to 2000 among seven institutes: NMIJ, KRISS, NIM, CSIRO, NMC, KIM‐LIPI and ITRI. Afterward an APMP supplementary comparison of radiance temperature in 0.9 μm was started. Both of the comparisons employ a transfer standard radiation thermometer as a transfer instrument. This paper describes the calibration and characterization of the 0.65 μm transfer‐standard radiation thermometers. The 0.65 μm thermometer was calibrated according to the ITS‐90. A copper‐point calibration, spectral responsivity measurement and nonlinearity measurement were carried out. The measured spectral responsivity was multiplied by the Planck equation and was integrated over wavelength. The coefficient was determined by the copper‐point calibration. The integral scale of the output V at temperature T was approximated by an interpolation equation, V(T)=C/[exp{c2/(AT+B)}−1]. Here c2 is the second radiation constant and t...
Nonlinearity characteristics of radiation thermometers
Accurate calibration of radiation temperature requires knowledge of radiation thermometer nonlinearity. The nonlinearity at doubled incident radiation was measured at various radiance levels by using the dual aperture method. The scale deviation and uncertainty due to silicon detector nonlinearity were calculated. The expanded uncertainty due to the nonlinearity of a 0.65 /spl mu/m radiation thermometer scale was estimated as 0.04/spl deg/C at 2000/spl deg/C. The scale deviation of a 0.9 /spl mu/m radiation thermometer was 0.42/spl deg/C at 2000/spl deg/C.