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.