Optimization of Thermal Radiation Source For High Temperature Infrared Thermometer Calibration

Abstract

Industrial level infrared thermometers are being increasingly designed to measure temperatures above 500 °C. A thermal radiation source is needed to calibrate these instruments. The infrared thermometers designed to measure these temperatures generally measure with a smaller field-of- view. This means there is a possibility of using a blackbody cavity as the thermal radiation source. A previous attempt was made to use a cavity mounted inside of a furnace meant for thermocouple calibration for a thermal radiation source. However, when the cavity’s emissivity was measured, it was found the emissivity was not constant for different wavelengths and was very dependent on cavity position. This paper discuses a new attempt to mount a cavity inside a thermocouple furnace with much better temperature uniformity. It discusses the measurements made to verify the emissivity of the cavity using industrial radiation thermometers. It also talks about measurements made with industrial handheld infrared thermometers and compares these measurements to measurements made using other thermal radiation sources and the associated measurement uncertainty.