A Monte Carlo Simulation of Measurement Uncertainty in Radiation Thermometry Due to the Influence of Spectral Parameters

While radiation thermometry is well-developed for laboratory calibrations using high-emissivity sources, the effect of spectral emissivity in real-world conditions, where emissivity ranges from 0 to 1, is usually not considered. Spectral parameters that influence non-contact temperature measurements are often neglected even in laboratory conditions. These parameters become more important with decreasing emissivity and at lower temperatures, leading to increased uncertainty contributions to the measurement result. In this manuscript, we analyze the impact of various influential spectral parameters using the constructed spectral Monte Carlo simulation of radiation thermometry. The investigation covers the influence of spectral and related parameters, namely spectral emissivity, reflection temperature, spectral sensitivity and atmospheric parameters of temperature, relative humidity and distance of the path in the atmosphere. Simulation results are compared to experimental results, overestimating sensitivity to humidity by 23–27% and sensitivity to emissivity and reflected temperature within 10% at given conditions. Multiple cases of radiation thermometer (RT) use are simulated for measurement uncertainty: high temperature RT use as the reference in calibration by comparison, the use of a flat plate calibrator for RT calibration, measurements with a RT using emissivity input data from literature with relatively high uncertainty and temperature measurements with a RT using emissivity data, obtained with FTIR spectroscopy with relatively low uncertainty. Findings suggest that spectral uncertainty contributions are often unjustifiably underestimated and neglected, nearing extended uncertainty contribution of 1.94 °C in calibration practices using flat plate calibrators with emissivity within 0.93 and 0.97 and 1.72 °C when radiation thermometers with spectral ranges, susceptible to atmospheric humidity, are used on black bodies.