Since the publication of the Theory and Practice of Radiation Thermometry in 1988, the designs of radiation thermometers have undergone drastic changes. With the exception of few industries, the disappearing filament pyrometers are not commonly used. The improvements in detector performance had led to an expansion of detector-based radiation thermometry where the temporally-stable response of the detector is needed to maintain the calibration. Also, the improvements in micro-bolometer array performance along with lower costs have led to inexpensive hand-held thermal imaging cameras for non-destructive testing and thermal diagnostic uses. Although thermal imagers can be calibrated for use as transfer standards, radiation thermometer designs with the lowest measurement uncertainties are obtained using spot-radiation thermometer designs which are capable of viewing the fixed-point blackbodies directly. In this chapter, the instrument design and characterizations of spot-radiation thermometers capable of transferring the temperature scales with the lowest uncertainties will be discussed. The radiation thermometers can be calibrated using the International Temperature Scale of 1990 (ITS-90) or the radiation thermometers can be calibrated using absolute radiometry for thermodynamic temperature determinations. The chapter is also limited to radiation thermometers which operate in the visible to the near-infrared wavelength regions. The choice of the detector and optimization of the detector for stability and linearity will be discussed. The characterizations of radiation thermometers for size-of-source effect (SSE) will be discussed.
Radiometric Temperature Measurements and Applications