A simple experimental technique for estimation of the band-pass of infrared radiation thermometers

The infrared radiation thermometer is now becoming a very widely used instrument for industrial temperature measurement and hazardous temperature assessment. Its simple design allows a very low manufacturing cost, and hence its widespread adoption as a convenient non-contact thermometer. The spectral sensitivity of these instruments is usually set by the transmission properties of the windows on the pyrometer, and, although the manufacturer usually makes some statement as to the operating wavelength region, it is difficult to know exactly what is being reported. Calibration laboratories often require knowledge of the band-pass for appropriate calculations of uncertainty, corrections for blackbody emissivity, or, as is commonly becoming required, correction of blackbody radiance temperatures for the calibration of cheaper 'fixed emissivity (eg. 95%)' pyrometers. An explicit measurement of the spectral response of the pyrometer would require a tunable IR source, and special attention to the effects of ambient radiation. This paper presents a very simple experimental technique for the estimation of effective pass-band of an IR radiation thermometer using only a mesh and a blackbody radiator at several temperatures. An analysis of the uncertainty in this determination of the band-pass is also presented.