Noncontact temperature measurement. I. Interpolation based techniques

Abstract

Various ratio pyrometry techniques (two, three, and four color) are analyzed and shown to possess hitherto unknown sources of error under certain conditions. These conditions are shown to arise quite frequently. The ratio method is shown to be better suited to the shorter wavelengths. It has been shown, for various emissivities, that the predicted temperature has an asymptote at some wavelength. Ratio pyrometry methods are shown to be very sensitive to measurement noise and this sensitivity grows quickly with the number of terms in the ratio. The effect of a reference temperature in the system is examined and it is shown that under certain conditions this reference temperature can be used to make accurate predictions regarding the temperature elsewhere in the system even if the emissivity changes.