Temperature Measurement of Transparent Solid Bodies Pyrometric, Contactless Method All solid bodies which partially or totally transmit thermal radiation in the wavelength of visible and infrared radiation, are classified as transparent bodies . The notation used to consider pyrometric methods for measuring the surface temperature of solid bodies has already been introduced in Section . It will be recalled that solid bodies, which have a transmission factor limited to a = 0, are non-transparent bodies in the whole range of wavelengths used in optical pyrometry . The same notation will be used in this chapter | Temperature Measurement Second Edition L. Michalski K. Eckersdorf J. Kucharski J. McGhee Copyright 2001 John Wiley Sons Ltd ISBNs 0-471-86779-9 Hardback 0-470-84613-5 Electronic 18 Temperature Measurement of Transparent Solid Bodies Pyrometric Contactless Method All solid bodies which partially or totally transmit thermal radiation in the wavelength of visible and infrared radiation are classified as transparent bodies. The notation used to consider pyrometric methods for measuring the surface temperature of solid bodies has already been introduced in Section . It will be recalled that solid bodies which have a transmission factor limited to i 0 are non-transparent bodies in the whole range of wavelengths used in optical pyrometry. The same notation will be used in this chapter. The general conditions to be considered in this chapter are illustrated in Figure . Behind and in the background of the transparent body 1 whose temperature is to be measured is another body 2 with a temperature Simultaneously the investigated surface may be irradiated by another body 3 with a temperature if. Thus the radiation incident upon the pyrometer consists of the radiation from the investigated surface the background radiation transmitted through the investigated body and the radiation from body 3 reflected from the investigated surface. Consequently the pyrometer indication will be incorrect since errors are introduced by the radiation from both the background and the nearby influencing body. Errors caused by reflected radiation can be eliminated by either applying a shield to shadow the influencing body 3 in Figure or by applying a pyrometer with zerosensitivity in the wavelength range emitted by this body 3 and reflected by 1. The error caused by background radiation can be minimised if not completely eliminated by proper choice of a pyrometer whose operating wavelength is within the range where the spectral transmissivity of the body 1 is as low as possible. To
