A NEW MEASURING METHOD TO DETERMINE MATERIAL SPECTRAL EMISSIVITY

Emissivity is a measure of how well a real surface can radiate energy as compared with a blackbody. This characteristic radiative number is usually determined by means of optical pyrometry. By contrast an indir ect measurement method has been developed which enables the determinat ion of the normal spectral emissivity of various materials at a specif ic wavelength, A heat flow induced in a test body by the absorbed irra diation of a laser beam may be correlated with the spectral emissivity of its surface. The theory of the measuring principle is discussed an d the feasibility of the method evaluated by means of practical experi ments utilizing a thermopile built up using a thick film technique.