ABSTRACT
The problem of spectral emittance discussed for the disappearing filament pyrometer is present for infrared pyrometers as well. The great advantage of infrared pyrometers is the ability to custom select the wavelength in which to make the temperature measurement. In some regions of the spectrum, materials are highly absorbing of radiant energy while at others the emittance is rather low. Figure 8.11 shows the spectral transmittance of soda-lime-silica glass. Using an infrared pyrometer sensitive the 8-J.Lm range will permit temperature evaluation of the material as if it were a blackbody. 6 However,
if a hot object is to be viewed through the glass (acting as a window), a detector sensitive to wavelengths shorter than 2.7 JJm is necessary.
