Spectral radiancy pyrometer

A disappearing filament (Figure 8.7) pyrometer is a form of a spectral radiancy pyrometer, which is a device that evaluates... 

For maximum sensitivity, the wavelength of the infrared pyrometer should also be selected based on where the spectral radiancy changes most rapidly. For example, in the temperature range depicted in Figure 8.3, a frequency of 1.5 x 10u Hz (2 /im) will permit more precise temperature measurement than a frequency of 0.4 x 1014 Hz (7.5 /im). 

In ratio pyrometers [5], a device is designed to measure the spectral radiance temperatures and 7, at two wavelengths and X. Then, the true temperature Tm is determined from the ratio temperature Tra and is given by... 

To overcome the problems faced by the single-wavelength radiation thermometer and the ratio pyrometer, a double-wavelength radiation thermometer (DWRT) measures the spectral radiance itself at two distinct wavelengths for surface temperature evaluation. For this method to be used, the emissivity compensation function e i = fl v) must be defined. A detailed description of the principle for DWRT can be found in Ref. 53. When the emissivity relation x.i = Ae ) at two distinct wavelengths e i = fl v) is established, the true temperature on the measured surface can be determined from the inferred temperature, which is defined as... 

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