Multiwavelength pyrometry: Radiance temperature versus wavelength curve should be used for temperature determination

In multiwavelength pyrometry it is very difficult to represent the wavelength variation of emissivity so that a ‘‘correct’’ blackbody temperature T0 is obtained. On the other hand, use of Tr’s, the radiance temperature, permits the calculation of the blackbody temperature T0. In all cases studied up to now, in the wavelength range 0.4–4 μm, we have a linear relationship between Tr and L, the wavelength, Tr = Tlin − hL, where Tlin is the calculated blackbody temperature.