The integral six‐color pyrometer: Linear dependence of the radiance temperature Tr on the wavelength lambda

The emissivity E of a radiating body as a function of wavelength can be expressed as (ln E)/C2=a+bL+cL2+dL3+eL4+ ... . In our first papers we assumed that the variation is linear; only two coefficients are needed. Later we developed ‘‘A New, General Method of Temperature Determination,’’ which consists of evaluating Te, the calculated blackbody temperature, using one, two, three, and four coefficients (with six wavelengths) in the equation for (ln E)/C2, as well as evaluating its error d’Te. The error is due to the uncertainty in the coefficients. The ‘‘correct’’ Te, called T*e, is obtained by averaging the Te’s, using the d’Te’s as weighting factors. We now have found that the radiance temperature Tr is a linear function of the wavelength over a large wavelength range: from 0.40 to 5.00 μm at low temperature and from 0.40 to 1.00 μm at high temperatures. In practical applications, one should use a wavelength range extending from 0.40 μm through the range where the radiation intensity is at its maximum. I...