Understanding the radiation thermometers

Abstract

Radiation thermometers use the laws of thermal radiation to compute the temperature as a function of the measured spectral radiance. The more precise calculations involve the integration of Planck's Law, which turns the mathematical developments more complex. In this article, whenever possible we use the concept of monochromatic radiation thermometers, which has the advantage of facilitating mathematical developments and allowing the reader to obtain more easily an overview of the instrument behaviour. In addition, we deal with three important types of thermometers: total radiation, spectral band, and ratio thermometers. Some concepts such as radiance and exitance were also presented.