Chapter 1 Overview of Radiation Thermometry

Abstract

Publisher Summary This chapter presents an overview, classification, and common terminology of radiation thermometry. This chapter presents a general introduction to radiation thermometry from the basic operating principles according to the fundamental laws of thermal radiation to the central problems with the practical application of the technique associated with the unknown emissivity of the surfaces and the effect of the environment. The selection of wavelengths for a measurement is shown to be dependent on the temperature ranges. Some emissivity correction methods are summarized and typical radiation thermometers and their operating mechanisms are outlined, including traditional single detector, thermographic imagers, and various optical fiber thermometers. Radiation thermometry belongs to the noninvasive class of temperature measurement techniques. It has several unique advantages such as the ability to reliably follow rapid temperature changes. In some cases, it can measure small objects or map the temperature distribution with a spatial resolution of a few micrometers. More recently, radiation thermometers have also been used in semiconductor processing, asphalt and cement industry, paper industry, food industry, and advanced manufacturing such as laser welding and laser cutting. When a radiation thermometer is used to measure the temperature of a real surface, two issues arise. The first is the unknown emissivity of the surface (which affects the emitted radiation from the target), and the second is the influence of the emission from and absorption by the environment (which can significantly influence the radiation reaching the detector). The measurement equation of a bandpass spectral radiation thermometer is presented.