Impedance bridge for surface temperature measurement

THE NONCONTACTING emissivity-free measurement of surface temperatures is a major problem in many industrial processes. In order to reproduce the temperature conditions that are found to give a satisfactory product, it is often desired to measure the surface temperature of metallic objects such as rolls or molds. The reliability of radiation pyrometers for these applications is frequently questionable for the following reasons: 1. The emissivity of highly polished surfaces is often uncertain and varying. 2. An error results from the absorption of radiation by gases or liquids interposed between the measuring element and the surface whose temperature is to be measured.