Temperature Measurement Using the Wedge Method: Comparison and Application to Emissivity Estimation and Compensation

Temperature measurement based on infrared radiation depends on correctly adjusted emissivity. However, emissivity configuration is complex as emissivity is not normally known with precision; it is influenced by radiation reflections and can also vary with the temperature. The wedge method is a temperature measurement method which assures the selection of the correct emissivity configuration using an infrared camera to take images of a wedge region. Within the wedge, a virtually closed cavity for radiation is created. Although this method outperforms traditional infrared measurement, no comparison has yet been carried out under real industrial conditions which would provide information about emissivity variations. This paper proposes a method to measure temperature using the wedge method in industrial environments and compares the results with the temperature measurement acquired from a calibrated infrared line scanner. Using the wedge method, it is possible to accurately estimate emissivity profiles under real working conditions. A method to apply these profiles for emissivity compensation is also proposed in this paper. Conclusions give the analysis of the strengths and weaknesses of the two methods and provide recommendations and guidelines for technicians interested in temperature measurement and emissivity estimation and compensation.