Improvement of methods and means of thermal imagers verification and calibration

Abstract

This paper suggests the verification and calibration method of thermal imagers that consists in comparison of temperature readings obtained by contact and thermal imaging method. The experimental setup has been developed to confirm the reliability of the proposed method. The main element of experimental setup is an emitting surface in the form of rectangular plate that measures 330×200×4 mm. The plate is covered with paint which emissivity factor is not less than 0,96. The paper presents the results of temperature field calculations on the plate emitting surface. The temperature field of the plate emitting surface has been determined by the contact method using chromel-alumel thermocouples and thermal imaging method. As a result of the obtained temperature values analysis, it has been concluded that if the plate emitting surface temperatures close to 50 °C, the heat exchange of the plate with the ambient air plays a significant role. The air heaters are applied in order to reduce the heat flows dissipation from the plate emitting surface into the environment. The heaters are two aluminum-magnesium alloy plates attached to the end face of the emitting surface. The metal heat exchangers – coils are installed on the surfaces of the plates and connected by hoses to the liquid thermostat. One of the plates heats the air flowing around the emitting surface, and another one prevents the emission thermal expansion into the environment. As a result of heaters application, the heat exchange intensity of a plate radiating surface with environment decreases. Moreover, recommendations about the choice of heaters sizes have been given. The main advantages of the method proposed are the following: ensuring high isothermic of the emitting surface throughout the height of the plate; accuracy of the temperature maintaining at a given level; reducing the device transition time to steady-state regime.