Development Of A Low-Temperature Precision Blackbody Source

With the development of sensor technology and microelectronics, theinfrared radiation thermometers have been widely used in the various fields ofindustry and science. Traditionally, they are used in high temperature. Now theyare applied in low temperature case, even, in temperature below-80°C. Blackbodyradiation source is the calibration device of infrared radiation thermometers. Itsimulates meet the Planck’s law. And its performance directly affects the measureaccuracy of infrared radiation thermometers. Therefore, the study of blackbodyradiation is very important, especially in low-temperature blackbody radiation.After the full understanding of the development of the blackbody radiation andits research status, we have a detailed and careful analysis of the theory ofblackbody system. According to the theoretical analysis of the blackbody systemand project design requirements, we developed a low-temperature blackbodyradiation source with a heat exchanger. The blackbody covers the temperaturerange from-80°C to100°C. And we test its performance.The shape of the blackbody cavity is cone-cylinder. The cavity is made ofstainless steel. The cone angle of the cavity is120°. The length of cavity is300mmand diameter is50mm. The inner wall of the cavity is coated with a special paint.The calculated emissivity of the cavity is0.998. The measured emissivity of thecavity is0.997. The measured emissivity agrees well with the calculated one. Theblackbody adopts a stirred fluid bath to achieve temperature uniformity along thecavity. A two class compressor cooling unit starts working for operated attemperatures below an ambient temperature and it can make temperature down to-80°C. Synchronous heating technology is used to make the temperature of the bathstable. Electric heaters are applied in the appliance. The temperature control adoptsthe fuzzy adaptive PID control mode. The experiment results show that thetemperature stability is better than0.05°C/30min. The frost prevention unit willstart working when the blackbody is operated below0°C. It can prevent frost buildup on the wall and the window of the cavity in30mins when operated attemperatures below the dew point temperature of an ambient air.Finally, we assess the temperature measurement uncertainty and emissivitymeasurement uncertainty of the blackbody.