Research On High-precision Infrared Temperature Measurement Technology Under Low Temperature

Temperature measurement is of great significance in industrial practice.With the rapid development of infrared temperature measurement theory and related instruments,remarkable achievements have been made in the field of medium and high temperature,but there is still big research space for low temperature measurement,especially for high-speed and low temperature measurement.Improving the temperature measurement accuracy is an important research direction.In this paper,based on the high-speed infrared temperature measurement system of track plate in alpine region,two main factors affecting the temperature measurement accuracy are analyzed theoretically and experimentally: the drift caused by the temperature drift of infrared detector and the ambient temperature interference.According to their respective rules,the compensation scheme is designed to improve the temperature measurement accuracy.The main work of this paper is as follows:(1)The infrared temperature measurement model is deduced in detail,and the influencing factors of the temperature measurement accuracy are analyzed.Combined with the working background of the track plate infrared temperature measurement system,the experimental analysis is carried out.The change of the detector working temperature leads to the change of its spectral responsivity curve,which will bring error when applied to the temperature calculation;The radiation received by the detector includes the ambient radiation reflected by the measured target,and the measurement error component is introduced.Based on the above analysis,the main error sources are temperature drift and ambient temperature interference.(2)Based on the heat transfer theory,combined with the heat load calculation of the infrared detector temperature control in the temperature range of-20℃～40℃,a high-precision temperature control scheme based on PID control and thermoelectric refrigeration is designed to ensure the constant working temperature of the detector.By comparing the temperature measurement accuracy before and after the temperature control with the experimental data,it is verified that the temperature control system effectively reduces the measurement error caused by the temperature drift of the detector.(3)A constant temperature calibration system with controllable ambient temperature based on high and low temperature test chamber is built,and the calibration experiments of different ambient temperatures are completed.By analyzing the experimental data,the influence of ambient temperature change on the result voltage response is obtained,and the compensation curve is generated by fitting.Finally,the temperature measurement accuracy before and after compensation is compared through experiments,and the effectiveness of the compensation scheme is verified.