Dynamic Response Characteristics Analysis Of Thermocouple

With advantages such as favorable performance stability,small volume and wide temperature range,temperature sensors are usually applied to industrial circles in temperature measurement.As common temperature sensors,thermocouples have wide ranges of applications,which are worthy of being researched;therefore,thermocouples are selected in this article for performance analyse.The dynamic response characteristic of thermocouples is a significant constituent part of the performance of thermocouples,representing for the ability of thermocouples on tracking temperature changes;therefore,it is important to analyze the dynamic response characteristic of thermocouples.There are many factors affecting the dynamic response characteristic of thermocouples,and it is very difficult to analyze the dynamic response characteristic accurately with only theoretical generalization or experimental measurement.Therefore,analyze the dynamic response characteristics of thermocouples through the combination of theoretical analyse and experimental analyse demonstrates important research values.A thermocouple dynamic response characteristic test system is designed in this article,including thermocouples,opposed photoelectric sensors,heating equipment(thermostatic baths and industrial heat guns),thermal baffles,the data acquisition card and the computer.A bare thermocouple and a sheathed thermocouple are adopted to acquire,during the test process,the data acquisition card is adopted to collect the temperature of thermocouples and the data of corresponding moment,and the voltage of opposed photoelectric sensors and the data of corresponding moment,which are recorded through real-time temperature tracking program.To further analyse the dynamic response characteristics of the two thermocouples,the structure of transfer functions of the two thermocouples were first obtained through theoretical analyse,then the positive and negative phase step temperature stimulation are conducted to the two thermocouples,and based on the obtained experimental data and the structure of transfer functions of the two thermocouples,the parameters of transfer functions of the two thermocouples were identified.In order to achieve model parameters near to the actual conditions,reasonable guess is conducted to improve the transfer function structure of thethermocouples acquired from theoretical modeling and the parameters are identified again through experimental modeling.According to identification results,the transfer function structure of the first order inertial delay and the ARMA disturbance term is closer to the actual transfer function structure of the two thermocouples.