Research On Feedback Control Method Of Thermocouple Time Constant Test System

With the continuous development of temperature measurement technology and temperature sensor research,the temperature range and dynamic performance of the temperature sensor are getting better and better.Thermocouples are one of the most widely used temperature sensors.Thermocouples are entensively used in aerospace engines,nuclear power plants,military weapons research and chemical metallurgy.The thermocouple time constant is one of the significant dynamic characteristics of thermocouples,which can directly characterize the performance of thermocouples.Aiming at the shortcomings of the existing thermocouple time constant test method,a power modulatable semiconductor laser is proposed as a transient heating source,the output modulated laser is irradiated to the thermocouple temperature measuring node to raise the temperature.By using the high-speed infrared radiation temperature measurement module whose response speed is much better than thermocouple,collecting he temperature at the thermocouple temperature measurement node as its real temperature,and feedback controls laser power of the laser,so that the thermocouple surface can realize reliable step temperature signal excitation,and dynamic response curves and performance indicators of the thermocouple are obtained.In this paper,the mathematical system model is obtained by systematically identifying the thermocouple time constant test system as a whole.By using fuzzy PID control algorithm and single PID control algorithm,the above algorithm is simulated and compared,and the laser is feedback controlled to realize the generation of step temperature source.Since the thermocouple is a first-order model,the response curve is obtained after the step temperature is excited by the thermocouple,and the dynamic response characteristics such as the time constant of the thermocouple are obtained from the curve data.By testing a K-type armored thermocouple,it is found that fuzzy PID control algorithm can generate the step temperature faster and better,which makes the thermocouple test result more reliable.By evaluating the uncertainty of the test results,the source of the components that constitute the uncertainty of the thermocouple time constant is analyzed,and the influence of each component on the test results is calculated.