铠装热电偶动态响应校准过程数值研究

时间常数是描述温度传感器动态响应特性的重要参数。由于实验室校准条件通常难以覆盖温度传感器的实际使用条件，因此基于有限体积法数值仿真研究了插入法和回路电流阶跃响应(loop current step response, LCSR)法校准铠装热电偶动态响应的过程。建立了热电偶保护管、绝缘层、感温层的三维模型，分析了绝缘层MgO不同填充密实度下热电偶的动态响应。结果发现，采用3个极点的方程对LCSR响应数据进行拟合、变换求得的时间常数与插入法获得的时间常数偏差小于10%,为快响应铠装热电偶动态特性的设计、校准提供了一种新方法。

Numerical Simulation for the Dynamic Response Calibration of the Sheathed Thermocouple

Time constant is one of the important parameters for temperature sensor`s dynamic response. Because the calibration conditions usually can`t cover the temperature sensors service conditions, the dynamic responses of a sheathed thermocouple under plunge test and loop current step response (LCSR) test were numerically simulated by the finite volume method. Three-dimensional structure models of the thermocouple with protective tube, insulating layer and sensing layer were established. The dynamic responses of the thermocouple with different MgO ratio in the insulating layer were analyzed. The results show that the time constants obtained by fitted and transformed LCSR data with the equation of three poles agree well with the time constants obtained by the plunge test, and the deviations are less than 10%. These provide a new method for the design and calibration of the fast response sheathed thermocouples.