基于脉冲激光负阶跃响应的高速热电偶 时间常数测量方法

热电偶的时间常数是表征其动态特性的关键参数，利用激光激励获得温度阶跃是测量高速热电偶时间常数的主要手段。本文对比分析了正、负阶跃激光激励时的热电偶传热过程，指出负阶跃过程更符合时间常数测量的基本理论。通过建立阶跃调制激光和脉冲调制激光的负阶跃过程中热电偶的响应模型并计算，表明脉冲激光激励可有效解决阶跃调制激光测试结果偏慢的问题。通过搭建实验系统，相同条件下测得时间常数分别为73.78和41.34 ms,脉冲激光测试更能体现热电偶的极限测温速度。实验结果还表明不同脉冲能量对时间常数测量结果基本没影响，更小尺寸热电偶响应速度更快，强制对流环境对热电偶时间常数测量结果影响巨大。

Time constant measurement method of high-speed thermocouple based on negative step response of pulsed laser

The time constant of the thermocouple is a key parameter of its dynamic characteristics. Obtaining temperature step by laser excitation is the main way to measure the time constant of the high-speed thermocouple. The heat transfer process of thermocouple excited by positive and negative step laser is compared and analyzed in this article. It is pointed out that the negative step is more consistent with the theory of time constant. The response model of thermocouple in the negative step of step modulated laser and pulse modulated laser is formulated. It shows that the pulsed laser can effectively solve the problems existing in experimental results of the step laser. The time constants measured under the same conditions are 73. 78 and 41. 34 ms, respectively. The limit performance of thermocouple response can be obtained by pulse laser test. Experimental results also show that the pulse energy has little effect on the measurement results of the time constant. Smaller thermocouples respond faster. The forced convection has a great influence on the measurement results of the thermocouple time constant.