基于半导体激光器的热电偶时间常数测试系统及不确定度分析

Thermocouple Time Constant Test System and Uncertainty Analysis Based on Semiconductor Lasers

针对热电偶时间常数的测试,采用上升时间为0.6μs、功率为500 W的半导体激光器取代CO2激光器作为激励源,通过对激光光束的整形优化,在20V工作电压和20A工作电流条件下,利用半导体激光器在热电偶测温端形成1050℃阶跃温度。对测量结果进行小波降噪处理,建立测量模型。分析测量结果的不确定度来源,评定测量结果不确定度。实验测得时间常数为1.3268s,扩展不确定度为1.12ms。通过提高激光器输出功率,可在热电偶测温端产生更高的阶跃温度,以实现大量程热电偶时间常数的测试。

In view of the thermocouple time constant test, the semiconductor laser with 0.6us rise time and 500 W power is selected as the excitation source instead of the CO2 laser. By shaping the laser beam, 1050℃ step temperature at the measuring side of the thermocouple is achieved as the laser operates at 20 V working voltage and 20 A working current. The measurement results are processed by wavelet denoising, and the measurement model is established. The uncertainty of the measurement results is evaluated by analyzing its sources. The measured time constant is 1. 3268 s, and the expanded uncertainty is 1.12 ms. The time constant of large-range thermocouples can be tested through increasing the laser power and producing a higher step temperature at the measuring side of the thermocouple.