热电偶时间常数测试中阶跃温升信号的研究

Study on step temperature rise signal in thermocouple time constant test

为了对热电偶时间常数进行准确测试,采用上升时间5μs、功率500W的大功率半导体激光器作为系统激励源对热电偶进行加热的方法,对时间常数进行了理论分析和实验验证。利用半导体激光器输出连续且光斑能量均匀稳定的优点,解决了原测试系统中传统激励源作用机理的限制。结果表明,由于半导体激光器输出功率恒定,利用闭环反馈控制激光功率的方法,产生激光阶跃温升信号,保证了热电偶的均匀加热,得到了期望的平衡温度;4支不同热电偶时间常数分别测得为2.806s,3.094s,2.229s和2.457s。该反馈控制器具有较强的鲁棒性,测试系统可激发较理想的阶跃温升信号,为热电偶时间常数测试提供高质量的激励源。

In order to accurately test the thermocouple time constant,a high power semiconductor laser with rise time of 5μs and power of 500W was used as excitation source to heat the thermocouple.Theoretical analysis and experimental verification were carries out about time constant.Because of continuous output of semiconductor laser and stable uniformity of spot energy,the restriction of traditional excitation source mechanism of the formal test system was solved.The results show that,as the output power of semiconductor laser is constant,by closed-loop feedback control of laser power,laser step temperature rise signal is generated to ensure the uniform heating of thermocouple and obtain expected equilibrium temperature.Time constants of four different thermocouples were 2.806s,3.094s,2.229s and 2.457s.The feedback controller has strong robustness.The test system can stimulate the ideal step temperature rise signal to provide high quality excitation source for thermocouple time constant test.