以可调谐激光二极管吸收光谱技术为基础,结合波长调制光谱技术,对不同体积浓度的二氧化碳气体进行检测。分别分析正弦波调制 信号的不同调制电压及调制频率对二次谐波信号波形及峰值的影响。结果显示当调制电压为0.25 V、调制频率为10 kHz时,得到 的二次谐波信号较好。在此基础上,利用实验室中搭建的单光路测量系统对不同浓度的CO2气体进行检测,得到气体浓度与二次谐波 峰值线性相关系数为0.998,系统的检测极限为450 ppm。研究为该类系统调制系数的选择提供了实验依据,为工业应用打下了基础。

Based on tunable diode laser absorption spectroscopy, combined with wavelength modulation spectroscopy technology, different volume concentration CO2 was selected to be measured. The influence of modulation voltage and modulation frequency of sine wave on second harmonic signals was observed. Results show that the signals perform well when modulation voltage is 0.25 V and modulation frequency is 10 kHz. CO2 with different concentration was measured by using the single optical system set up in the laboratory. The results show that the correlation coefficient of the concentration and the peak value of the second harmonic signals is 0.998. Moreover the detection limit is 450 ppm. The experiment result provides definite basis for choosing modulation parameters of such system and can build foundation for industry application.