可调谐二极管激光吸收光谱(TDLAS)技术与长光程吸收池相结合构成的痕量气体检测系统具有高灵敏度、高精度、反应快等优点。由于激光器噪声、电子学噪声以及光学噪声的存在,实际测量得到的二次谐波信号出现偏差。分析了TDLAS谐波信号的特征,建立了谐波信号的数学模型,利用较高浓度气体的二次谐波信号作为标准曲线,对待测气体的谐波信号进行线性回归,并研究了相关系数和气体浓度的规律。以CO,CO2气体为例,验证了算法。

Trace gas analyzers based on the tunable diode-laser absorption spectroscopy (TDLAS), combined with the long-path absorption cell, provide high sensitivity, high precision and fast response measurements of trace gases. The interferences caused by laser noise, electronic noise and optical niose, result in measurement error of the second harmonic signals. Characteristics of the second harmonic signal with TDLAS are analyzed. Mathematical model of the second harmonic signal is set up. Linear regression method is used to deal with the second harmonic signal of the measured trace gas using the signal of high concentration gas as the standard. The relationship between concentrations and corresponding correlation coefficients is also studied. Some measurements of CO and CO2 are presented, and the validity of the arithmetic is proved.