A novel method of gas concentration calibration for tunable diode laser absorption spectroscopy, in which spectral analysis and harmonic signal intensity ratio measurement are combined, is proposed in this study. A harmonic signal is extracted from a transmitted light intensity by spectral analysis. The ratio of the second harmonic to the first harmonic is proportional to the gas concentration. The noise caused by electronics and environment is filtered out via frequency-domain filtering, and the harmonic ratio measurement eliminates the effects of light intensity fluctuations. The accuracy and effectiveness of the proposed method are verified by simulation and experiment. Experimental results show that the relative error of measurement is less than 3% and the correlation coefficient between measurement and calibration line is 0.9991.

中文翻译：

---

基于光谱分析和谐波比的痕量气体检测

提出了一种可调谐二极管激光吸收光谱中气体浓度标定的新方法，该方法将光谱分析和谐波信号强度比测量相结合。通过光谱分析从透射的光强度中提取谐波信号。二次谐波与一次谐波的比例与气体浓度成正比。电子器件和环境引起的噪声通过频域滤波被滤除，谐波比测量消除了光强度波动的影响。通过仿真和实验验证了该方法的准确性和有效性。实验结果表明，测量的相对误差小于3％，测量线与校正线的相关系数为0.9991。