鉴于2次谐波外的其他谐波成分中依然蕴含着浓度信息,提出了基于2次+4次谐波、2次+4次+6次谐波、2次+4次+6次+8次谐波的三种浓度反演方法,推导出各自的气体浓度反演表达式,评估了所提反演方式对应的最佳调制度,分析了气体浓度检测系统中噪声干扰的主要存在形式,在理论上证明了所提出的联合多次谐波分析方法可以显著提升噪声抑制能力,并给出了用于参考的实验方案。仿真结果表明:与基于2次谐波峰值的浓度反演方法相比,2次+4次谐波可以使浓度反演误差降低31.38%,2次+4次+6次谐波可以使浓度反演误差降低42.03%,2次+4次+6次+8次谐波可以使浓度反演误差降低47.45%。

In view of the fact that other harmonic components besides the second harmonic still contain concentration information,three concentration inversion methods based on 2nd-/4th-harmonics, 2nd-/4th-/6th-harmonics, and 2nd-/4th-/6th-/8th-harmonics, as well as their corresponding expressions, are presented while the optimal value of the modulation depth for each inversion method is evaluated. The main forms of noise interference in gas concentration detection systems are also analyzed and the usefulness of multiple harmonic analysis for noise suppression is proved theoretically. Finally, an experimental verification scheme is given for reference. Our simulation's results indicate that the above methods can reduce concentration inversion errors by 31.38%, 42.03%, and 47.45%, respectively, as compared with the 2nd-harmonic-based method.