激光吸收光谱技术噪声响应特性数值模拟研究

Numerical Simulation Research on Noise Response Characteristics of Laser Absorption Spectroscopy Technology

在波长调制激光吸收光谱(WMS)技术的测量过程中,测量系统不可避免地会受到电路硬件噪声、机械振动噪声、环境噪声等干扰因素的影响。以CH在6046.95 cm^(-1)附近的吸收谱线为例,通过数值仿真方法定量研究了WMS技术的噪声响应特性。对不同信噪比下采用FFT滤波方法提取的归一化二次谐波信号的峰值变化进行了比较分析,在此基础上就二次谐波峰值变化的标准差和相对误差与信号信噪比之间的关系进行建模,得到了二者与信噪比之间的近似表达式,拟合R^(2)值分别为0.99957、0.99352。研究结果表明,通过数据平均的方式无法从根本上消除噪声对WMS测量准确度的影响,所建立的数学模型为噪声影响下的WMS测量结果的修正提供了思路。

In the measurement process of wavelength modulated laser absorption spectroscopy(WMS),the measurement system will inevitably be affected by circuit hardware noise,mechanical vibration noise,environmental noise and other factors.Taking the absorption spectrum of CHnear 6046.95 cma^(-1)s an example,the noise response characteristics of WMS technology are quantitatively studied by numerical simulation methods.The peak value changes of normalized second harmonic signals extracted by FFT filtering method under different signal-to-noise ratio are compared and analyzed.On this basis,the relationship between standard deviation and relative error of the second harmonic peak value change and the signal-to-noise ratio was modeled.Moreover,the approximate expression between the two and the signal-to-noise ratio was obtained,and the fitting R^(2) value are 0.99957 and 0.99352,respectively.Research results show that the method of data averaging cannot fundamentally eliminate the influence of noise on the accuracy of WMS measurement.The mathematical model established in this paper provides an idea for the correction of WMS measurement results under the influence of noise.