基于跨波长调制和直接吸收光谱的宽量程多气体检测方法

针对可调谐半导体激光吸收光谱技术(Tunable Diode Laser Absorption Spectroscopy,TDLAS)在煤矿、石油化工领域进行气体浓度检测时，遇到的高精度、宽动态范围需求，采用时分复用的方法，将直接吸收光谱技术(Direct Absorption Spectroscopy,DAS)和波长调制光谱(Wavelength Modulation Spectroscopy,WMS)技术的优势相结合，完成了高精度、宽量程和免标定多气体检测系统的设计。设计激光器的驱动为线性扫描输出和叠加不同高频调制扫描输出的周期信号，用于完成高低浓度反演算法的时分复用计算，通过实验优化选择检测气体的吸光度拐点，实现对气体浓度的高精度、宽量程检测。在室温和常压下，通过实验分别对CH₄、CO和C₂H₂三种气体体积浓度进行检测，确定了两种算法最佳拐点吸光度约为0.026 cm^-1。系统对CH₄、CO和C₂H₂三种气体体积浓度的检测量程分...

Wide-range multi-gas detection method based on wavelength modulation spectroscopy and direct absorption spectroscopy

When tunable diode laser absorption spectroscopy (TDLAS) is applied to the field of coal mine and petrochemical industry for gas concentration detection, it often needs to meet the requirements of high precision and wide dynamic range. Therefore, we use the time-division multiplexing method to combine the advantages of direct absorption spectroscopy (DAS) and wavelength modulation spectroscopy (WMS) technology to complete a high-precision wide-range calibration-free multi-gas detection system. The driving signal of the laser is designed as a periodic signal, which has linear scanning output signal superimposed with different high-frequency sin-wave modulation. It is used to complete the simultaneous calculation of low and high concentration inversion algorithms by time division multiplexing technology. Moreover, by optimizing the absorbance inflection point of the detected gas, the high-precision and wide-range detection of the gas concentration is realized. Under room temperature and pressure, the concentrations of CH₄, CO and C₂H₂ are detected by experiments, and the absorbance at the optimal inflection point of the two algorithms is determined to be about 0.026 cm?1. The detection range of the system for the concentration of CH₄, CO and C₂H₂ are 0-100%, 0-5000×10?6 and 0-1000×10?6, respectively. And also, the minimum concentration detection limits are 2.27×10?4, 0.21×10?6, and 1.68×10?6. The above analysis also shows that the system meets the requirements of wide dynamic range and the accuracy is better than the current coal mine industry standard in the whole range. Moreover, this method can meet the needs of various industrial field applications, and is conducive to promoting the application of laser absorption spectroscopy in industrial processes, security and other fields.