基于积分球气室的光声光谱法气体检测研究

Research on Gas Detection by Photoacoustic Spectroscopy Based on Integrating Sphere Gas Cell

光声光谱技术因其灵敏度高、可靠性强、响应速度快等优点,在气体检测方面得到了广泛的应用。积分球气室内壁的高反射率涂层能有效增大光程,所以常被应用于吸收光谱技术中以提高检测灵敏度。在光声光谱气体检测中,以积分球气室作为吸收池,并在球上附加一根铝管作为共振腔,二者构成耦合声学系统。通过仿真与实验得到系统的实际共振频率,以此共振频率调制LED光源,气体受激产生光声信号;利用嵌入式技术,采集球上与铝管末端的两个微音器信号,并进行数据处理、分析、上传与显示。使用NO_(2)气体进行实验,对比实验结果,发现铝管末端的信号值可有效反演出NO_(2)气体浓度,最低检测浓度(体积分数)为3×10^(-6)。

Photoacoustic spectroscopy has been widely used in gas detection because of its high sensitivity,strong reliability,and fast response.Because the high-reflectivity coating on the inner walls of integrating spheres can greatly increase the optical path,integrating spheres are often adopted in absorption spectroscopy to improve detection sensitivity.In this paper,an integrating sphere is applied to gas detection by photoacoustic spectroscopy.With the integrating sphere gas cell as the absorption pool,an aluminum tube is attached to the sphere as a resonant cavity to form a coupled acoustic system.The actual resonance frequency of the system is obtained through simulations and experiments.At this frequency,the LED light source is modulated,and the gas is stimulated to generate photoacoustic signals.Embedded technology is integrated to collect the signals of the two microphones on the ball and at the end of the aluminum tube for data processing,analysis,uploading and display.NO_(2)gas is employed in the experiments and the experimental results show that the signal values at the end of the aluminum tube can effectively invert the NO_(2)gas concentration,and the minimum detection concentration(volume fraction)is 3×10^(-6).