Research On Key Technologies Of Photoacoustic Gas Detection

Photoacoustic effect gas detection is a high precision measurement of gas concentration based on photoacoustic spectroscopy(PAS).The acoustic signal is excited because the gas molecules absorb the modulated light energy in the characteristic absorption spectrum,and gas concentration can be measured by detecting acoustic signals.Photoacoustic effect gas detection has the advantages of high sensitivity,no damage to the original properties of the test object,and a wide range of detectable spectrum,which can be applied to almost all types of samples.For this reason it is widespread concern various research areas of physics,chemistry,biology,medicine and environmental protection.This paper focuses on the photoacoustic effect gas detection technology and has carried out the following work:Firstly,the research significance and purpose of photoacoustic effect gas detection are introduced,and the research status of photoacoustic effect gas detection at home and abroad is summarized.The generation mechanism of gas photoacoustic effect,technology and instrument used in photoacoustic signal detection system are elaborated.The theories of gas molecule absorption spectrum,absorption of light energy,sound wave excitation,and wavelength modulation are introduced,which will provide a theoretical basis for the realization of photoacoustic effect gas detection based on photoacoustic spectroscopy.Secondly,An extrinsic F-P acoustic sensor based on the structure of fiber end-membrane is designed and manufactured.The acoustic sensor,which made of different diaphragm materials,are measured by experiment.The results show that the sensors made of gold film,silver film,copper film,zinc alloy film,and micro-grid carbon support film exhibit a good linear response property.The sensor made of gold film can detect the minimum acoustic signal with a slightly higher sensitivity,and the natural frequency of the circular diaphragm is calculated by simulation software.Finally,the finite element methodt is used to simulate the cylindrical photoacoustic cell.The amplification of the acoustic signal by the resonant photoacoustic cell and the sound field energy distribution at the resonant frequency were obtained through calculation.By optimizing the length and radius of the photoacoustic cavity,the acoustic resonance frequencies of the photoacoustic cells of different sizes are calculated.The change of the resonance frequency of the photoacoustic cell under different sizes is calculated,which provides a basis for the production of the photoacoustic cell and the installation of the acoustic sensor.In the photoacoustic effect gas detection technology,an acoustic sensor and a photoacoustic cell are important components for detecting weak photoacoustic signals,which are directly related to the limit sensitivity of the gas concentration detection system.It is of great significance for the study of acoustic sensors and photoacoustic cell.