Study On Methane Detection System Based On Photoacoustic Spectrum

Photoacoustic effect is discovered by bell who is a American famous scientist in 1880.photoacoustic spectrometry is just based on the photoacoustic effect.But,in a long time,the study of photoacoustic effect is nearly halt.Till 1970s,because of intense xenon lamp,high sensitivity microphone and piezoelectricity chinaware detection apparatus coming out.Since 1980s,as a result of laser and weak electricity signal detection technology is high-speed developed,so as to photoacoustic spectrometry has the base to develop.Photoacoustic spectrometry with high selectivity and sensitivity is one of optimal facility for trace gas analysis.Gas detection based on Photoacoustic spectrometry has advantages as follows:Because of measuring gas absorption of light direct,so detection based on Photoacoustic spectrometry has very high accuracy and reliability.Nearly has not zero-drift,no gas,no signal.Due to its feature of selective absorption,so we can monitor many sorts of gas in a photoacoustic cell.Since acoustic detection is used instead of optical detection,enhancing the quality of detector,ensuring long-term stability,and making it no need to adjust and demarcate.High sensitivity,can reach 0.1ppm,even down to sub-ppb level.This paper applies photoacoustic spectrum to methane detection.Methane as greenhouse gas is estimated to contribute about 25 % to the'global warming'of the atmosphere.At the same time,gas(primary element is methane)accident is one of the primary causes of mine death.So,Whether for protecting entironment , circulating industrial mine safely,or for ensuring person safe,detecting concentration of methane accurately and in time has very important meaning.This paper totally includes seven chapters. The contents of the paper are as follows:The first chapter introduces history development process of photoacoustic spectrometry,new production in domain of photoacoustic spectrometry and feature and apply domain of photoacoustic spectrometry.The second chapter from gas molecules absorption theory,gives several characteristic absorption apex of methane,then selects 1330nm as the research object. Expatiates the Gas Filter Correlation spectrometry concretely, expounds the basic theory of gas detection based on Photoacoustic spectrometry...