Study On Detection System Of Carbon Dioxide On Photoacoustic Spectrum

There are huge kinds of volatile organic compounds(VOCs).However normal detection using optical spectra is effective for only few kinds of VOCs.Carbon dioxide(C02)is the main product of various VOCs after combustion.It is intuitionistic that total volatile organic compounds(TVOCs)concentrations can be obtained indirectly.Photoacoustic spectrum is one emering optical detection technology with high sensitivity to detect trace gas.It has the advantages of good selectivity,short response time and large dynamic detection range.It is an ideal method to realize trace gas real-time monitoring and is widely used in research and practical applications.In this thesis,we introduced the basic principle of gas photoacoustic spectrum from the theory of gas absorption spectroscopy.The relationship between photoacoustic signal and light intensity,gas absorption coefficient and gas concentration is experimentally investigated,which lays the foundation for gas photoacoustic spectroscopy.According to the characteristics of gas absorption line selection principle,we selected the 1572.66nm as center wavelength of the C02 gas,made photoacoustic cell on the premise that try to reduce noise,and constructed gas photoacoustic spectrum detection platform based on the tunable laser.We analyze the CO2 gas absorption coefficient and spectral line type,and discuss respectively the relationship with temperature and pressure.It shows that the peak absorption coefficient and the line width of the gas are closely related to the pressure and temperature.We study the relationship between the photoacoustic signal,the laser power and the gas concentration of C02 gas.The results show that the photoacoustic signal increases linearly with the increase of laser power and gas concentration when the gas does not saturate.