Research On Toxic And Harmful Gas Telemetry Method Based On Infrared Multispectral

In traffic,substation,fire and other public safety emergencies,the leakage of toxic and harmful gases can not be completely avoided.The detection and identification of toxic and harmful gases is necessary.The toxic and harmful gas detection system not only provides the basis for rescue and protection,but also provides monitoring means for public environmental safety.In many toxic and harmful gas detection methods,passive infrared detection technology has the advantages of no sample preparation and remote real-time telemetry.At present,the passive infrared is mainly in the form of Fourier interferometer with ultra-high spectral resolution,which is expensive and limited in application scope,so it is difficult to promote in a large range.Therefore,it is of great significance to study a portable,low-cost and easy to expand passive infrared gas detection system.In this paper,based on the infrared characteristic spectrum and identification method of toxic and harmful gases,the separation band is selected for several kinds of common toxic and harmful gases,and a multispectral infrared passive telemetry system based on narrow band filter is developed.The laboratory designed and built the experimental device of gas passive telemetry system,used lock-in amplifier technology to improve the signal-to-noise ratio of the system,and used AC amplifier to suppress the infrared signal drift.For the chopping mode with active light source,the influence of chopper radiation can be ignored;When the chopper temperature is higher than the target temperature,the chopper radiation will be greater than the target radiation,resulting in the measurement signal amplitude inversion.This paper analyzes the cause of signal amplitude inversion,proposes the solution of phase-locked signal adaptive calibration,and uses MATLAB software to simulate the spectrum of three common toxic and harmful gases(ammonia,dichloromethane,dimethyl methylphosphonate(DMMP)).Radiation calibration experiments are carried out in the laboratory to verify the problem of signal amplitude inversion in theoretical analysis and the correctness of phase-locked signal adaptive calibration method.Using blackbody standard source and absorption cell to simulate the scene of gas leakage,the measured spectra of the above three gases are collected,and the results show that the simulated spectra are basically consistent with the measured spectra.The support vector machine(SVM)was used to identify the gases,and the laboratory and outdoor 50 remote sensing experiments were carried out.The results show that the detection limit concentrations of ammonia,dichloromethane and DMMP are 1365 mg/m3,1060 mg/m3 and 345 mg/m3,which can meet the requirements of remote sensing and identification of toxic and harmful gases.