Research On CO Concentration Detection System Based On TDLAS

Safety production in underground mines has always been a concern.People are increasingly demanding the accuracy of gas monitoring and monitoring components are more and more comprehensive.As a toxic,flamrmable and explosive gas,CO monitoring has gradually become necessary.Based on Tunable Diode Laser Absorption Spectroscopy(TDLAS)technology,a low concentration CO laser analyzer is developed and optimize'd in this paper by using mid-infrared DFB laser combined with photodetector,gas absorption cell and digital lock-in amplifier.This article mainly studied the following:Firstly,the spectrum theory of tunable semiconductor laser absorbing gas is analyzed.The theory includes basic knowledge of absorption spectra of gas molecules,Lambert-Beer law,direct absorption spectroscopy technology and calibration-free wavelength modulation technology.The mid-infrared absorption peaks of carbon monoxide were compared.Secondly,the hardware of the CO gas concentration detection instrument is designed,including laser driver digital lock-in amplifier,analysis and selection of the gas absorption cell and the photoelectric laser detector.The lower computer of the instrument and human-computer interaction software based on the touch screen are designed.Thirdly,the performance of the instrument was tested,?The influence of temperature and pressure on the measurement results of gas concentration was observed experimentally,and the data were corrected by polynom,ial fitting method.By comparing the absorption spectra of carbon monoxide in near infrared and mid-infrared spectra,the lower detection limit spectra are selected and a laser carbon monoxide detection instrument is designed in this paper.By analyzing the characteristics of the instrument,the measurement results of gas concentration changes caused by temperature and gas pressure changes are corrected.It makes the instrument more accrurate in detecting gas concentrations.