Research Of Infrared Carbon Monoxide Sensing System Based On Off-axis Integrated Cavity Output Spectroscopy

Carbon monoxide(CO)often appears in incomplete combustion and transportation gas pipelines during coal mining and coal heating.Due to its highly toxic characteristics,CO above a certain concentration can cause people to faint and even lose their lives.Therefore,in order to detect CO in time,this paper uses off-axis integrating cavity output spectroscopy technology,based on the principle of infrared gas absorption spectroscopy,using DFB lasers combined with optical resonators,and developing an infrared CO gas sensing system based on off-axis integrating cavity,using condensation dehumidification The pretreatment of the gas by the filter and the dust collector,the design of a temperature control circuit to control the temperature of the gas chamber,the study of the anti-interference of the system,the CO gas experiment,and the stability of the system.This article first introduces several commonly used infrared absorption spectroscopy gas detection technologies,expounds the advantages and disadvantages of different technologies,and introduces the domestic and foreign research progress of off-axis integrating cavity output spectroscopy technology.This article introduces the basic theories of infrared absorption spectroscopy,including molecular spectroscopy theory and Lambert Beer’s law,discusses the principles of absorption spectroscopy and commonly used absorption line types,and elaborates on the off-axis integrated cavity output spectroscopy technology.Then,based on the off-axis integrating cavity output spectrum technology and the principle of infrared absorption spectroscopy,an off-axis integrating cavity infrared sensing system was designed,using a DFB laser with a center wavelength of 1563 nm as the light source,and installing two mirrors with a reflectivity of 99.97%.A closed gas chamber is formed in the designed resonant cavity,the near-infrared photodiode is used to receive the light signal,the preamplifier,main amplifier and filter circuit are designed,the analog signal is collected by the data acquisition card,and displayed by the host computer Lab VIEW and control,thus constituting a complete sensing system,and testing the performance of the sensing system.In order to ensure the stability and reliability of the gas detection system,based on the actual environmental requirements,a gas processing system is designed,which is mainly divided into two parts: dust-proof and dehumidification module and temperature control circuit.The condenser is used to dehumidify the gas and the dust collector.To remove dust,design a temperature collection circuit to collect the temperature in the resonant cavity,use PID algorithm to control the power of the heating belt to stabilize the temperature in the resonant cavity at a set value,design a switch control circuit to control the power supply of each module,and use a communication module Communicate with the host computer,and test the dehumidification and temperature control performance.The system was integrated and the CO experiment was carried out.First,the light path was collimated by a red laser,and then the CO experiment was carried out with a DFB laser with a center wavelength of 1653 nm.The absorption signal amplitude of different concentrations was measured by the gas distribution system.Calibration and testing the stability of the system for a long time,explored the lower detection limit of the system,discussed the influence of Kalman filtering on the system performance,and tested the response time of the system.