Research And Design Of Non-dispersive Infrared Detector For CH₄ Concentration

CH4 plays an important role in atmospheric chemistry and greenhouse effect.However,in various types of mine accidents,the probability of occurrence of mine accidents caused by gas explosion is the highest.CH4 is a combustible gas,CH4 and oxygen in the air will be come to pass chemical reaction when oxygen at a certain concentration ratio of the air,partial pressure of air would be lower.This phenomenon can cause people to hypoxia asphyxia and even death.CH4 does not support combustion,but when CH4 volume fraction in the air to 5%-15%ignited will explode,CH4 volume fraction of more than 9.5%explosion the strongest.Therefore,the detection of methane on the daily life of not only environmental protection has a very important significance.A new CH4 concentration detection system based on non-spectral infrared was designed,which is mainly used to detect CH4 in underground mine.Under this goal to complete the entire system include hardware and soft design,produce,debug,experiment and the concentration of the relevant experiments.The main contents are as follows:Based on the Lambert-Beer law,Chose IRL715 as the suitable infrared light source and chose the PYS3228G5.2/G20 pyroelectric infrared detector designed by PK Company,after analysis of the appropriate choice of light source modulation method.Design a new Non-spectral Infrared CH4 Concentration Detection System.Then,according to the hardware requirements,Design light source drive circuit,MCU power supply circuit,signal amplification circuit,USB to serial module circuit,liquid crystal display circuit and GPRS data wireless transmission module circuit.Use MSP430F169 single-chip write code of C language in the IAREW430 integrated environment for signal acquisition,filtering,data processing and so on.On the basis of completing the whole circuit and software design,the methane concentration detector is calibrated,making a large number of experiments and when this research’s rang is 0-4%,the maximum absolute error of the instrument less than 0.2%,relative standard deviation in repetitive experiment less than 3%,the resp(onse time is less than 15s.