Application Research On Methane Measurement Based On Infrared Technology And Spectrum Absorption

In China, the gas disaster has always been the great problem in the coal industry, which is a main factor restricting the coal mine safety production. Therefore, the real-time detection of the cause, leakage and concentration of gas plays a very important role on the safe operation of mining, personal safety and environmental protection. The gas detection technology based on spectral absorption is an important forefront topic in the research filed of gas detection technology now. The gas detection method, which uses light emitted diode or semiconductor laser as light resource, has multitude advantages over traditional approaches, such as high sensitivity, multiple selection, wide dynamic range, good ratio of signal to noise and quick response time.The methane is used as a research sample in this paper, which is the main component of mine gas. The academic base of gas measurement by absorption theory is described by analyzing the theory of gas infrared selective absorption. The mathematical model of gas concentration difference absorption measurement is built up and a gas measurement system based on spectrum absorption is developed.The experimental system uses a gas sensor structure with dual-wavelength and single optical path, selects the strong absorption spectral line of methane in 3.31μm wave length, uses a infrared LED as light source, realizes the gas concentration difference examination which uses the ratio of measuring signal and reference signal to eliminate the interference factors, such as the light power changing. According to the characteristic in the gas detection system, the light modulation circuit and the signal conditioning circuit are designed.ARM9 S3C2410, which is a microcomputer, is taken as the core of the instrument. The circuit design of power circuit, data storage, data acquisition and serial communication interface are completed in the system, and the functions are realized through programming with ARM9 S3C2410, which includes the collection of concentration information, the digital filter process and the data transmission. The methane concentration value and the alarm information are transmitted into the computer by asynchronous communication module USART1 and computer serial interface RS-232, which realizes the analysis and memory about the concentration information. Finally, the gas detection system is studied to verify the feasibility of the detection program. The output waveform and value are analyzed and processed. The results of experiments are shown in the end and the datas can basically meet the requirement of methane detection.