Research On Methane Sensor Based On Multi-pass Cavity

It is gas calamity that imperils the safety of mining industry in our country. It has been the most serious matter which restricts the development of the mining industry. In mining exploitation, hidden trouble in safety has increased gradually. It can not be ignored that the ratio of gas accident to whole mining accident has increased gradually. So, detecting the origin, leak and density of methane (the main component of gas) in time is crucial to the safety of mining industry and personal security and safety.In this dissertation, the sensor technology that is based on absorption spectrum and optical resonator are integrated together. The theory about optical intensity and gas density are used to design absorption cavity of methane sensor that is based on multi-pass cavity. The absorption cavity can improve or even replace traditional absorption cell that is much bigger because of low heat dispersion. The dimension of this absorption cavity is less than the previous, at the same time absorption cavity dose not bothered by the question of heat dispersion. This is the innovative design of the dissertation. Simple structure, high stability, high detecting precision and low environmental affect give the absorption cavity the advantage. And the absorption cavity is also antielectromagnetic, non-pollution, energy saving. Compare with other optical methane sensor, the most attractive advantage of this absorption cavity is that its dimension is less than the others so it can be a kind of portable optical methane sensor rather than only working in the laboratory.According to the Beer-Lamber law and absorption spectrum of methane, a kind of communication light-emitting diode (LED) used widely now is chose to use in the design of this dissertation. Using this kind of LED can reduce the cost of the sensor and can also make design feasible. According to differential detecting method, the design also adopt the two wavelength-one path differential detecting structure to reduce the affect caused by instability of LED and excursion of photoelectric components and improve the precision of detecting the density of methane.