| Every gas has its own absorption spectrum, the resonating absorption is engendered while the wavelength of light-source beam is the same with the wavelength of gas absorption. The absorbing intensity is related to gas concentr- ation, gas concentration is detected according to measuring gas absorbing inten- sity. The experiment scheme is designed, and the methane detecting experiment research is carried out.Main topics:Some gas concentration detecting methods are analyzed and comparison, and absorption method is made sure as the theory method. Full research on the actuality of optical fiber gas sensor, new experiment scheme is attempted to rese- arch to high measuring precision and applicability.The gas molecule absorption line and methane gas absorption spectrum is analyzed; the Super Luminescent Diode is made as the system light source, the time-sharing difference is employed in the detecting system. The automatic temperature control circuit of SLD is designed.Gas cell which is made of two rectangular prisms is employed. The times of light beam going back and forth in the gas cell is determined by distance between planes of symmetry through respective apexes of the prisms. The sensitivity can be chosen by means of adjusting the distance.Taking the powerful software Visual C++ 6.0 as tool, using the rapid data processing function of computer, the real time online dynamic monitor software is designed based on User Interface., real-time and continuous detection are realized.By using the instrument and the condition of the laboratory, the experiment of the system is carried out, system sensitivity and resolving power and the calib-ration of the whole system. The results confirm the feasibility of the detecting system.
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