Study On Multi-Point Optical Fiber Methane Measurement System

In coal mine production, along with the exploitation of coal seam, usually gush methane. Clear fire will lead to gas explosion when the volume percent of methane reaches 3.5%~16%. So it is very important to monitor the density of methane in coal mine production, and sensor with high performance is essential to the automation and intellection of monitoring system of methane. Optical fiber gas sensing technology is a developing and novel technique, which has a wide applicable prospect in industrial production, environment monitoring and medical science because of its quality performance.In this paper, the basic principle of optical fiber sensor technology and the academic base of the gas absorption measurement theory are introduced. The absorption spectrum of methane is confirmed and the spectra characteristics which is fit for low-loss optical fiber to transmit a long way is also discussed. At the same time DSP technology and CAN technology are introduced. It makes a networked monitoring system using TMS320F240 and SJA1000 based on the analysis of DSP and CAN technology. It also makes profound analysis and research of the network made-up by DSP and CAN and computer.In term of the practical problem in our country's colliery, after overall and detailed analysis of developing tendency and reliability of the Mine Monitoring System, it puts forward a new method to institute Monitoring System. The communication network of equipment adopts CAN Field Bus, and its core is Digital Signal Processor, and its local monitoring equipment is optical fiber sensor.In this paper, methane is used as a research sample. The paper designs an all optical-fiber gas sensor based on near-infrared absorption spectrum method. Using SLED as the light source based on the theory of wide source difference absorption and harmonic detection,being combined with a weak signalmeasure circuit with the core of lock-in amplifier and the circuit of computer's control, the system is achieved to measure the concentration of methane. Using the instrument and the condition of laboratory, the experiment of the designed system is carried out. The experimental results confirm the feasibility of the measurement system.