Dissertation For The Master Degree In Engineering

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 recent years, with the development of optical fiber sensing technology, the research of optical fiber gas sensor has been seriously regarded all over the world. The signal detected by optical fiber gas sensors is carried by light wave, which has no influence on the measured object. The sensor that has good independence performance itself can be adapted to all kinds of surroundings. The optical fiber sensing system with the sensors, which can be connected with computers conveniently, can realize many functions request and intellectualized need. They can match with remote measure technology to measure and control in long distance.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, in which The communication network of equipment adopts CAN Field Bus, and its core is Digital Signal Processor, and the serial communication network between the monitoring module and computer adopts telephone network by way of Modem .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 signal measure circuit with the core of lock-in amplifier and the circuit of computer's control, the system is achieved to measure the concentration. 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 measure system.