Intelligent Wireless Gas Sensor Is Developed

The gas explosion is one of the significant factors in coal mine security accidents, and it has caused the heavy losses for national and the people's life and the properties. Therefore, it is important to carry on the methane real-time monitoring in coal mine production safety system. If the methane detection is to be carried out dynamically and continuously, the intellectualized and wireless methane sensor is the essential condition.The support catalytic methane sensor has been widely used in methane monitoring system of coal mine because of its excellence qualities of high sensitivity, large range of measurement, wide range of frequency response, small volume and so on. But the existing support catalytic methane sensor has the disadvantages of "zero drifting" and serious nonlinear error affected by temperature. These disadvantages have influenced measuring accuracy of the sensor. Improved BP neural network has excellence capability for nonlinear approximation, and is widely selected to achieve nonlinear correction for sensor. ZigBee is a low complexity, low power consumption, low cost, low data rate, short range two-way wireless communication technology, and by this technology wireless transmission for sensor data is achieved. By integrating computer processing technology and ZigBee wireless communication technology, the intelligent and wireless methane sensor with merits of good work stability and multifunction is designed in this thesis based on the existing methane sensor. The main contents to be studied are shown as following:Methane sensor detecting principle is studied. The support catalytic methane sensor is selected as the sensing unit of the intelligent and wireless sensor. SCM (Single Chip Micyoco) is used to intelligently adjust "zero drifting". The advanced BP neural network method is used to proofread the nonlinearity of the sensor, and the BP algorithm is improved. The computation rules and the error back propagation transition are studied in this paper. Then the detailed procedure is generalized. And the program flowchart is draw. The improved BP neural network with one input layer, one hidden layer and one output layer is designed, and through the simulation experiment in computer for the measurement data, this method has achieved anticipated compensates. And the simulation results for the measurement data are given.The wireless communication technologies of ZigBee, Bluetooth, and WiFi are compared, and ZigBee is selected as the communication method for intelligent sensor. Then, the technology advantages of ZigBee are studied in depth. The functional diagram and the operation principle of MC9S08GT60 and MC13193 made in Freescale are studied in this paper. Based on the studies, the ZigBee module is designed, and the hardware platform for wireless communication between two intelligent sensors is created. Next, the sensor signal conditioner circuit and the interface for methane sensor and ZigBee module are designed, and this intelligent wireless methane sensor is realized. Low power of operate mode for the sensor is designed in particular.The whole diagram in hardware of the intelligent wireless methane sensor is given, and in software the whole flowchart and the communication flowchart between two sensor is draw. The simulation results of the nonlinear correction for methane sensor are integrated, and are stored in the Flash of SCM in the form of table. Then the wireless communication between two sensors is realized by serial debugging tool in PC.