Based On Field Bus Technology, Gas Detection And Alarm System

The system of methane measurement and alarm based on PCS is introduced in this paper .The practice problems about the methane measurement in the mine are comprehensively discussed. We have resolved the problems as following. First, the development of communication controller of PCS. Second, the problems of long-distance data communication, signal attenuation, interference from outside in the measurement system. Third, the development of intelligent instruments possessed auto-demarcated function.The whole system regards supervise PC as the center, which joins the Field Bus by communication Controller. Every of the intelligent instruments directly connected with Field Bus as a node. The data from the supervise PC is transmitted to the intelligent instruments through Field Bus. The measurement data from the intelligent instruments can be transmitted to the supervise PC also through Field bus. As a network bridge, communication controller is the interface device which realize the function of communication between supervise PC and Field Bus. The Field Bus is a pair of twisted-wire which extended to some measurement spot in different layer of the mine, because of the long-distance between the dispute spots. The signal is modulated and demodulated when it is transmitted. We take some measures such as anti-jamming and rejection of attenuation to make sure of reliability of communication.Each of the intelligent instruments possessed the independent measure function is connected with the Field Bus. Also, they have the interface of digitalcommunication, keyboard input and digital display. The sensor MCI 12 is applied in each of the intelligent instrument. In order to reject the drift of output characteristic because of the long-time work, the method of auto-demarcated is applied in the intelligent instruments. The measurement precision of the system is improved when the method is applied.