Study And Development Of Gas Detecting Instruments For Coal Mine Application

Many kinds of inflammable and explosive (IAE) gases, such as methane and carbon monoxide, coexist in coal mines, which are the most dangerous sources leading to explosions. Those severe accidents happened in coal mines not only made huge economic loss but also endangered mineworkers' lives. In order to avoid explosion and to ensure the mineworkers' safety and health, it is important to quickly and correctly monitor the gas concentrations in coal mines. Much attention has been paid to study and develop such kind of detectors. The topic of this thesis is from the national S863 program funded project named as "the IAE gas detection microsystem" (No.2003AA404180), which is aimed to detect the two major inflammable and explosive gases in coal mines - methane, carbon monoxide and their mixtures simultaneously.Two kinds of intelligent instruments, using Artificial Neural Networks (ANN), are designed and developed to measure methane, carbon monoxide, and their mixtures. Both the instruments are mainly composed of eight modules, i.e. Gas Sensors, Heating Power Supply Circuit, Timer, Temperature and Humidity (TAH) Sensor, SCM, LCD, DataFlash, and Serial Interface. All gas sensors, and temperature sensors used in the instruments are fabricated by the 49th insititute of Chinese Electronics Technology Group Company, who is the cooperator of the S863 project. One of the instruments utilizes a gas sensor array in which each sensor is operated at constant temperatures. Another one uses only one gas sensor but its opearation temperature is modulated with heating pulse to reduce the power consumption.All sensors' responses are acquired through an A/D converter, and the MSP430F149-type 16 bits SCM is adopted as controller and calculator. The gas composition and concentration as well as ambient TAH are analyzed by MSP430F149 then displayed on the screen real-time. While the detected gas concentrations are over the warning level, light and beep alarm signals will be generated. The acquired data are saved into a dataflash AT45DB161B. In case of losing data due to power break, the saved data can be anew transferred to PC through a Serial Interface. Some exterior keys are also installed on the panel to set the alarm value, record signals or reset the system. In addition, the power consumption of the instruments is evaluated and methods to further reduce it are discussed.