Research Of IR-absorbing Gas Detection System Based On DSP

With the fast development of mining industry and the continuous increasing consumption on coal in China, the real-time detection of the concentration of gas becomes more and more important to ensure sustainable development of Chinese coal and safety of coal industry. IR technique is one of the most active areas that researches into the real-time detection of the concentration of Methane. At the present time, because of the costliness for the foreign manufactures and shortcoming for the domestic ones, a more high sensitivity and high stability and real-time IR-absorbing gas detecting system is needed.Due to the absorption to IR radiation at a characteristic wavelength, and the relationship between the absorption intensity and the concentration of methane, the real-time IR-absorbing methane detecting system was designed and set up. The IR absorption intensity, which is recorded in the form of voltage signal, was used to calculate the concentration of methane with a digital processor.A sensor-IR32BC was used as the probe and TMS320LF2407 DSP (TI Company) as the core processor. According to the character of the IR32BC and the surroundings of the coal mine, the suitable light source modulation circuit and the weak signal handling circuit were designed. The ability of the concentration of Methane recording, digital filtering and concentration calculation etc were realized by them. In order to achieve the high stability and high sensitivity and real-time detection of Methane concentration, this paper improved filtering means of weak gas signal and combined with simulation circuit filtering and digital filtering, thus, realizing more fully filtering. Some essential interface circuits and corresponding algorithm routine and program for modules were also designed. The topics included the LCD display module, the surrounding temperature monitoring module, data storage module, 485 communication module and alarmmodule. The concentration of Methane was real-time displayed with the LCD steadily and sensitively. The alarm module would work while the detected concentration was over a given value. EEPROM was used to storage warning limit of concentration and real-time concentrations once the power was broken. RS-485 were used to improve the ability and distance of communication.