Online Methane Concentration Detector Based On The Arm

A Methane Concentration Detector that used espesically for early warning in the coal mine is introduced, which is based on the gas molecule’s absorbing infrared principle. The whole system use the NDIR technic and its MCU is STM32Single-chip Microcomputer with the ARM Cortex-M3core.the driving source is3.31μm wavelength impulsive infrared combined with4.00μm wavelength as the reference infrared, and also design an integrated hardware and software framework for the system. A bent pipe structure is designed for the system to effectively extend the light path, which can make the gas absorbed the infrared to the fullest extent, also intergrate the light source and pyroelectric sensor on the gas room to fix their relative position and so to reduce the instrumental error. Choose the appropriate optical filter for the sensor the make the "single light path-dual wavelength" results. Because the sensor’s output single is very weak,the filtering and amplify circuit designed to djust it to the voltage scope which is suitable for the MPU to deal with, the system is equipped with a liquid crystal display (LCD) to real-time display the methane concentration data and it also can connect a PC through the Serial to on line query and preserve the test data. For the softward proportion, the design methodology of module base applied to this software design, there will be very effective programming which controls the data collection and analysis, with the drive of STM32chip, the A/D convertion module use the way of multiple filtrate algorithm, multiple even filter and the forward integration to deal with data, with the result of substantially improve the A/D resolution and the final precision, the alarm set is written toEEPROM which made the data can be preserve during interruption of power supply.An inquiry language programming which embedded in the MPU will get the Detector well-prepared for detectting. By the way of using the collected data to fit a curve, which can reflect the relationship of the Methane Concentration and the test data, the software will calculate more intensive point to form a inquiry table, using which the inquiry program can deliver the concentraion data when testing.Experience show that the Methane Concentration Detector has the advantage of no easy to be poisoning or explode, it can Response very fast and has a low power and volume. Its biggest offset only0.286%and has a high sensitivity of100ppm, the response time is only25s, which have arrived prospective effect.