Develonent Of Infrared Sensor System Of Methane Based On Reflective Optical Model

At present, coal resources are the main energy in China. Methane gas is the main component produced in the mining. The work of safe production of state was never loosen and ignored, but the safe accidents of gas explosion in coal mine was never interrupted.Although methane gas is not a major component of the atmosphere, its impact on the greenhouse effect caused by carbon dioxide was larger. From the perspective of environmental protection or safe production, accurate real-time detection of methane gas was very important.In order to grasp the current research trends and progress, some research job on infrared detection technology at home and abroad was been done. Since the late 1970 s, some European scholars have used the method of absorption spectroscopy to monitor air pollution.Then there were researchers using IR theory, ellipsoidal optical chamber, thermal optical element, optimizing the layout of the detector, signal conditioning, the laser transmitter and other aspects to do some study. As a result, they achieved significant progress and made the laboratory techniques changed to industrial application. Domestic infrared detection technology started late, but developed rapidly. Their study made some progress, such as the optical absorption cell, multi-angle light signals, the detection system and the theory of molecular spectroscopy, but there was a gap to reach the industrial applications. From the theoretical point of molecular spectroscopy, infrared detection of methane gas was analyzed theoretically. On the basis of the theory, we use HITRAN Database to simulate IR spectra of gas molecules in the air. Furthermore, theoretically infrared technology was obtained todetect the feasibility of methane gas. For Lambert-Beer law, there are three detection problems, which were the absorption cross section of proposed coefficient, the optical path length and accurately measuring the intensity of light. Through a series of theoretical analysis and feasibility studies, the model of the reflected light of infrared methane sensor was established.Based on the model and existing sensing probe, we designed the entire sensor main circuit board, which was responsible for the power supply and provided voltage conversion circuit. And then a sensing probe interface circuit, processing weak amplifying the signal filter circuit, JTAG interface circuit debugging interface were designed. After the completion of welding the circuit board, the performance analysis and comparison of signal processing circuit were researched.For calibration experiments, a calibration experiment platform was build. We use 1-Wire bus communication protocol calibration to test data writing and read DS2431 chip. On the basis of former, calculation of the concentration module based on single-chip was designed and then experimental test was done.In the experimental test on the basis of exclusion of other interference, effect of temperature on the maximum sensor accuracy was obtained. Based on heat transfer theory,the optical chamber has been analysis simulation in conduction, convection thermal, and proposed practical temperature compensation calculations algorithm. The experimental verification: the algorithm achieved high accuracy and stability compared to the previous uncompensated within the concentration range of 0-4%.