Design Of Methane Detector Based On Infrared Spectrum Absorption

The methane detector is a main testing instrument for detecting methane concentration in the coal mine. Infrared spectrum absorption methane detector is a kind of methane detector which based on the theory that a gas has strong absorptive only for fixed wavelength of infrared light. Infrared spectrum absorption methane detector has high detection accuracy, short response time, non-toxic, no manual calibration and other characteristics.In the light of current situation and existing problems of the infrared methane detector, the thesis mainly researchs the following contents:Firstly, introduced the various methods used to detect methane concentration, and described their features, but also introduced the research status of infrared methane detector at home and abroad, while focusing on describing the principle of infrared methane detector.Secondly, studied the way of calculating the effective length of light path, and given the analog optical path diagram, while using the way of single-light beam and double wavelength, light source stability’s influence on the measuring result is eliminated, all above laid a foundation to accurately measure the concentration of the methane.Thirdly, in the aspect of circuit design, designed the light source drive circuit, the weak signal modulation circuit, amplifier and filter circuit, analog-digital conversion circuits, and sound and light alarm circuit; in the aspect of software design, designed the system initialization program, data collection and processing program and sound and light alarm drivers program, etc.Fourthly, the impact of temperature and pressure on the methane concentration detection is mainly studied, and, through experiment, the relational expression between methane concentration and voltage under different temperature has been given.