Research And Design Of Portable Infrared Methane Detection Device

In our country, the coal is always the important energy, coal mining is animportant industry. But, there are so many factors affecting the safety of coalmining, including gas explosion, underground flooding and fire, the gasexplosion is one of the most serious accidents in coal mining. It has accountedfor more than80%in coal mining accidents; every year there were thousands ofpeople dead in coal mining accidents, the situation of safety production incoalmine is still very severe. Therefore, if we can monitor and warn theconcentration of gas in mine accurately and timely, it will play a very importantrole in coalmine production safety and personal safety.With the rapid development of technology, there are various types ofsensor used for methane detection in the markets, mainly including the typesof catalytic combustion in carrier, semiconductor of gas sensitive and opticalinterference and infrared spectrum absorption. Due to the flaws of thedetection principle and manufacturing process，The traditional gas sensorshave been unable to meet the requirements for accurate detection of methane concentration in complicated environment of coalmine. They have the flawsof narrow scope, easy to be poisoned, frequent adjustment, and short life.Infrared methane sensor can overcome the flaws effectively. It can detect thegas concentration accurately and provide a powerful guarantee for theproduction of coal mine.As a new generation of gas sensor，Infrared methane sensor has theadvantages of good selectivity, wide measuring range, high precision, fastreaction speed, long life, and so on.Based on innovation, a design scheme of portable infrared methane sensorwas proposed the paper, and several key issues were solved. The MSP430F1611microcontroller was used as the core controller. To make the sensor achievehigh precision, miniaturization and low power, the design of hardware andsoftware of the sensor were completed, the experiment was tested, and theanalysis and error compensation were made.The main work of research and design in this paper: Firstly, according tothe principle of infrared absorption, high performance infrared light source andpyro-electric detector were selected. According to the layout of devices in thegas chamber, the infrared optical chamber was designed and simulated, the typeand parameters of the gas chamber were determined finally based on the designprinciple of portable instrument.Secondly, designing hardware circuit, including the source modulation circuit; the signal conditioning circuit; with a microcontroller, the circuits ofdigital display, keyboard, sound and light alarm were designed. The circuitswere simple, suitable for portable devices.Thirdly, designing the software, with the method of modular programming,the work flows of light source modulation, data sampling and conversion,keyboard, and digital display.Finally, experimental test，data processing and analysis. A simple andeffective calibration scheme of methane was designed. Different concentrationsof methane gas were used to calibrate and measure the sensors. Through a largenumber of repeated experiments and the analysis of experimental data, the curvefitting and inverse calculation formula of concentration were got by using thesegmented least square method. In addition, interference factors in practicalwork for methane sensor were analyzed.