Research Of Infrared Methane Detection Device Based On Embedded WinCE System

This dissertation is originated from the national natural science funds project that research on “Under the deep mining of infrared gas sensing properties change model and adaptive detection mechanism research”, the project number is 61307124.As the major energy source, the demand of coal is increasing with the development. In the process of coal mining, the gas disaster is one of the five natural disasters which are serious threats to coal mine production safety. Every year, about thousands of people lost their lives as a result of coal mine gas explosion. As the main ingredient of gas, when the concentration is at range of 5.3% to 15% vol methane will explode under accompanied by a certain concentration of oxygen and heat-induced which seriously threaten people’s lives and property safety. Therefore, an accurate and fast measurement to the concentration of methane is of great significance, and it is an urgent problem to be solved in coal mine safety production.In this paper, based on infrared absorption spectroscopy technology, a selected dual-channel NDIR sensor combined with an embedded WinCE(Windows Embedded Compact) system was used to design and implement a portable methane detector. The detector mainly includes three parts which are sensor and signal processing circuit, embedded WinCE hardware/software system and signal processing platform based on Lab VIEW. Firstly, a sensor driving circuit and signal processing circuit were designed targeting the selected British E2V’s IR12 GJ integrated infrared sensor. The sensor has two output channels which are measurement channel and reference channel respectively. Through the signal processing circuit, two output signals can be amplified, DC blocked and adjusted and so on.Secondly, the two output signals after adjustment were collected by USB DAQ(Data Acquisition) Card and transferred to the embedded system based on Lab VIEW software platform for the further processes. As the core, the DSP(Digital Singnal Processing) processor(S3C6410) was used to designed the required embedded hardware system platform, including the selected DSP core board, designed USB host ports, serials ports, SD card interface, ethernet port, wireless communication module and buzzer etc. Thirdly, the signal processing platform is designed whose main functions are signals collection, relative filter processing to the two collected output signals, extraction of the corresponding amplitude, gas concentration calculation according to the relative formula, concentration display and data storage. Finally, if the measured concentration is excessive the sound and light alarm are executed. The LabVIEW program is converted through Touch Panel Module, and the converted executable file was ported into the embedded WinCE system. The methane gas experiment was carried out and the results show that: the LoD(limit of the detection) of this detector is 100 ppm; the relative error is less than 9.1% at the range of 100 ppm to 65000 ppm; for the gas sample with the concentration of 5000 ppm, 90 minutes measurement was carried out, the max relative error is 8.3% which indicates excellent stability; for gas sample with concentration of 0 ppm, 90 minutes measurement was carried out, the result is analyzed by Allan variance, when the integration time is 31 s the forecast limit of detection is 17.58 ppm; and the response time is less than 20 s. This detector has advantages like small size and low cost, and shows promotion and application value because the selected sensor is suitable for mine circumstance.Innovation points of this paper:1. Embedded WinCE system is used in a portable detector and the intelligent andfunctional diversification are realized.2. The PC software LabVIEW is ported into an embedded system which realizesa powerful data processing capability.