The Design And Realization Of Infrared Methane Detector Based On MSP430MCU

Methane is common gas in the petroleum, natural-gas and coal exploration.In recent years, with the rapid development of the national industry, agricultureand other industries, the social demand for these energy increases with everypassing day. In the process of energy exploitation, safety accidents related tomethane gas have occurred. Therefore, it has very important significance for theresearch work of methane gas detection. Measuring the concentration ofmethane gas in a timely and accurately, it plays a very important role to ensurethe safety of industrial production, people’s life and property.At present, the more advanced detection method at home and abroad is tomeasure the concentration of methane gas by infrared absorption principle. Thismethod overcomes some shortcomings of the traditional detection methods, suchas easily be wrong, narrow detection scope, large measuring error and the needfor frequent calibration etc. It also has some other advantage, such as fastresponse speed, good selectivity, good stability, long service life and wideapplication range and so on. Therefore, this paper has developed a methane gasconcentration detector based on the infrared absorption principle. According to the absorption characteristics of methane to infrared light, thisdetector selected the3.31μm wavelength to measure methane gas concentration.In order to eliminate the influence of interference factors of external and system,the detector used the differential detection method to eliminate the measurementerror of methane concentration. After making a more detailed presentation andcomparison to two basic methods of the difference method, considering from thecomplexity and cost of the detector’s structure, this paper chooses dualwavelength single optical path difference method as the basic method ofmethane gas concentration detection. On this basis, this paper developed amethane detection instrument with MSP430single chip computer as the core,which includes hardware part design and software part design. The MSP430microcontrollers has some advantages, such as very low power consumption,rich on-chip peripherals, system stability and so on, selection model is theMSP430F1611microcontroller for this detector.The hardware design mainly includes the optical measuring part and thecircuit design part. The optical measurement is mainly composed of an infraredlight source, prober and a gas chamber etc. According performance requirementsof the detector to the infrared light source and prober, this paper respectivelyselected IRL715and PYS3228as the light source and prober of this detector,and do the corresponding design for the gas chamber. According to thecharacteristics of the selected infrared light source and prober, respectivelydesigned the corresponding source voltage drive circuit and amplifying filter circuit, and did some analysis for their characteristics.The software part design adopted the modular design method, mainlyincludes the data acquisition and processing module of signal, concentrationretrieval algorithm module, serial communication module of the system, and thecomputer software design module. This paper focused on introducing theprinciples and the design enablement of the median filter and FIR low-pass filter,and simulation analysis the effect of the FIR low-pass filter. Meanwhile, detailedintroduced the principle of commonly used Concentration Retrieval Algorithm(look-up table method, the polynomial interpolation and polynomial fittingmethod), and analyzed their respective characteristics, designed an objectivepiecewise curve fitting methods. In addition, this paper also focused on thecommunication implementation between MCU and E2PROM, and betweenMCU and computer. According to the selected E2PROM model (AT24C02) andthe characteristics of the interface standard used (RS-232serial), respectivelydesigned the corresponding interface circuit, and according to thecommunication protocol which they used to design the correspondingcommunication program, to achieve the communication between each other. Inorder to easily monitor the measured gas concentration and facilitate dataprocessing, the paper also written the PC software with specific function byusing VB MSComm control.Finally, this paper did performance test for the prototype under laboratoryconditions. The experimental results show that the detector has high accuracy, response speed and stability, and can meet certain production requirements. Atthe same time, according to the characteristics of the design methods and thecomponents used, the detector also has a high cost performance and relativelybroad market prospects. Its detection method also has certain referencemeanings to the research of other similar gas detector.