Research On Gas-sensing Material Performance Testing System Based On Virtual Instrument

The process of industrialization has brought more and more air pollution to people’sliving environment, which also put forward higher requirements for gas detectiontechnology.The gas sensor is an important element to detect of harmful,toxic gases,and gassensing properties of the gas-sensing material determines the level of detection accuracy,so itbecomes the key to detect of gas atmospheres that accurate testing of the gas sensingproperties of the gas-sensitive material.With the development of computer control technology and software technology, Usecomputer software to build up a virtual measurement and control instruments are graduallyreplacing traditional instruments,and plays an increasingly important role in the field oflaboratory and industrial test. As a full-fledged virtual instrument platform, LabVIEWcontains a wealth of advanced mathematical analysis library, more intuitive in the way ofprogramming, contains a variety of interface which can be connected to different devices, ithelps to build the entire test system.This thesis presents a gas-sensitive material performance testing system based on virtualinstrument,the hardware of the system is consisted of data acquisition card and gas-sensingmaterial test circuit.In this thesis,introduces the development and classification of thegas-sensitive material,analyzes the sensing mechanism of the gas-sensitive material,describesthe main parameters and characteristics of the gas-sensitive material and the main factorsaffecting the gas-sensitive material characteristics. According to the actual test requirements,hardware part,we choose the PCI-1711multifunction data acquisition card which developedby Advantech Co.,and build a separate test circuit for each gas-sensitive material.Furthermore, take certain anti-interference measures.by analysising the possible interferenceof the hardware.Software part,we choose LabVIEW as development platform,control the dataacquisition module by setting the basic parameters;After experimental comparison,wedenoises the original signal by wavelet soft thresholding filtering;Use transient analysismethod to analyze the sensitivity curve,we obtainthe sensitivity, the response time andrecovery time of the gas-sensitive material; Analyze the effect which the heating voltageinfluences the gas sensing properties by Gaussian fitting,we obtain the best heatingvoltage;Analyze the gas selectivity by comparison of the sensitivity in the different gases.Experimental results show that the system can complete the inspection work accurately.Finally,the system carries out the actual detection in different conditions,such as different gasconcentrations, the incorporation of metal, the preparation process, different heating voltageand the different types of gas,achieves the detection tasks to the gas sensing properties of thegas-sensing material.