The Signalacquisition Of Air Quality Monitoring System

In recent years, with the rapid development of China’s industry, commerce and otherundertakings, chemicals, pharmaceuticals and other new synthetic products are constantlyintroduced, and some infrastructures such as city sewage treatment plants as well as garbagetreatment plants are continuously constructed, causing the air environment that we rely on tosurvive has become worse and worse, and city odor pollution occurs frequently, which affectsresidents’ normal life. Consequently, developing an intelligent air quality monitoring systemwhich can reflect the true state of environmental pollution and has good real-time performanceand high reliability has a very realistic significance.Based on the electronic nose technology, the topic has been completed the signal acquisitionand preprocessing of an air quality monitoring system, which is directed against the mixedmalodorous gases. By reading literature and a lot of research work, the overall structureframework of the system is determined: upper computer—lower computer.C8051F020single chip microcomputer is used as the core of the lower computer, who isapplied to collect the signal of sensors and realize the temperature and humidity compensation aswell as other related auxiliary control functions. The core of the upper computer is industrial PCand it realizes the virtual instrument through LabVIEW programming. There exist mainly twofunctions in the upper machine: firstly, the signal processing and separation, including complexsignal pattern recognition; secondly, providing a good man-machine interface and realizing thecontrol and display of collecting. The serial port is applied to realize data communicationbetween upper computer and lower computer.In addition to the hardware circuit, the necessary gas path part of gas gathering process isalso introduced in the system. The working process of gas path is demonstrated explicitly, andsome of the key devices are briefly introduced.The system has been studied the working principles and application performance of all kindsof gas sensors in depth. According to the requirement of the system, five different gas sensorswith large cross response constituting a sensor array are selected to collect the mixed malodorous gas.The signal conditioning circuit of each sensor is determined, the testing result of the chosensensor array under different sample conditions are analyzed through abundant preliminaryexperiments, which provide a proof to the final destination—the quantitative monitoring ofmixed malodorous gases.The testing result of the system will be presented based on the mature and wildly usedmethod of artificial olfactory discrimination in the thesis, which is to implement the consistencyof the two detection methods.The sampling experiments show that the system has good repeatability, high stability,convenient sampling process as well as easy to operate. Both the reliability and real-timeperformance can meet the requirements of the subject. This system has a wide applicationprospect and important innovative value.