| Gas detection plays an important role in industrial production, environmentalprotection, security check, aerospace, etc. However, its application has been limited byhigh prices. Therefore, this paper developed a low-cost WIFI wireless gas monitoringprobes, and a hand-held formaldehyde detector has been designed on this basis.Gas monitoring probes stressed the need to have a real-time online analysis, networkanalysis functions. The sensor array is the core of the probe, which directly affects theperformance of the entire test. A sensor array containing eight metal oxide semiconductorelements, with a size of7mm×5mm Ceramic plate, was prepared by using integratedcircuit method, which also integrated the functions of heating and temperaturemeasurement. In order to reduce the operating temperature of the sensitive material, wedesigned UV excitation circuit. The STC12C5A32S2, With A/D, D/A function and alarge EEPROM capacity, is the core of the signal processing section. It not only canrealize the traditional RS232communication, also can realize the WIFI wirelesscommunication, and transfer data wirelessly at a rate of54Mbps. It can use externalpower supply, and also be powered by battery. The whole equipment size is102mm x40mm x30mm. A hand-held formaldehyde detector is designed for the detection offormaldehyde gas based on the probe, which cost is within RMB200.The probe hardware is evaluated through testing the standard resistance. The resultsshow that it is suitable with resistance of gas sensor array between100-1G, and thetemperature resistance error is less than3%.In order to evaluate application performanceof the probe, we designed an environmental simulation chamber. It was showed thatoptimum operating temperature of this probe is75℃and the responding sensitivity for100ppm and1ppm formaldehyde can reach1802.03and14.7. Glacial acetic acid,benzene, ethanol, acetone were tested respectively with100ppm at75℃, it was proved that the probe has good selectivity. |
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