Study On Gas Detection System Of Carbon Monoxide And Hydrogen Sulfide Based On Sensor Array

Abstract:With the rapid development of industries such as petroleum, chemical industry, coal and automobile, Environmental pollution is increasingly serious and the condition of environmental gas is getting more and more attention. The dangers of environmental pollution have threatened the survival and life of mankind. So the study of toxic gas detection has important theoretical significance and application prospects for environmental control and monitoring etc. Carbon monoxide and hydrogen sulfide are toxic gases which are common and have great harm. The traditional methods based on single sensor often require many sets of instruments to detect their mixed gas. The electronic noses based on sensor array have complex structures and are expensive. So they are very difficult to spread. Therefore, in this paper a gas detection system based on sensor array is designed, which can detect the concentration of CO and H2S in the mixed gases.Through the analysis of the sensitive features of single gas sensor, the CO and H2S detection system based on sensor array was designed. The system uses AT89C51as control core and uses the sensor array composed of MQ135, MQ136and TGS2602to collect signal from the mixed gases. Then connect the voltage following circuit composed of operational amplifier LM324. After A/D converter TLC2543converting analog signals into digital signals, the signal is input to the MCU and taken digital filter and noise reduction processing. The MCU makes the communication connection with PC through serial communication interface. In the PC using Lab VIEW to design the PC software to realizes the data display, storage and analysis. In the end, use BP neural network algorithm to deal with the data. The system uses a cross method of single sensitivity and multi sensibility of sensors. Gas qualitative identification step is omitted and the type and the concentration of toxic gases can be directly detected which makes the system structure simple.According to the software requirements and modular program design thought, the MCU software and the PC software of the gas detection system are designed. The MCU software is used to support the hardware system, realized by C language and complete the control, computing, I/O operations and communications. The PC software is realized by Lab VIEW and includes a graphical user interface which can conveniently control the MCU system and realize receiving data, graphical displaying data, processing data, and other functions. Each module is independently developed and debugged and combined according to the system’s overall framework and the relationship of modules. It enhances the system’s portability, scalability and maintainability.The gas detection system is controlled in real-time by a computer and the experiment verification is done after the corresponding hardware and software design. The system circuit can work properly and the training success of BP neural network proves that the design is feasible and reasonable. The adopted hardware structure based on the MCU can be used as a test platform of electronic nose and other gas sensor technology research. It also can be perfected and be practical products.