Research And Design Of Electronic Nose System Based On S_nO₂ Gas Sensors Array

With the development of sensor, electronics, computer and pattern recognition technology, the application fields of electronic nose systems are being more and more widespread and also receiving a more universal attention. Electronic nose's applications have penetrated into quality control, environmental protection, national security, fire control, automobile, aerospace, disease diagnostics and industrial process control and other fields. Research and implementation of electronic nose system of low-cost, high accuracy, high integration and commercialization can make up the shortcomings of operation complicated, bulky, poor portability, high cost and no real-time automatic monitoring of traditional gas detection methods (such as gas chromatography).With analyzing the principles and characteristics of electronic nose system, the paper puts forward the overall technical solution of electronic nose system using BP neural network as the pattern recognition. According to the theory of BP neural network used in electronic nose systems, system uses the MSP430 microprocessor controller as subordinate computer to complete A/D conversion, data storage, RS232 serial communication, LCD display, and interpersonal interaction, and also uses PC as host computer to complete data acquisition, pattern recognition. On the basis of the overall solution, paper also designs hardware circuits and the software of E2PROM, RS232, LCD display, system power, keyboard and others, all these parts can work together under the control of MSP430, and gives realization of the hardware circuits and program flow of the software. Considering the larger power consumption of gas sensors array, paper designs the heating control circuits with constant 5V and 15W maximum output power. And paper also designs signal measurement, amplification and analog-digital conversion circuits. According to the characteristics of electronic nose using BP network, paper designs host computer software and BP network pattern recognition algorithms, and gives the system's functional test's results.At the end of the paper, the experimental results of single gas's qualitative analysis and quantitative calculation using developed system shows that BP network pattern recognition algorithm applied to electronic nose system is feasible, and able to achieve the desired results. Paper also researches key factors which affect the performance and train of BP network. In addition, the system has a certain degree of generality for electronic nose system which using sensor arrays and BP network pattern recognition algorithm.