【正文】 gration technology, and some nanomaterials The application of electronic nose will have broad application prospects. Many different types of the electronic nose, the typical working program that is: 1) Sensor initialization: using a vacuum pump to the air sampling lessons to small containers fitted with the electronic sensor array chamber。 2) Determination of the sample and data analysis: sampling operation unit the initialization of the sensor array is exposed to the odor body, when the contact with the surface of the active material of the volatile pounds (VOC) and the sensor (ultrasonic sensor), to produce the transient response. Such a response is recorded and transmitted to the signal processing unit for analysis, and stored in the database of a large number of VOC pattern parison, identification, and to determine the type of odor。 3) cleaning the sensor: measured after the sample is finished, use of alcohol vapor flush . The sensor surface of the active material, the odor removal measured Bi mixture. In enter new measurement prior to the next round, 無(wú)錫科技職業(yè)學(xué)院科技 論文 The application of electronic nose 4 the sensor still implement initialization (that is, between the work again, each sensor are required dry air or some other reference gas cleaning to meet the benchmarks). The measured odor effect of time is called the response time and the purge process and the reference gas role of the sensor array used in the initialization process time is called the recovery time. The electronic nose system consists of two parts: information acquisition the terminal (Acquisition terminal) and information processing terminal (processing terminal). 1) collection terminal is responsible for collecting the signal voltage of the MOS gas sensor array processing terminal via a handheld puter (PDA) to plete the data analysis and processing. Two terminal data exchanged by the two wireless module. Collection terminal consists of three major ponents: sampling systems, electrical systems, as well as the sensor array. The sampling system consists of the the gas sensor cavity, micro plow pump and threeway solenoid valve. Circuit system consists of the following functional modules and power: the microcontroller, ADC module, DAC conditioning modules, memory modules, wireless modules and lithium battery. The sensor cavity is placed with the sensor array consisting of eight mercial TGS gas sensor. The work of energy consumption of the entire collection terminal in 6W about, in the case of the lithium battery with a capacity of 3800Amh powered, it is possible to work continuously . Collection software on the terminal is under in Keil uVision2 development environment with C language, writing good source through the RS232 serial burn to STC89C516KD + microcontroller. 2) processing terminal by a wireless module, microcontroller, RS232 serial port to USB interface module (RS232 to USB), and PDA. Wireless module with microcontroller interface design circuit with the collection terminal. Because on PDA USB interface, it is necessary to design RS232 serial to USB interface circuit to plete the exchange of data between the MCU and PDAs. The electronic nose system software is divided into two parts. The software is based on processing terminal LabVIEW71 (NationalInstrumentation, USA) platform developed on a PDA (WindowsXP system). Electronic nose in a plete test process, have to go through four stages。 ground state phase sampling stage, holding phase and the recovery phase. Stage in the 無(wú)錫科技職業(yè)學(xué)院科技 論文 The application of electronic nose 5 base state, the threeway solenoid valve is switched to the air passage, and a voltage signal of the sensor array to a horizontal baseline. To be a threeway solenoid valve is switched to the sample gas channel into the sampling stage, the sensor array response, a few seconds after the voltage signal value rose to a peak and then stabilized, to be close to equilibrium, the system enters the holding phase, threeway solenoid valve remains constant sample gas channel. The last to enter the recovery phase, threeway solenoid valve is switched back to the air channel, rapid decline in the response curve of the sensor array, until it is restored to the baseline position. The time value of the four stages of the testing process before the start of the test, you must first set on a PDA: the ground state time, sampling time, hold time and recovery time. Then Start mand, the system began to test issued by the PDA. Collection terminal after receiving the order, the internal microcontroller in accordance with the instructions, timer to control the time of the four stages. First, the microcontroller will control the heating voltage of DAC conditioning module output is used to heat the sensor array, and then control the signal voltage of the ADC module acquisition sensor array and choose to get the data saved to the memory module, or directly to the receiver by the wireless module feedback PDA to do the analysis and processing. After the data acquisition is pleted, PDA sends end mand, the system stops working. During the next round of testing is required before the PDA issue a reset mand to make the system cleared before a new round of tests. In addition, in the process of testing, you can issue mands through the PDA miniature air pump and threeway electronic valve control switch. After the test is stopped, the data of the sensor arra y can be read through the open instruction to obtain before and response curves. Statistical methods: Principal ponent analysis (PCA) Principal ponent analysis refers to several variables by linear transformation to elect a fewer number of important variables of multivariate statistical analysis method, also known as principal ponent analysis。 It is a statistical analysis method to grasp the principal contradictio