毕业论文-于基单片机的电子换号牌的设计.doc

Nature kind of odor tens of thousands, even professionals specializing in odor

identification work is often recognition errors.

Keywords: electronic nose computer technology developed olfactory organs

physiological reaction "Customs" security monitoring neural networks odor sensor

identification infrared sensor

Introduction: The electronic nose developed a high-tech products is simulated animal

olfactory organ, scientists are still not all clear principle of the animal's sense of smell.

However, with the development of science and technology, more authoritative some

mechanism of the electronic nose is that each sensor in the array has a different

sensitivity of the measured gas. The core of the device of the electronic nose gas

sensor. Gas sensors based on the principle of different type of metal oxide,

electrochemical, and conductive polymer type, quality, photo-ionization type can be

divided into many types. Currently the most widely used is a metal oxide.

How it works:

Electronic nose is mainly composed of three parts of a gas sensor array, signal

pre-processing and pattern recognition. Presented in front of an active material of the

sensor, an odor sensor chemical input is converted into an electrical signal by a

plurality of sensor response to an odor they constitute the sensor array to the odor of

spectrum, according to its characteristic response spectrum can distinguish between

small same odor. While gas sensors constituting the array to measure the

cross-sensitivity of a variety of gases, by a suitable analytical method, the mixed gas

analysis. The electronic nose is the use of various gas sensing device has a response to

this characteristic but different from each other, with the data processing methods to

identify a variety of odor, odor quality analysis and evaluation of complex component

gases. The main mechanism of the electronic nose identify each sensor in the array

has a different sensitivity of the measured gas, e.g., high response One gas may be

generated on a sensor, while the other sensor is a low response; Similarly, the 2nd gas

generating high response of the sensor is not sensitive on the 1st gas and, ultimately,

olfactory receptor cells, neural network and the computer to recognize the biological

equivalent of the brain, the rest is the equivalent of the olfactory nerve signal

transduction system. For example, the measurement of the metal oxide semiconductor

(MOS) gas sensor in response to the schematic diagram of the voltage signal. MOS

work properly. After the chemical reaction occurs in the testing process, the MOS gas

sensor and the sample gas / odor, will change its own gas sensitive film conductivity

and resistance values, leading to a terminal voltage of a sampling resistor in series

thereto is changed. Due to sampling resistor is fixed, so the immediate extraction of

the end of the sampling resistor voltage signal voltage MOS gas sensor response curve.

repeatability; can detect some of the human nose can not detect the gas, such as

specificity greatly enhance the development of sensor materials also contributed to the

improvement of its repetitive, and with the improvement of biochips, biotechnology

development and integration technology, and some nanomaterials The application of

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 compounds (VOC)

and the sensor (ultrasonic sensor), to produce the transient response. Such a response

and the reference gas role of the sensor array used in the initialization process time is

called the "recovery time".

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 computer (PDA) to

wireless module. Collection terminal consists of three major components: sampling

systems, electrical systems, as well as the sensor array. The sampling system consists

of the the gas sensor cavity, micro plow pump and three-way solenoid valve. Circuit

ADC module, DAC conditioning modules, memory modules, wireless modules and

lithium battery. The sensor cavity is placed with the sensor array consisting of eight

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 complete 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).

ground state phase sampling stage, holding phase and the recovery phase. Stage in the