Electronic Nose Technology Based On The Visual Sense Of Smell And Implementation

E-nose system is a kind of instrument which is composed of selective chemical sensors array and appropriate pattern recognition system to detect and classify simple or complex odorant. With the important applications in the field of food industry, aerospace and environment detection, E-nose system has been studied widely and developed rapidly in the recent years. However, the metal oxide or polymer as vapor-sensing element usually employed in the system has disadvantages of being sensitive to ambient humidity and narrow measuring range which will affect stability, repetition and serviceable range of the sensors.In this paper, an innovative E-nose system has been developed. The principle of odorant recognition is the utilization of color change occuring in an array of metalloporphyrin dyes upon ligand binding when metalloporphyrins are exposed to organic vapors. Unknown smell is recognized by transforming the smell into an image to detect odorants. Furthermore, network can be applied in the "smell-seeing" electronic nose to achieve in-situ detection with the advantages of high detection precision, immunity to environment vapor and monitoring odorants remotely.The technique is based on color change that occurs in an array of vapor-sensitive dyes known as metalloporphyrins - doughnut shaped molecules that bind metal atoms. Simply recording images of arrays "before" and "after" exposed to analytes respectively, it is easy to obtain unique color-change signature for each analyte. Every color-change pattern is so different but unique to the odorants that is like fingerprint of human. Since it can detect odorant with high detecting precision regardless of ambient humidity, "smell-seeing" sensors can meliorate some disadvantages of previous E-nose systems.In the E-nose system, sensitive film of the smell-seeing sensors are factured by four kinds of metalloporphyrins which are Zn(TPP), Co(TPP)(Cl), Fe(TFPP)(Cl) and H2(TPP). The manufacture process of vapor-sensing film is introduced. The design process of the system is described. The satisfying images are obtained by the experimental equipment. The stability of response images obtained under the condition of 95% vapor content compared with those under normal temperature and humidity,validates the conclusion that sensor response cannot be affected by ambient humidity by using image matching algorithm. Additionally, reversible experiment of reactive of sensitive film and odorants has also been done. The experiment results show that the smell-seeing nose can detect odorants regardless of ambient humidity and the sensor film can be used over 100 times.The response signal of sensors is analyzed and processed. Advanced multi-sensor information fusion technique is applied in the recognition algorithm. BP algorithm based on neural network and "euclidean distance " criterion are adopted to recognise the images. Seven analytes are detected successfully by the two algorithms for five times and recognition ratio reached 100%.To extend the application of the "smell-seeing" sensor, an embedded E-nose system is presented in this paper. The SOCKET technology is used to transmit the image information. "Smell-seeing" sensors capture character information of analyte, then the output images are recorded by digital camera. By communicating, processing and recognising images in the embedded system, the long-distance detection of the dangerous environment is realized in-situ.