Tham khảo tài liệu 'wireless sensor networks application centric design part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Odor Recognition and Localization Using Sensor Networks 169 Fig. 2. Basic components of an electronic nose Gardner et al. 1999 Fig. 3. Odor manipulation phases 2. Odor Sensing As mentioned there are many types of odors including the odor in environment pollution. In fact the need for detecting odors that causes pollution and the need for clean environment are leading the research in this field. Reliable real time detection techniques are urgently required especially with the increasing of new diseases that are caused by these odors. Sampling and analytical procedures are no longer on call due to the availability of other techniques that can produce the results on demand. Different sensors have been used to detect odors including Conductivity Piezoelectric Metal-oxide-silicon field-effect-transistor MOSFET Optical Fiber and Spectrometry-Based Sensors. The idea behind the operation of these sensors are explained in Korotkaya 2010 and summarized as follows The conductivity sensors exhibit a change in resistance when exposed to volatile organic compounds. Such sensors respond to water vapor humidity difference but not too sensitive for specific odorants. The Piezoelectric sensors are used to measure temperature mass changes pressure force and acceleration. The main idea behind these sensors is that the gas sample is adsorbed at the surface of the polymer increasing the mass of the disk-polymer device and thereby reducing the resonance frequency. The reduction is inversely proportional to odorant mass adsorbed by the polymer. The MOSFET odor-sensing devices are based on the principle that volatile odor components in contact with a catalytic metal can produce a reaction in the metal. The reaction s products can diffuse through the gate of a MOSFET to change the electrical properties of the device. Optical-fiber sensors utilize glass fibers with a thin chemically active material coating on their slides or ends. A light source at 170 Wireless Sensor Networks .
