Sensor Used in E-nose - The Electronic Nose Artificial Olfaction Technology - page 157

Fig. 6.11 a Representation of gas sensor, b structure of chemoresistive gas sensor system

and increases electrical resistance of sensor. Electron trapping is decreased by
interface of gases with the surface adsorbed oxygen, leading to increases in
electrical conductance of the sensor. Consecutively to reduce response and
recovery times, metal-oxide sensors are typically run at elevated temperatures (up
to 400 C).
Devices that translate the changes in the concentration of gaseous chemical type
into electrical signals are distinct as metal oxide sensors. MOS sensor basic
schematics as shown in Fig. 6.12 consist a sensitive layer, an insulating layer, two
electrodes, and a heating layer. At temperature level of 250-450 C, the semi-
conducting layer oxidizes the sample compound. Therefore, the semiconducting

Fig. 6.12 Basic metal oxide

sensor