ABSTRACT
Ceramic gas sensors can be classified according to different principles such as: the chemical properties of the gas, the sensitivity region of the ceramics, the conductivity mechanism, the measured physical quantity, and the field of application. According to the field of application the ceramic gas sensors can be classified into: reducing gas sensors, toxic gas sensors, alcohol sensors, odor sensors, oxygen sensors, and other gas sensors. The operating temperature should be specified for any sensor. It is a function of the ceramic composition and of the gas which is to be detected. The selectivity of a sensor in relation to a definite gas is closely connected with its operating temperature. The operating temperature control is a means of regulating the sensor selectivity, whereupon a single sensor can be used to detect various gases. The thermal cycling of the sensor elements is a promising method for improving the selectivity of the ceramic gas sensors.
