Thick-film gas and humidity sensing array based on semiconducting metal oxides

There is considerable interest in the use of sensor array devices (SADs) in instruments both to analyse gas mixtures and to recognise complex odours from foodstuffs and beverages. This paper describes the results of studies on material processing, fabrication and characterisation of a new low-cost, solid state IC 24-pin gas and humidity sensing array based on thick-film technology. The array consists of eight sensing elements on a common substrate and can be used for monitoring the air quality in the gas pipes of civil buildings. A new processing method characterised by using alkali-ions instead of traditional glass frits as adhesion promoter, is applied in mixing the sensor pastes. The sintered sensing layers exhibit a desirable porous structure. The sensors in the array possesses a unique electrode configuration and hence, have a high sensitivity and a fast response. The multiple output signal of the array can be directly used for alarm systems or as input signals for fuzzy logic algorithms for enhancing selectivity of SnO₂ sensors