Assessment of performance in the laboratory

The sensors elaborated with tin dioxide show sensitivity towards the action of maity gases. In general, these sensitivities depend on the nature of the gas and the temperatiue of the sensor. These performances can evolve dming the functioning of the device (ageing effect). 

Figiues 9.18 and 9.19 illustrate such behavior perfectly. We deal here with a sensor elaborated with a serigraphed thick film. It possesses two gold electrodes, obtained by cathodic pulverization. 

These results were obtained continuously through a temperature cycle, and under a gas flow of 5 1/hr. The temperature cycle consists of stabihzing the sensor at 500°C, then decreasing (about a 100°C less per minute) its temperature until it reaches the ambient temperature. 

Nevertheless the maximum conductances are shifted at higher temperatures thus, for alcohol, the maximum which appears at 250°C will be located at 400°C after ageing. 

These results are obtained at 500°C in an aigon/oxygen (5%) mixture and over long periods of time (25 hours in humid air and 90 hours in dry air). 

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