Conductance-transient analysis of thick-film tin oxide gas sensors under successive gas-injection steps

Dynamically characterizing the electrical response of chemical sensors is a strategy to improve their selectivity. In this paper, the conductance transient of thick-film tin oxide gas sensors under successive step rises in the gas concentration is analysed. The transient response of three thick-film tin oxide gas sensors in the presence of organic solvent vapours (toluene, o-xylene and ethanol) has been measured. As a main result, it has been found that, although the first step in the conductance-transient rise time is concentration independent, for the second and successive steps, decreases and becomes concentration dependent. This behaviour has been modelled successfully with a nonlinear diffusion - reaction model. The measured set of rise times is characteristic for each sensor - gas pair and may give useful information for gas recognition. Furthermore, the successive injection of gas samples during the sensor-calibration procedure may be a time-saving technique.