CONDUCTANCE-TRANSIENT ANALYSIS OF THICK-FLINT 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 conduc tance transient of thick-film tin oxide gas sensors under successive s tep 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 (T-r) is concentration independent, fo r the second and successive steps, T-r decreases and becomes concentra tion dependent. This behaviour has been modelled successfully with a n onlinear diffusion-reaction model. The measured set of rise times is c haracteristic for each sensor-gas pair and may give useful information for gas recognition. Furthermore, the successive injection of gas sam ples during the sensor-calibration procedure may be a time-saving tech nique.