ANALYSIS OF THE CONDUCTANCE TRANSIENT IN THICK-FILM TIN OXIDE GAS SENSORS

In this paper, we analyse the conductance transient of a Taguchi TGS-8 22 sensor under a step change in the vapour concentration. A diffusion -limited range in the conductance transient is observed. Adjustments b etween the theoretical calculations based on a non-linear diffusion-re action model and the experimental results allow a constant, tau', to b e estimated, which is independent of the final conductance value and d epends, among other parameters, on the effective diffusion coefficient of vapours in the porous tin oxide sensor. From transient measurement s of organic solvents (benzene and o-xylene) we have obtained tau' val ues that are independent of concentration and characteristic for each vapour. This new parameter can give useful information for gas/vapour recognition.