Identification of vapours using a single carbon black/polymer composite sensor and a novel temperature modulation technique

Here we report on a novel method to measure the concentration of different vapours in air using a single carbon black/polymer composite resistive sensor. A carbon black/polyvinylpyrrolidone (PVP) composite film was deposited onto a single crystal silicon micro-hotplate, and its temperature stepped between 25degC and 35 degC. We have extracted a novel pre-processing feature that we describe as the "fractional transient response", which is produced from analyzing the temperature transients measured with and without vapours. We have found that the shape of the fractional difference of transient conductance curve depends only on vapour type and so can be used for vapour identification; whereas the amplitude of fractional difference of transient conductance curves is proportional to the concentration of the vapour and so can be used to predict vapour concentration. Therefore, we show experimentally that it is possible to detect different vapours using a single carbon black polymer/composite sensor. Results are given for detecting water, methanol and ethanol vapours in ambient air.