Gas sensor development for portable monitoring

The use of multi-sensing portable analysers is of increasing importance for many applications. This thesis reports on the development of new portable battery-powered gas analysers suitable for remote site monitoring that can utilise a range of Taguchi tin-oxide sensors as detectors. Two main designs were developed and evaluated for a variety of applications employing head-space analysis. A portable analyser employing the TGS812 and TGS824 Taguchi gas sensors was built in flow-through arrangements. The performance of the gas analyser was evaluated in terms of reproducibility, stability and sensitivity and was used to determine the ethanol content in various commercial beer and wine samples. The adsorption response mechanism of the tin-oxide gas sensors was also investigated using the Langmuir adsorption isotherm model and this model was validated by determining the ethanol content of beer and wine samples. A portable, battery-powered, multi-sensor gas analyser, containing six different Taguchi tin-oxide semiconductors was developed and evaluated. The performance of the portable, battery-powered, multi-sensor gas analyser was evaluated in terms of stability, sensitivity, selectivity and reproducibility. The portable multi-sensor gas analyser was used to determine the ethanol content in various beer samples employing the Langmuir isotherm mentioned above. The portable battery-powered multi-sensor gas analyser mentioned above was used together with back-propagation artificial neural networks and applied to discriminate between beer brands, grades of olive oils, as well as the estimation of the age of olive oil samples.