Multigas sensor based on micro machined hotplates for CO and O2 detection using catalytically modified nano-SnO2

SnO₂ nanostructures have been loaded with different amount and types of catalysts. These ones work as active filters that functionally response in a very different way against carbon monoxide and oxygen. The micro machined hotplates contain different thermally and electrically independent membranes integrated in the same chip allowing that one of the active sensing materials is turned to present a higher sensitivity to CO than to O2, whereas the other sensor is mainly turned for detecting O2 variations without any cross talk of temperature. The resistance data obtained from this type of combined sensors as a function of CO and O₂ concentrations has been parameterized and modulated for the direct deduction of the both gas concentrations. So, two functions are calculated for the quantification of CO/O₂ gas mixtures. A comparison with a reference oxygen sensor based on a perovskite type barium stannate layer of BaSnO₃ working as oxygen gas sensor at high temperature and not presenting interfering crosstalk with the CO concentration is also discussed.