Transient Operation Techniques for Gas Sensor Applications

AbstractThis paper provides an update, how transient operation methods can improve the performance of gas sensors and sensor systems for specific applications. Even new applications can be enabled, if existing state-of-the-art sensors are operated in transient modes adapted to the needs of the application in mind. Several parameters are available for transient variation, depending on the particular sensing technology: Suspended Gate FET sensors deliver a simultaneous readout of work function and capacitive effects. By applying pulsed gate voltages these effects can be interpreted separately and used e.g. for compensation of humidity effects and improved selectivity. Modulation of the operating temperature of μ-machined metal oxide sensors is creating a type of virtual sensor array. In this case, the dynamic behavior of adsorption and desorption at changing temperature levels delivers a fingerprint for application relevant gas mixtures. The pulsed application of charge voltage on standard exhaust lambda probes and the recording of the related discharge characteristic over time provide an exhaust NOx sensor based on a standard sensor setup. The charging creates a misbalance in oxygen-related surface species not available under continuous operation conditions. The related discharge characteristic is strongly influenced by the interaction of these oxygen species with NOx