SENSORS FOR MONITORING ENVIRONMENTAL-POLLUTION

Increasing interest in an unpolluted environment leads to the demand for the reduction of pollutant gases emitted by combustion processes. This requires novel sensor systems which are capable of in situ and real time measurement of the exhaust gas concentrations and thus provide the input signals for an emission-regulated process control. The sensors are manufactured in microsystems technology, using thick-film and thin-film techniques. The operating principles of such sensors are separated in bulk and surface effects. Based on SrTiO3 thin films, oxygen sensors with response times of about 5 ms at operating temperatures of 1000-degrees-C have been implemented (bulk effect). Using these sensors, a cylinder selective lambda measurement in the exhaust gas of an Otto engine is possible, which is fundamental for a novel motor management concept to reduce the emissions. The use of Ga2O3 thin films yields catalytically not active oxygen sensors at high temperatures (bulk effect) and on the other hand sensors for reducing gases (surface effect) at lower temperatures.