SENSORS FOR MONITORING ENVIRONMENTAL-POLLUTION

Increasing interest in an unpolluted environment leads to the demand f or the reduction of pollutant gases emitted by combustion processes. T his requires novel sensor systems which are capable of in situ and rea l time measurement of the exhaust gas concentrations and thus provide the input signals for an emission-regulated process control. The senso rs are manufactured in microsystems technology, using thick-film and t hin-film techniques. The operating principles of such sensors are sepa rated 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 senso rs, a cylinder selective lambda measurement in the exhaust gas of an O tto engine is possible, which is fundamental for a novel motor managem ent concept to reduce the emissions. The use of Ga2O3 thin films yield s catalytically not active oxygen sensors at high temperatures (bulk e ffect) and on the other hand sensors for reducing gases (surface effec t) at lower temperatures.