Recent Developments in the Field of Automotive Exhaust Gas Ammonia Sensing

Steadily increasing emission standards for both passenger cars and heavy duty vehicles combined with the need for fuel efficiency lead to novel leanly operated powertrain concepts and to novel exhaust gas aftertreatment systems like NOx storage catalysts, ammonia SCR (selective catalytic reduction) NOx reduction catalysts, or even to a combination of both. In order to control these novel systems and to monitor on-board their proper operation (on-board diagnosis, OBD), novel exhaust gas sensors are required or would at least be very helpful. Amongst others, several types of NH3 sensors and of sensors to directly measure the ammonia loading of SCR catalysts are under development or in the research state. This brief overview reviews and evaluates recent developments and adds some results of suggested improvements.