Automotive Exhaust Gas Sensor Based on an Electrochemical Cell Combined with a Resistive Gas Sensor

Future on-board diagnosis of automotive exhaust gas after-treatment systems might require sensors determining directly the concentration of limited components like hydrocarbons. Suitable sensors for their detection are resistive metal oxide sensors manufactured in film techniques. Besides their sensitivity towards hydrocarbons their signal depends also on the oxygen partial pressure. As the latter varies in the exhaust, it is suggested to integrate the sensor in an ion conducting oxygen pumping cell to establish a constant oxygen concentration at the sensor film. The setup of this sensor system is designed in ceramic tape technology. Since the resistive metal oxide material e.g., gallium oxide and strontium titanate cannot be co-fired with zirconia, a new combination of different materials leading to a three dimensional setup is investigated. This requires new ways of materials joining. In order to show that a constant oxygen concentration can be achieved under lean and under rich exhaust conditions, a resistive oxygen sensor is integrated, proving that the novel concept works properly.