Particulate Matter Sensor for On Board Diagnostics (OBD) of Diesel Particulate Filters (DPF)

The emissions legislation in the US and Europe introduce the need for the application of diesel particulate filters (DPF) in most Diesel vehicles. In order to fulfill future OBD legislations, which include more stringent requirements on monitoring the functionality of those particulate filters, new sensors besides the differential pressure sensor are necessary. The new sensors need to directly detect the soot emission after DPF and withstand the harsh exhaust gas environment. Based on multi layer ceramic sensor technology an exhaust gas sensor for particulate matter (EGS-PM) has been developed. The soot particle sensing element consists of two inter-digitated comb-like electrodes with an initially infinite electrical resistance. During the sensor operation soot particles from the exhaust gas are collected onto the interdigital electrodes and form conductive paths between the two electrode fingers leading to a drop of the electrical resistance. A controlled regeneration of the soot detecting electrodes is conducted by heating the sensing element and burning off the deposited soot at temperatures above 600°C. The concept and the performance of the EGS-PM as well as a new concept for the OBD of diesel particulate filters using the EGS-PM are presented.