Patent attributes
A smoke sensing device for internal combustion engines comprises an electrode assembly with a heated insulator, a high voltage spark system, a voltage attenuator and a signal conditioning system. The electrode assembly is installed in an engine exhaust pipe so that the spark gap between the electrodes is exposed to the exhaust gas. A series of sparks is produced across the spark gap and the spark voltage is sensed and attenuated to produce a voltage signal. At a selected time during the spark, the voltage signal is compared with a reference voltage. The smoke content of the exhaust gas is derived from the frequency of occurrence of sparks where the voltage signal value is less than the reference value at the selected time. The heated insulator burns off carbon deposits on the insulator surface. The repetitive sparks keep the electrode surfaces free of carbon deposit build-up.
