Patent ID: 7275415

Claim:
A particulate-based flow system comprising: a flow control mechanism having an input for connection to an engine exhaust system and an output for connection to an engine intake system; a first particulate matter sensor situated at a first location at the input of the flow control mechanism; a second particulate matter sensor situated at a second location at the input of the flow control mechanism; wherein said first and second particulate matter sensors comprise a probe electrode having a passivation layer; a processor connected to the flow control mechanism, the first particulate matter sensor and the second particulate matter sensor; wherein the processor is configured to adjust the flow control mechanism in part according to signals from the first particulate matter sensor and the second particulate matter sensor, wherein the signals from the first and second particulate matter sensors include a rate of flow of particulate matter through the flow control mechanism; wherein the signals from the first particulate matter sensor and the second particulate matter sensor indicate a direction of flow of particulate matter through the flow control mechanism; and wherein when the flow of particulate matter is sensed to be from the input to the output of the flow control mechanism, then the flow control mechanism is configured to allow the flow to continue, and when the flow of particulate matter is sensed to be from the output to the input of the flow control mechanism, then the flow control mechanism is configured to stop the flow.