Abstract: A method for determining the temperature of a sensor that comprises a heater is provided. The method includes the steps of applying a voltage to the heater and measuring the voltage applied to the heater and the current through the heater during a first time interval, and removing the applied voltage from the heater and leaving the heater unpowered for a second time interval. The method further includes the steps of calculating the resistance of the heater using the measured voltage and current, and determining the temperature of the sensor from the resistance using a predetermined relationship. The first time interval is selected to be sufficiently short in duration and the second time interval is selected to be sufficiently long so as to not significantly raise the temperature of the heater. The sensor temperature so determined can be used to perform diagnostic functions for a system that includes the sensor.

Abstract: A method for verifying the validity of an output of a particulate matter sensor mounted in an engine exhaust system downstream of a diesel particulate filter, the particulate matter sensor including a pair of electrodes spaced apart from each other, includes initiating regeneration of the diesel particulate filter, applying and maintaining a higher than nominal voltage across the electrodes following the step of initiating regeneration of the diesel particulate filter, and measuring an electrical parameter across the electrodes while the higher voltage is applied across the electrodes, where the electrical parameter is indicative of an amount of soot accumulated on the sensor. The reading of accumulated soot is evaluated to determine whether the sensor is indicating that the amount of accumulated soot is within an expected range based on a clean diesel particulate filter and the elevated applied voltage.

Abstract: A method for verifying the validity of an output of a particulate matter sensor mounted in an engine exhaust system downstream of a diesel particulate filter, the particulate matter sensor including a pair of electrodes spaced apart from each other, includes initiating regeneration of the diesel particulate filter, applying and maintaining a higher than nominal voltage across the electrodes following the step of initiating regeneration of the diesel particulate filter, and measuring an electrical parameter across the electrodes while the higher voltage is applied across the electrodes, where the electrical parameter is indicative of an amount of soot accumulated on the sensor. The reading of accumulated soot is evaluated to determine whether the sensor is indicating that the amount of accumulated soot is within an expected range based on a clean diesel particulate filter and the elevated applied voltage.

Abstract: A particulate sensing system configured to detect particulates in exhaust gas from a combustion process. Particulates are detected based on electrical conductivity between a first electrode and a second electrode. A heater element is provided to heat the first electrode and the second electrode. The first electrode, the second electrode, and the heater element cooperate to form a sensor. The heater element is operated to establish a sensor temperature greater than a dew-point temperature of the exhaust gas and less than a burn-off temperature of the sensor to reduce thermophoretic accumulation of particulates on the sensor. When the exhaust temperature and the sensor temperature are suitable for thermophoretic accumulation and electrophoretic accumulation of particulates, a voltage is applied across the electrodes to facilitate electrophoretic accumulation of particulates, and the heater element is turned off so thermophoretic accumulation occurs.

Abstract: A particulate matter sensor includes first and second electrodes spaced from each other with a bias resistor connected between the first and second electrodes. The particulate matter sensor allows an open circuit fault condition in the sensor or in the connectors or wiring to the sensor to be detected. A sensing system using the particulate matter sensor and a method for diagnosing faults in a sensing system are also provided.

Abstract: A particulate matter sensor includes a first pair of sensing electrodes with a gap therebetween and a second pair of sensing electrodes with a gap therebetween. A method for determining an amount of soot on the particulate matter sensor includes determining the electrical resistance between the first pair of electrodes and the electrical resistance between the second pair of electrodes. The amount of soot deposited on the particulate matter sensor is determined based on the electrical resistance values. The time rate of change of resistance between the first pair of electrodes and the time rate of change of resistance between the second pair of electrodes are determined. The first and second rates of change are compared to each other and to threshold values, and the determination of soot amount may be modified depending on the results of these comparisons.

Abstract: A diagnostic method and system is described for diagnosing an operating condition of a conductive particulate matter sensor. The sensor has a substrate with electrical resistance that varies with temperature and two electrodes on the substrate adapted to collect particulate matter between the electrodes, thereby establishing an electrically conductive path through collected particulate matter between the electrodes that can be detected by measuring electrical resistance between the electrodes, Relect. The diagnosis is performed by heating the substrate in the area between the electrodes and using the resistance between the electrodes to determine detecting whether contamination is present on the surface of the sensor. Heat may be maintained on the sensor to attempt to burn off a detected contaminant, and a subsequent resistance reading may be used to determine if the contaminant was successfully burned off.

Abstract: A method of detecting particulate matter on a particulate matter sensor includes the steps of measuring an electrical characteristic associated with the sensor, determining a value corresponding to the impedance across the sensor, and compensating the impedance for the temperature at which it was determined. The method further includes determining an estimate of the total amount of particulate matter accumulated while limiting the effects of large particles captured on the sensor or blown off the sensor. The information produced by the method may be used to provide diagnostic information regarding a particulate control system.

Abstract: A particulate matter sensor includes a first pair of sensing electrodes with a gap therebetween and a second pair of sensing electrodes with a gap therebetween. A method for determining an amount of soot on the particulate matter sensor includes determining the electrical resistance between the first pair of electrodes and the electrical resistance between the second pair of electrodes. The amount of soot deposited on the particulate matter sensor is determined based on the electrical resistance values. The time rate of change of resistance between the first pair of electrodes and the time rate of change of resistance between the second pair of electrodes are determined. The first and second rates of change are compared to each other and to threshold values, and the determination of soot amount may be modified depending on the results of these comparisons.

Abstract: A method for determining the temperature of a sensor that comprises a heater is provided. The method includes the steps of applying a voltage to the heater and measuring the voltage applied to the heater and the current through the heater during a first time interval, and removing the applied voltage from the heater and leaving the heater unpowered for a second time interval. The method further includes the steps of calculating the resistance of the heater using the measured voltage and current, and determining the temperature of the sensor from the resistance using a predetermined relationship. The first time interval is selected to be sufficiently short in duration and the second time interval is selected to be sufficiently long so as to not significantly raise the temperature of the heater. The sensor temperature so determined can be used to perform diagnostic functions for a system that includes the sensor.

Abstract: A diagnostic method and system is described for diagnosing an operating condition of a conductive particulate matter sensor. The sensor has a substrate with electrical resistance that varies with temperature and two electrodes on the substrate adapted to collect particulate matter between the electrodes, thereby establishing an electrically conductive path through collected particulate matter between the electrodes that can be detected by measuring electrical resistance between the electrodes, Relect. The diagnosis is performed by heating the substrate in the area between the electrodes and using the resistance between the electrodes to determine detecting whether contamination is present on the surface of the sensor. Heat may be maintained on the sensor to attempt to burn off a detected contaminant, and a subsequent resistance reading may be used to determine if the contaminant was successfully burned off.

Abstract: A method and system is described for removing contamination from a conductive particulate matter sensor. The sensor has a substrate with two electrodes on the substrate configured to collect particulate matter between the electrodes, thereby establishing an electrically conductive path through collected particulate matter between the electrodes that can be detected by measuring electrical resistance between the electrodes. The method includes heating the sensor to a first temperature for a first duration of time, wherein the first temperature and first time are sufficient to remove collected particulate matter from the sensor. The method further includes heating the sensor to a second temperature for a second duration of time, wherein the second temperature is higher than the first temperature, to remove contaminants that cannot be removed by heating to the first temperature for the first duration of time.

Abstract: A method of detecting particulate matter on a particulate matter sensor includes the steps of measuring an electrical characteristic associated with the sensor, determining a value corresponding to the impedance across the sensor, and compensating the impedance for the temperature at which it was determined. The method further includes determining an estimate of the total amount of particulate matter accumulated while limiting the effects of large particles captured on the sensor or blown off the sensor. The information produced by the method may be used to provide diagnostic information regarding a particulate control system.

Abstract: A diagnostic method and system is described for diagnosing an operating condition of a conductive particulate matter sensor. The sensor has a substrate with electrical resistance that varies with temperature and two electrodes on the substrate adapted to collect particulate matter between the electrodes, thereby establishing an electrically conductive path through collected particulate matter between the electrodes that can be detected by measuring electrical resistance between the electrodes, Relect. The diagnosis is performed by heating the substrate in the area between the electrodes and detecting whether resistance varies with temperature as expected, and then cooling the substrate back down and detecting whether resistance varies with temperature as expected. If resistance varies as expected during both heating and cooling, then a validation is diagnosed that the sensor is in proper operating condition if resistance increases in a manner consistent with evaporation of condensate.

Abstract: A diagnostic method and system is described for diagnosing an operating condition of a conductive particulate matter sensor. The sensor has a substrate and two electrodes on the substrate adapted to collect particulate matter between the electrodes, thereby establishing an electrically conductive path through collected particulate matter between the electrodes that can be detected by measuring electrical resistance between the electrodes, Relect. The diagnosis is performed by detecting whether water vapor condensate may be present between the electrodes and if it is, then measuring resistance between the electrodes while subjecting the sensor to conditions sufficient to evaporate any water vapor condensate and diagnosing a validation that the sensor is in proper operating condition if resistance increases in a manner consistent with evaporation of condensate.

Abstract: A particulate matter sensor includes first and second electrodes spaced from each other with a bias resistor connected between the first and second electrodes. The particulate matter sensor allows an open circuit fault condition in the sensor or in the connectors or wiring to the sensor to be detected. A sensing system using the particulate matter sensor and a method for diagnosing faults in a sensing system are also provided.

Abstract: A diagnostic method and system is described for diagnosing an operating condition of a conductive particulate matter sensor. The sensor has a substrate and two electrodes on the substrate adapted to collect particulate matter between the electrodes, thereby establishing an electrically conductive path through collected particulate matter between the electrodes that can be detected by measuring electrical resistance between the electrodes, Relect. The diagnosis is performed by detecting whether water vapor condensate may be present between the electrodes and if it is, then measuring resistance between the electrodes while subjecting the sensor to conditions sufficient to evaporate any water vapor condensate and diagnosing a validation that the sensor is in proper operating condition if resistance increases in a manner consistent with evaporation of condensate.

Abstract: A diagnostic method and system is described for diagnosing an operating condition of a conductive particulate matter sensor. The sensor has a substrate with electrical resistance that varies with temperature and two electrodes on the substrate adapted to collect particulate matter between the electrodes, thereby establishing an electrically conductive path through collected particulate matter between the electrodes that can be detected by measuring electrical resistance between the electrodes, Relect. The diagnosis is performed by heating the substrate in the area between the electrodes and detecting whether resistance varies with temperature as expected, and then cooling the substrate back down and detecting whether resistance varies with temperature as expected. If resistance varies as expected during both heating and cooling, then a validation is diagnosed that the sensor is in proper operating condition if resistance increases in a manner consistent with evaporation of condensate.

Abstract: The phase winding energization frequency of a stepper motor throttle operator is adjusted in relation to a comparison between the actual neutral voltage crossing of back-EMF in the phase windings and a previously determined optimum point of crossing. The energization frequency is increased to increase motor speed when the actual crossing occurs prior to the optimum point, and decreased to decrease motor speed when the actual crossing occurs after the optimum point.