Abstract: A method for spectroscopically detecting a chemical in a gas sample includes illuminating the gas sample with ultraviolet light and photolyzing a first chemical in the gas sample to generate a photolyzed gas sample and spectroscopically detecting a second chemical in the photolyzed gas sample. The second chemical has an optical absorption range within a respective optical absorption range of the first chemical.

Abstract: An automotive exhaust gas sensor includes a gas chamber, an ultraviolet light source configured to emit ultraviolet light into the gas chamber and to photolyze an exhaust gas sample in the gas chamber, and an electrochemical detector disposed in the gas chamber and configured to detect a specified chemical in the photolyzed exhaust gas sample.

Abstract: A method for spectroscopically detecting a chemical in a gas sample includes illuminating the gas sample with ultraviolet light and photolyzing a first chemical in the gas sample to generate a photolyzed gas sample and spectroscopically detecting a second chemical in the photolyzed gas sample. The second chemical has an optical absorption range within a respective optical absorption range of the first chemical.

Abstract: Methods and systems are provided for a particulate matter sensor. In one example, the particulate matter sensor may include a light source, a waveguide aligned with the light source to receive incident light from the light source, and a photodetector positioned to receive light the incident light from the waveguide. The incident light may be reflected off a reflective surface of the waveguide more than one time to generate a plurality of evanescent waves. The plurality of evanescent waves may interact with particulate matter in exhaust gas, causing the incident light to be attenuated.

Abstract: Methods and systems are provided for an oxygen sensor heater. In one example, a method may include applying a less than maximum duty cycle of voltage to the oxygen sensor heater during an engine cold start (e.g., when a temperature of the oxygen sensor is less than its light-off temperature) and adjusting the applied duty cycle of voltage to maintain a constant amount of power. In this way, the oxygen sensor may be heated at a constant rate even as a resistance of the oxygen sensor heater increases, decreasing an amount of time before the oxygen sensor reaches its light-off temperature.

Abstract: Particulate matter (PM) sensors and diagnostics performed using the PM sensors are disclosed. The PM sensors and diagnostics may be used in exhaust systems, such as vehicle exhaust systems, to detect soot. In at least one embodiment, an electrostatic particulate matter (PM) sensor is provided including first and second spaced apart electrodes forming a bulk gap therebetween having a bulk distance and a localized gap therebetween having a localized distance less than the bulk distance. A controller may be configured to control a voltage between the electrodes to induce an electrostatic discharge at the localized gap at a lower voltage than at the bulk gap. Various diagnostics may be performed using the disclosed PM sensors, including a wiring/continuity diagnostic, a soot detection plausibility diagnostic, and/or an installation diagnostic.

Abstract: Methods and systems are provided for an oxygen sensor heater. In one example, a method may include applying a less than maximum duty cycle of voltage to the oxygen sensor heater during an engine cold start (e.g., when a temperature of the oxygen sensor is less than its light-off temperature) and adjusting the applied duty cycle of voltage to maintain a constant amount of power. In this way, the oxygen sensor may be heated at a constant rate even as a resistance of the oxygen sensor heater increases, decreasing an amount of time before the oxygen sensor reaches its light-off temperature.

Abstract: Methods and systems are provided for sensing particulate matter by a particulate matter sensor positioned downstream of a diesel particulate filter in an exhaust system. In one example, a method may include accumulating incoming particulate matter by applying a higher bias to a first trap of the particulate matter sensor, and further charging the particulate matter and forming highly charged dendrites. The method further includes capturing the dendrites exiting the first trap by applying a lower bias to a second trap also housed within the same particulate matter sensor, thereby reducing the effects of exhaust flow rate on the particulate matter sensor and further increasing the sensitivity of the particulate matter sensor.

Abstract: Particulate matter (PM) sensors and diagnostics performed using the PM sensors are disclosed. The PM sensors and diagnostics may be used in exhaust systems, such as vehicle exhaust systems, to detect soot. In at least one embodiment, an electrostatic particulate matter (PM) sensor is provided including first and second spaced apart electrodes forming a bulk gap therebetween having a bulk distance and a localized gap therebetween having a localized distance less than the bulk distance. A controller may be configured to control a voltage between the electrodes to induce an electrostatic discharge at the localized gap at a lower voltage than at the bulk gap. Various diagnostics may be performed using the disclosed PM sensors, including a wiring/continuity diagnostic, a soot detection plausibility diagnostic, and/or an installation diagnostic.

Abstract: Methods and systems are provided for sensing particulate matter by a particulate matter sensor positioned downstream of a diesel particulate filter in an exhaust system. In one example, a method may include accumulating incoming particulate matter by applying a higher bias to a first trap of the particulate matter sensor, and further charging the particulate matter and forming highly charged dendrites. The method further includes capturing the dendrites exiting the first trap by applying a lower bias to a second trap also housed within the same particulate matter sensor, thereby reducing the effects of exhaust flow rate on the particulate matter sensor and further increasing the sensitivity of the particulate matter sensor.