Particle detectors and methods for detecting particulate matter accumulated on a surface are provided. According to one aspect, the particle detector may comprise a substrate, an optical light source configured to emit light along a light path, a waveguide associated with the substrate, having a surface exposed to a gaseous environment and configured to accumulate on the surface particulate matter from the gaseous environment, a detector configured to receive the emitted light from the waveguide, and a controller configured to determine the intensity of the detected light and output an indication of an opacity of the surface of the waveguide with the accumulated particulate matter.

Particle measurement apparatus comprises an inlet for receiving a gas sample for analysis, a photoionisation chamber, at least one light source arranged to illuminate an interior of the photoionisation chamber, first and second electrodes coupled to a power source and configured to provide a DC potential difference across at least a portion of the photoionisation chamber, and an outlet, together defining a gas flow path from the inlet, through the photoionisation chamber, and towards the outlet.

In a particulate detection system (10), a control board (911), a high voltage generation board (913) and an isolation transformer (720) are respectively disposed in a first space (921d) and a second space (921e) separated from each other by an inner case (923). When electromagnetic noise is generated in the high voltage generation board (913) and the isolation transformer (720); specifically, at the primary winding of the isolation transformer 720, at the time of switching the primary current supply, the electromagnetic noise is blocked by the inner case (923). This configuration reduces the influence of electromagnetic noise generated in the primary winding on the control board (911).

Methods and systems are provided for a particulate matter sensor. In one example, the sensor may include a concave inlet for admitting exhaust gas from an exhaust passage downstream of a particulate filter into the sensor.

A particulate matter detection sensor has an accumulation section for accumulating a part of particulate matter particles contained in exhaust gas emitted from an internal combustion engine, and a pair of a first detection electrode and a second detection electrode formed on the accumulation section. The second detection electrode is formed separated from the first detection electrode. The first detection electrode has projecting parts which project toward the second detection electrode. Because a separation between the first and second detection electrodes is locally reduced at the projecting parts, the projecting parts attract and accumulate more particulate matter, and this structure makes it possible to allow the particulate matter detection sensor to have improved detection sensitivity.

Methods and systems are provided for reducing soot sensor electrode degradation in harsh chemical environment introduced as a result of desulfation of a lean NOx trap positioned upstream of the soot sensor. In one example, a method may include in response to the SOx load being higher than the threshold, prior to initiating desulfation of LNT, operating the soot sensor in a pre-desulfation mode where the negative electrode is connected to the positive electrode for a brief duration, while the positive electrode is disconnected from the positive electrode. However during desulfation, when H.sub.2S is released as a by-product, both the electrodes may be open, i.e. not connected to the positive electrode or ground, thereby reducing the possibility of sensor degradation.

A control unit (6) estimates an output value of a PM sensor (S2) located at a downstream side of a DPF used as a reference filter, and detects whether the estimated output value exceeds a predetermined value (S3). When the estimated output value exceeds the predetermined value (YES in S3), the control unit detects an output value of the PM sensor (S4), and a heater heats the PM sensor (S5). The control unit detects an output value of the PM sensor (S6) after the PM sensor is heated, and calculates a change ratio of the output values of the PM sensor before and after heating (S7). The control unit estimates an average particle size of PM based on the calculated change ratio (S8), and detects whether the DPF has failed based on a comparison result of a corrected output value of the PM sensor with a threshold value.

A method is provided for controlling the function of a sensor for detecting particles, in particular soot particles, the sensor including at least two measuring electrodes and a substrate on which the measuring electrodes are situated. The method includes the following: carrying out a first current-voltage measurement for ascertaining a first measured variable; carrying out a second current-voltage measurement for ascertaining a second measured variable, one measuring electrode of the measuring electrodes being applied to another electrical potential; carrying out a third current-voltage measurement for ascertaining a third measured variable; an configured forming a correction value for correcting the second measured variable with the aid of the first measured variable and the third measured variable.

A particulate matter sensor unit is configured to sense particulate matter included in exhaust gas of a vehicle. The particulate matter sensor unit includes: a sensing unit sensing the particulate matter in the exhaust gas; a holding unit including a plurality of holders covering an exterior of the sensing unit, a front outer surface of each holder being formed by a tapered inclination outer surface; a shell having a hollow portion therein so that the holding unit is inserted and fitted into the shell, an inclination inner surface being formed in the hollow portion to correspond to the inclination outer surface; a cap unit installed in front of the shell to cover a sensing body of the sensing unit and guiding a flow of the exhaust gas to go through the sensing body; and a cover fixed to a rear end of the shell to support the holding unit.

Methods and systems are provided for a particulate matter sensor positioned downstream of a diesel particulate filter in an exhaust system. In one example, a particulate matter sensor may include a spherical assembly including a hollow rod and a plurality of flow tubes connected to diametrically opposite ends of the assembly, and a sensor element positioned within the assembly, distal to the plurality of flow tubes, thus protecting the sensor element from contaminants and water droplets condensing at or near the plurality of flow tubes. In addition, the support rod may further include a drainage hole to flow larger particulates out the spherical assembly and out into the exhaust passage.