Method and apparatus for operating a collecting particle sensor

Abstract

Method for operating a collecting particle sensor (10) for determining the particle content of an exhaust gas, wherein the particle sensor (10) comprises at least two electrodes (12, 13), wherein during a measurement phase a measuring voltage (51) provided by a voltage source (30) is applied across the electrodes (12, 13) and a subsequent current measuring shunt (46), wherein, to determine the particle content in the exhaust gas, a change in a current (24) between the electrodes (12, 13) due to particles (15) deposited on the particle sensor (10) from the exhaust gas is evaluated, and wherein a measurable current is limited by a maximum current (21), characterized in that, upon reaching the maximum current (21), the measuring voltage (51) is determined, and that a control unit detects a short circuit between the electrodes (12, 13) or the leads to the electrodes (12, 13).if the measuring voltage (51) is below a predetermined first voltage threshold (52) and a high particle loading of the particle sensor (10) is inferred if the measuring voltage (51) is above a predetermined second voltage threshold (52), wherein to determine the current (24) between the electrodes (12, 13) a voltage drop across the current measuring shunt (46) connected in series with the electrodes (12, 13) is determined and that to determine the measuring voltage (51) a voltage drop across a resistor (42) of a voltage divider (40) connected in parallel to the electrodes (12, 13) and the current measuring shunt (46) is determined, wherein the measurable current is limited by the maximum current (21) by a first evaluation circuit determining the voltage drop across the current measuring shunt (46) and thus determining the current (24) through the electrodes (12, 13), wherein the maximum current (21) is limited by the measuring range of the first evaluation circuit is specifiedwherein, to determine the measured voltage (51), a second evaluation circuit for voltage measurement is connected in parallel to the resistor (42) of the voltage divider (40).

Description

State of the art

[0001] The invention relates to a method for operating a collecting particle sensor for determining the particle content of an exhaust gas, wherein the particle sensor contains at least two electrodes, wherein during a measuring phase a measuring voltage provided by a voltage source is applied across the electrodes and a subsequent current measuring shunt, wherein to determine the particle content in the exhaust gas a change in a current between the electrodes by particles from the exhaust gas deposited on the particle sensor is evaluated and wherein the measurable current is limited by a maximum current.

[0002] The invention further relates to a device for operating a collecting particle sensor for determining the particle content of an exhaust gas, wherein the particle sensor contains at least two electrodes to which particles from the exhaust gas accumulate and the electrodes are electrically connected, with a voltage source for applying a measuring voltage across the electrodes and a current measuring shunt connected in series with the electrodes, with a first evaluation circuit for determining a voltage drop across the current measuring shunt for determining a current through the electrodes, wherein a maximum measurable current between the electrodes is predetermined by the measuring range of the first evaluation circuit, and with a control unit for determining the particle loading of the particle sensor from the determined current through the electrodes.

[0003] Particle sensors are used today, for example, to monitor soot emissions from internal combustion engines and for on-board diagnostics (OBD), such as monitoring the functionality of particulate filters. Collecting, resistive particle sensors are known for this purpose. These sensors evaluate changes in the electrical properties of an interdigital electrode structure due to particle deposits. When the particle sensor is fully loaded, the deposited particles are burned off in a regeneration phase using a heating element integrated into the particle sensor.

[0004] Such a resistive particle sensor is described in DE 101 33 384 A1. The particle sensor is constructed of two interlocking, comb-like electrodes (interdigital electrodes) that are at least partially covered by a capture sleeve. If particles from a gas stream deposit on the particle sensor, this leads to an analyzable change in the impedance of the particle sensor, from which the quantity of deposited particles and thus the quantity of particles entrained in the exhaust gas can be determined.

[0005] The accumulation of particles on a particle sensor located downstream of a particulate filter in the exhaust stream depends on the filter's efficiency and the particle filter's load. Exhaust gas downstream of an intact particulate filter contains virtually no particles. If the particulate filter is fully loaded or if its filtering efficiency is limited, particles created during combustion can pass through the particulate filter and deposit on the particle sensor, which is detected by evaluating the particle sensor's output signal. This allows the function of the particulate filter to be monitored.

[0006] During the regeneration of the particle sensor, which is necessary when the particle sensor reaches a certain load level, the integrated heating element heats it up to such an extent that the accumulated soot particles burn off.

[0007] To determine the impedance of the particle sensor, the electrodes are typically connected in series to a voltage source via a current measuring shunt. By measuring the voltage drop across the current measuring shunt, which can be done using an analog-to-digital converter, for example, the current flow through the electrodes, which depends on the particle load of the particle sensor, is measured. This allows conclusions to be drawn about the impedance or, directly, the particle load. In the case of very heavy soot deposits on the interdigital electrodes, for example, due to a severely defective particulate filter, the sensor signal rises above the maximum limit of the measurable current range, which can be determined, for example, by the maximum voltage of the analog-to-digital converter. However, this limit can also be exceeded by a short circuit between the electrodes or the supply lines to the electrodes. Therefore, it is not possible to attribute the exceeding of the maximum current limit to a short circuit or a heavy particle load in the particulate sensor.

[0008] Such a distinction can be made possible, for example, by an extended measurable current range, but this can only be implemented at increased costs.

[0009] Another way to distinguish between a short circuit and a high particle load is to perform a new regeneration of the particle sensor when the maximum measurable current is exceeded. Immediately after the end of the regeneration, the only possible cause for a continued current limit being exceeded is a short circuit, since deposited particles are burned off during the regeneration, thus causing the current limit to be undershot, at least briefly.

[0010] The disadvantage here is the high time expenditure, as a full regeneration phase must be completed before a possible fault in the particulate sensor can be detected. Due to this waiting time, according to the current specifications for on-board diagnostics (OBD) in motor vehicles, a good message from a particulate filter to be monitored must be delayed by this time, which adversely increases the OBD-IUMPR (In Use Monitor Performance Ratio). A further disadvantage is that in the case of a very badly damaged particulate filter, so many particles may have accumulated on the particle sensor's electrodes immediately after regeneration that the current measuring range is immediately exceeded again, making it impossible to distinguish between a short circuit and a heavy particle load. It should also be noted that each additional regeneration of the particulate sensor contributes to the aging of the sensor element.

[0011] The document DE 10 2009 033 232 A1 describes a method for the on-board functional diagnosis of a soot sensor and / or for detecting other components in the soot in a motor vehicle with an internal combustion engine. The soot sensor is electrically connected to an evaluation circuit permanently installed in the motor vehicle. The evaluation circuit measures the voltage coefficient of the soot sensor and detects the faultiness of the soot sensor and / or the presence of other components in the soot based on the voltage coefficient. The voltage coefficient represents a dependence of a resistance on an applied voltage. In the case of an intact soot sensor, the voltage coefficient is very high because the resistance value of the intact soot sensor is derived primarily from the high electric field strength between the measuring electrodes. The resistance measured at the soot sensor is influenced by the soot layer on the measuring electrodes of the soot sensor.As a result, the measured resistance is highly dependent on the measurement voltage. A healthy and fault-free soot sensor is characterized by a high voltage coefficient. In the event of a short circuit, the current flows through a metallic connection that has only a small voltage coefficient. By measuring the voltage coefficient, a distinction can be made between a healthy particle sensor and one with a short circuit. The disadvantage, however, is the complex measurement process with a correspondingly costly power supply circuit, since the particle sensor must be subjected to different voltages to determine the voltage coefficient.

[0012] Further particle sensors or devices and methods for their operation are known from DE 10 2010 030 634 A1.

[0013] It is therefore an object of the invention to provide a method which enables a direct distinction between a short circuit and a high particle load of a collecting particle sensor.

[0014] It is a further object of the invention to provide a device for carrying out the method. Disclosure of the invention

[0015] The object of the invention relating to the method is achieved in that the measuring voltage is determined when the maximum current is reached and that a short circuit between the electrodes or the leads to the electrodes is concluded if the measuring voltage is below a predetermined first voltage threshold and that a high particle load of the particle sensor is concluded if the measuring voltage is above a predetermined second voltage threshold. In the event of a short circuit between the electrodes or the leads to the electrodes, the load on the voltage source providing the measuring voltage is greater than the load when the particle sensor is heavily loaded with particles. This leads to a greater voltage drop in the measuring voltage compared to when the particle load is heavily loaded in the event of a short circuit, which is detected according to the invention by comparison with the voltage thresholds.The method thus makes it possible to quickly and reliably distinguish between a heavily particle-laden particle sensor and a short circuit after a possible defect in the particle sensor or a particle filter being monitored by the particle sensor has been indicated by reaching the maximum current. This allows a good signal for the particle filter to be issued earlier, thereby increasing the OBD IUMPR. Unnecessary regenerations of the particle sensor can be avoided. Even with a very high particle content in the exhaust gas, for example, with a severely damaged particle filter, there is no risk of confusion between a short circuit and a heavily particle-laden particle sensor, as is the case, for example, in an evaluation immediately after a particle sensor regeneration.

[0016] By appropriately selecting the first, preferably lower voltage threshold for detecting a short circuit and the second, preferably higher voltage threshold for detecting a heavy particle load, a reliable distinction can be ensured between a short circuit and a heavy particle load. According to a preferred method variant, the implementation of the method can be simplified by making the first voltage threshold the same as the second voltage threshold. For evaluation, it is therefore only necessary to determine whether the measuring voltage is above or below the common voltage threshold after the maximum current has been reached. A short circuit occurs when the measuring voltage is lower than the common voltage threshold, while a measuring voltage higher than the common voltage threshold can be assumed to indicate a heavy particle load and therefore a defective particulate filter.

[0017] A simple and cost-effective determination of both the current between the electrodes and the measuring voltage can be achieved by determining a voltage drop across the current measuring shunt connected in series with the electrodes to determine the current between the electrodes and / or by determining a voltage drop across a resistor of a voltage divider connected in parallel with the electrodes and the current measuring shunt to determine the measuring voltage.

[0018] The method exploits the fact that the measurement voltage drops when the voltage source is loaded by a low-resistance short circuit. For this purpose, a linear voltage source or a non-linear voltage source can be used to provide the measurement voltage. A non-linear voltage source offers the additional advantage that when a defined load is exceeded, the source voltage of the voltage source itself drops, thus resulting in a very strong and reliably detectable drop in the measurement voltage in the event of a short circuit.

[0019] The extent to which the measuring voltage drops depends on the impedance of the voltage source and its load. The load results from the current flow through the electrodes and the downstream current measuring shunt as well as through the voltage divider connected in parallel. In order to enable a reliable distinction between a high particle load in the particle sensor and a short circuit, the internal impedance of the voltage source and / or the total resistance of the voltage divider can be adapted to the impedance curve of the particle sensor in such a way that the measuring voltage drops sharply in the event of a short circuit and only slightly in the event of a high particle load. This ensures that the measuring voltage drops below the first voltage threshold or a common voltage threshold in the event of a short circuit, while it remains above the second voltage threshold or the common voltage threshold in the event of a high particle load.

[0020] The object of the invention relating to the device is achieved in that a voltage divider is connected in parallel to the electrodes and the current measuring shunt, in that a second evaluation circuit for voltage measurement is connected in parallel to a resistor of the voltage divider and is connected to or integrated in the control unit to determine the measuring voltage, in that a program sequence or a circuit arrangement is provided in the control unit for comparing the measuring voltage determined when the maximum current is reached with a predetermined first voltage threshold and a predetermined second voltage threshold, and in that a program sequence is provided in the control unit for detecting a short circuit between the electrodes or the leads to the electrodes when the determined measuring voltage falls below the first voltage threshold or for detecting a heavy particle load of the particle sensor,when the specific measurement voltage exceeds the second voltage threshold. The device thus enables the described method to be carried out.

[0021] A simple design of the device is made possible by the fact that the first evaluation circuit and / or the second evaluation circuit are each formed by an analog-to-digital converter. These enable the conversion of the applied voltage signals into digital signals, which can be easily processed by the downstream control unit. The maximum current is determined by the measuring range of the first evaluation circuit, i.e., the first analog-to-digital converter.

[0022] Simple programming with a reliable distinction between a short circuit and a heavy particle load is achieved by ensuring that the first voltage threshold and the second voltage threshold are the same.

[0023] The invention is explained in more detail below using an exemplary embodiment illustrated in the figures. They show: Fig. 1 schematically shows a particle sensor in an exploded view, Fig. 2 schematically shows a section through the particle sensor with a formed soot path, Fig. 3 a diagram showing the time course of a measured current and an actual current when the particle sensor is heavily loaded with particles, Fig. 4 a diagram showing the time course of a measured current and an actual current in the case of a short circuit between electrodes of the particle sensor, Fig. 5 an electrical circuit for operating a particle sensor, Fig. 6 a double diagram showing the time course of a measured current, an actual current and a measuring voltage under heavy particle loading of the particle sensor, Fig. 7 double diagram showing the time course of a measured current, an actual current and a measuring voltage in the event of a short circuit between electrodes of the particle sensor.

[0024] Fig. 1 shows a schematic representation of a particle sensor 10 in an exploded view.

[0025] A first electrode 12 and a second electrode 13 are applied to insulating carrier layers 11, for example, made of aluminum oxide. The electrodes 12, 13 are designed in the form of two interlocking, interdigital comb electrodes.

[0026] In the example shown, a heating element 14 is integrated between the insulation carrier layers 11.

[0027] If such a particle sensor 10 is operated in a gas stream containing particles, for example in the exhaust duct of a diesel engine, particles 15 from the gas stream will deposit on the particle sensor 10. In the case of a diesel engine, the particles 15 are soot particles with a corresponding electrical conductivity. When the particle sensor 10 is sufficiently loaded, these particles form conductive bridges between the electrodes 12, 13. The deposition rate of the particles 15 on the particle sensor 10 depends on the particle concentration in the exhaust gas. By measuring the temporal course of the current or by measuring the time from the start of a measuring cycle until a current referred to as the trigger threshold is reached between the two electrodes 12, 13 with a constant voltage applied, conclusions can be drawn about the particle deposition and thus about the particle concentration in the exhaust gas.This enables, for example, the monitoring of the function of a particle filter connected upstream of the particle sensor 10 in the exhaust duct.

[0028] After completion of a measurement cycle, the particles 15 deposited on the particle sensor 10 are burned as part of a regeneration of the particle sensor 10. For this purpose, the temperature of the particle sensor 10 is increased to approximately 750°C using the heating element 14.

[0029] Fig. Figure 2 shows a schematic section through the particle sensor 10 with a formed soot path 16. The same identifiers as in Fig. 1 introduced used.

[0030] The conductive particles 15 deposited between the electrodes 12, 13 form conductive soot paths 16 between the electrodes 12, 13, over which an evaluable electric current flows.

[0031] In the event of a very high particle load on the electrodes 12, 13, for example, due to a severely defective particulate filter, the output signal of the particulate sensor 10 rises above the maximum limit of the measurable current range. However, this limit can also be caused by a short circuit between the electrodes 12, 13 or their supply lines. Therefore, it is not possible to directly distinguish between a short circuit, i.e., a defect in the particulate sensor 10, and a very high particle content in the exhaust gas with a correspondingly high particle load on the particulate sensor, as occurs as a result of a severely defective particulate filter. The necessary expansion of the measurable current range is costly and difficult to integrate into existing evaluation systems for particulate sensors.

[0032] Fig. 3 shows a diagram of the time course of a measured current 22 and an actual current 23 with a high particle load as the output signal of the Fig. 1 and Fig. 2 shown particle sensor 10.

[0033] The measured current 22 and the actual current 23 are plotted against a current axis 20 and a time axis 26. A maximum limit of the measurable current range is indicated by a maximum current 21. From the maximum current 21, the measured current 22 deviates from the actual current 24. After a regeneration phase 25 symbolized by a square, the current flow through the electrodes 12, 13 falls back into the measurable range, so that the measured current 22 subsequently corresponds to the actual current 24. A defect in a particulate filter connected upstream of the particulate sensor 10 in the exhaust duct is symbolized by the beginning of sooting 23.

[0034] The actual current 24 corresponds to a current flow through the electrodes 12, 13 at an applied measuring voltage and can be measured correctly up to the maximum current 21, as shown in the curve of the measured current 22. The maximum current 21 is predetermined, for example, by a measuring range of an analog-digital converter, which is used to determine the current flow through the electrodes 12, 13 by measuring a voltage across a corresponding Fig. 5 is provided. Due to the heavy sooting of the particle sensor 10, the measured current 22 as the output signal of the particle sensor 10 increases rapidly and reaches the maximum current 21 at the limit of the measurable current range. The actual current profile 24 through the electrodes 12, 13 continues to rise due to the high particle loading. A subsequent regeneration phase 25 burns off the deposited particles 15, and the measured current 22 falls back below the maximum current 21.

[0035] Fig. 4 shows a diagram of the time course of the measured current 22 and an actual current in the case of a short circuit between electrodes 12, 13 of the particle sensor 10. The same identifiers are used as for Fig. 3 introduced used.

[0036] The occurrence of the short circuit is symbolized by a beginning short circuit 27.

[0037] In contrast to the Fig. 3, the actual current 24 does not fall below the maximum current in the event of a short circuit due to regeneration of the particle sensor 10, but remains at its high level.

[0038] A regeneration phase 25 of the particulate sensor 10 can thus distinguish between a short circuit and a heavy particle load in the particulate sensor 10. The disadvantage of this is the high time expenditure, since complete regeneration must be waited for. Due to this waiting time, according to on-board diagnostics legislation, a good message from a particulate filter must be delayed by this time, which contributes to the disadvantage of the OBD-IUMPR (On-Board Diagnostics - In Use Monitor Performance Ratio) for diagnosing the particulate filter. There is also the risk that, in the case of a very badly damaged particulate filter, particles 15 will accumulate again on the electrodes 12, 13 quickly enough, even immediately after the regeneration phase 25, so that a distinction between a short circuit and sooting is no longer possible.

[0039] Fig. 5 shows an electrical circuit for operating a particle sensor 10. The circuit enables the implementation of the method according to the invention for reliably distinguishing between a short circuit and a heavy particle load of the particle sensor 10. Shown are the electrodes 12, 13 of the particle sensor 10, which are designed as comb-like interdigital electrodes. Fig. 6 and Fig. The measurement voltage 51 shown in Figure 7 is provided by a linear voltage source 30. The linear voltage source 30 is represented by an ideal voltage source 31 and a series-connected impedance 32 as an equivalent circuit. The voltage source 30 is connected to ground 45a via its negative terminal, while the positive terminal is connected to the positive electrode 12 of the particle sensor 10 via a positive electrode terminal 43. The negative electrode 13 of the particle sensor 10 is connected via a negative electrode terminal 44 to a current measuring shunt 46, which is connected to ground 45b on one side.

[0040] A voltage divider 40 is connected in parallel with the electrodes 12, 13 and the current measuring shunt 46 between the positive terminal of the voltage source 30 and ground 45c. The voltage divider 40 is composed of a first resistor 41 and a second resistor 42.

[0041] A first analog-to-digital converter 33 determines the voltage drop across the second resistor 42 of the voltage divider 40. A second analog-to-digital converter 34 detects the voltage drop across the current measuring shunt 46.

[0042] During operation of the particle sensor 10, a measuring voltage 51 is applied via the voltage source 30 to the electrodes 12, 13 of the particle sensor 10 and the downstream current measuring shunt 46. As particles 15 adhere to the electrodes 12, 13, they are conductively connected to one another, and a current 24 flows, which is determined by the voltage measurement with the second analog-to-digital converter 34 across the current measuring shunt 46 and evaluated in a downstream control unit (not shown). The measuring range of the second analog-to-digital converter 34 and the resistance of the current measuring shunt 46 determine the measurable current range with a correspondingly resulting maximum current 21.

[0043] The output voltage of the voltage source 30, and thus the voltage at the positive, first electrode 12, is monitored via the voltage divider 40 and the first digital-to-analog converter 33. In the event of a short circuit between the electrodes 12, 13, between the leads to the electrodes 12, 13, or between the positive first electrode 12 and ground 45, the total resistance of the voltage divider 40, connected in parallel with the resistance of the current measuring shunt 46, loads the voltage source 30. The voltage at the positive, first electrode 12 thus collapses according to the impedance 32 of the voltage source 30.

[0044] In the event of a heavy particle load on the particle sensor 10 as a result of a defective particle filter, the resistance of the voltage divider 40 in parallel with the series connection of the current measuring shunt 46 and the sensor element impedance of the electrodes 12, 13 of the particle sensor 10 loads the voltage source 30. Since the sensor element impedance, which is dependent on the particle load, is always well above zero ohms, the load on the voltage source 30 is relatively low, so that the voltage at the positive first electrode 12 hardly drops in accordance with the impedance 32 of the voltage source 30.

[0045] By evaluating the voltage drop between the positive first electrode 12 and ground 45, a clear distinction can be made between a heavy particle load and a short circuit and thus between a defective particle filter and a defective particle sensor 10.

[0046] Fig. Figure 6 shows a double diagram of the time course of a measured current 22, an actual current 23 and a measuring voltage 51 with a high particle load of the particle sensor 10. The same identifiers are used as for Fig. 3 and Fig. 4 introduced used.

[0047] The upper part of the diagram shows the curve of the actual current 23 and the measured current 22 limited by the maximum current 21 when using the particle sensor 10 behind a severely defective particle filter. As already Fig. As shown in Figure 3, the actual current 23 increases sharply with the onset of sooting 23. The measured current 22 is limited by the maximum current 21 as the maximum limit of the measurable current range, while the current 23 actually flowing through the electrodes is above the measurable maximum current 21.

[0048] In the lower part of the diagram is the course of the measuring voltage 51, as it is connected to the Fig. 5, is measured via the second resistor 42 of the voltage divider 40. The measured voltage 51 is plotted against a voltage axis 50 and against a second time axis 53, which has the same division as the time axis 26 in the upper part of the diagram. A voltage threshold 52 is represented by a dashed line.

[0049] With the onset of sooting 23, the actual current 23 increases sharply, placing a load on the voltage source 30. This is reflected in a decrease in the measurement voltage 51. Because the impedance of the particle sensor 10 remains well above zero ohms even at high particle loads, the actual current 23 increases only relatively slightly above the maximum current 21. The load on the current source 30 is therefore so low that the measurement voltage 51 remains above the voltage threshold 52.

[0050] Fig. 7 shows a double diagram of the time course of a measured current 22, an actual current 23 and a measuring voltage 51 in the event of a short circuit between electrodes 12, 13 of the particle sensor 10 or between the supply lines to the electrodes 12, 13. Fig. 7 therefore corresponds to the Fig. 6 in case of a short circuit, the beginning of which is symbolized by a short circuit start 23.

[0051] Due to the short circuit, the electrodes 12, 13 are bridged with very low resistance, which results in a very high actual current 23 and a correspondingly high load on the voltage source 30. This leads to the measuring voltage 51 being lower than that in Fig. 6 shows a significant drop in particle loading and below the voltage threshold 52.

[0052] An evaluation circuit (not shown) or a control electronics unit (not shown) connected downstream of the first analog-to-digital converter 33 checks whether the measured voltage 51, after the measured current has reached the maximum current 21, is above or below the voltage threshold 52. If the measured voltage 51 is above the voltage threshold 52, it can be assumed that the particle sensor 10 is heavily loaded with particles and, therefore, that the particle sensor 10 is intact and the particle filter is severely defective. If, on the other hand, the measured voltage 51 is below the voltage threshold 52, it can be assumed that there is a short circuit between the electrodes 12, 13, the leads to the electrodes 12, 13, or between the leads or the positive electrode 12 and ground 45.

[0053] The device and method thus enable a reliable and rapid distinction between a high particle load in the particle sensor 10 and a short circuit. Unnecessary regeneration phases 25 for the particle sensor 10 can thus be avoided, leading to slower sensor aging. A pass signal for a particulate filter to be monitored can occur earlier, thereby increasing the IUMPR (In Use Performance Ratio). Furthermore, even with a very high particle load in the exhaust gas, there is no risk of confusing a short circuit with a high particle load in the particle sensor 10, as occurs after a regeneration phase 25 of the particle sensor 10.

[0054] In the Fig.In the embodiment shown in Figure 5, the voltage source 30 is represented as a linear voltage source 30 by means of the Thévenin equivalent. Advantageously, a voltage source 30 can also be provided that exhibits non-linearity, so that when a defined load is exceeded, the source voltage itself collapses, thus causing a stronger and correspondingly easier-to-evaluate collapse of the measurement voltage 51 in the event of a short circuit.

Claims

[1] Method for operating a collecting particle sensor (10) for determining the particle content of an exhaust gas, wherein the particle sensor (10) contains at least two electrodes (12, 13), wherein during a measuring phase a measuring voltage (51) provided by a voltage source (30) is applied across the electrodes (12, 13) and a subsequent current measuring shunt (46), wherein, to determine the particle content in the exhaust gas, a change in a current (24) between the electrodes (12, 13) is evaluated by particles (15) deposited on the particle sensor (10) from the exhaust gas, and wherein a measurable current is limited by a maximum current (21), characterized bythat when the maximum current (21) is reached, the measuring voltage (51) is determined and that a control unit concludes that there is a short circuit between the electrodes (12, 13) or the supply lines to the electrodes (12, 13) if the measuring voltage (51) is below a predetermined first voltage threshold (52) and that a high particle loading of the particle sensor (10) is concluded if the measuring voltage (51) is above a predetermined second voltage threshold (52), wherein to determine the current (24) between the electrodes (12, 13) a voltage drop across the current measuring shunt (46) connected in series with the electrodes (12, 13) is determined and that to determine the measuring voltage (51) a voltage drop across a resistor (42) of a voltage divider (40) connected in parallel with the electrodes (12, 13) and the current measuring shunt (46) is determined, wherein the measurable current is determined by the maximum current (21) is limited,in that a first evaluation circuit determines the voltage drop across the current measuring shunt (46) and thus determines the current (24) through the electrodes (12, 13), wherein the maximum current (21) is predetermined by the measuring range of the first evaluation circuit, wherein a second evaluation circuit for voltage measurement is connected in parallel with the resistor (42) of the voltage divider (40) to determine the measuring voltage (51). [2] Method according to claim 1, characterized by that the first voltage threshold (52) corresponds to the second voltage threshold (52). [3] Method according to one of claims 1 or 2, characterized by that a linear voltage source (30) or a non-linear voltage source is used to provide the measuring voltage (51). [4] Method according to one of claims 1 to 3, characterized bythat the internal impedance (32) of the voltage source (30) and / or the total resistance of the voltage divider (40) are adapted to the impedance curve of the particle sensor (10) in such a way that the measuring voltage (51) drops sharply in the event of a short circuit and drops only slightly in the event of a high particle load. [5] Device for operating a collecting particle sensor (10) for determining the particle content of an exhaust gas, wherein the particle sensor (10) contains at least two electrodes (12, 13) to which particles (15) from the exhaust gas accumulate and electrically connect the electrodes (12, 13), with a voltage source (30) for applying a measuring voltage (51) across the electrodes (12, 13) and a current measuring shunt (46) connected in series with the electrodes (12, 13), with a first evaluation circuit for determining a voltage drop across the current measuring shunt (46) for determining a current (24) through the electrodes (12, 13), wherein a maximum measurable current (21) between the electrodes (12, 13) is predetermined by the measuring range of the first evaluation circuit, and with a control unit for determining the particle loading of the particle sensor (10) from the determined current (24) through the electrodes (12, 13), characterized bythat a voltage divider (40) is connected in parallel to the electrodes (12, 13) and the current measuring shunt (46), that for determining the measuring voltage (51) a second evaluation circuit for voltage measurement is connected in parallel to a resistor (42) of the voltage divider (40) and is connected to or integrated in the control unit, that a program sequence or a circuit arrangement for comparing the measuring voltage (51) determined when the maximum current (21) is reached with a predetermined first voltage threshold (52) and a predetermined second voltage threshold (52) is provided in the control unit, and that a program sequence for detecting a short circuit between the electrodes (12, 13) or the leads to the electrodes (12, 13) is provided in the control unit when the determined measuring voltage (51) falls below the first voltage threshold (52) or for detecting a heavy particle load of the particle sensor (10),if the determined measuring voltage (51) exceeds the second voltage threshold (52). [6] Device according to claim 5, characterized by that the first evaluation circuit and / or the second evaluation circuit is each formed by an analog-digital converter (33, 34). [7] Device according to claim 5 or 6, characterized by that the first voltage threshold (52) and the second voltage threshold (52) are equal.

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