WO2009010471A1

WO2009010471A1 - Sensor, method and use thereof for detecting the size distribution of particles in a gas stream

Info

Publication number: WO2009010471A1
Application number: PCT/EP2008/059107
Authority: WO
Inventors: Peter Bartscherer; Ralf Schmidt
Original assignee: Robert Bosch Gmbh
Priority date: 2007-07-17
Filing date: 2008-07-11
Publication date: 2009-01-22
Also published as: DE102007033215A1; EP2171426A1

Abstract

The invention relates to a sensor for detecting the size distribution of particles in a gas stream. Said sensor comprises an electrode system having at least three electrodes (1, 1'; 2, 2'; 3, 3'; 4, 4') lying in a plane, at least one voltage supply device (201; 202; 203; 204) and at least one voltage measuring and/or current measuring device (301; 302; 303; 304). The sensor is characterized in that two electrodes each of different polarity (1, 1'; 2, 2'; 3, 3'; 4, 4') form a pair of electrodes (11; 12; 13; 14), said pair of electrodes (11; 12; 13; 14) being arranged along an imaginary beam (X1, S1), lying in the plane of the electrodes, in such a manner that the beam (X1, S1) extends between the two electrodes (1, 1'; 2, 2'; 3, 3'; 4, 4') of a pair of electrodes (11; 12; 13; 14). The pairs of electrodes (11; 12; 13; 14) arranged along the beam (X1; S1) are connected to at least one voltage measuring and/or current measuring device (301; 302; 303; 304) in such a manner that the voltage and/or the current flowing between every pair of electrodes (11; 12; 13; 14) can be determined individually. The invention also relates to a corresponding method and to the use thereof.

Description

title

Sensor, method and their use for detecting the size distribution of

Particles in a gas stream

description

The present invention relates to a sensor and a method and the use thereof for detecting the size distribution of particles in a gas stream.

State of the art

In the near future, the particulate emissions, especially of vehicles during driving, after passing through an engine or diesel particulate filter (DPF) must be monitored by law (On Board Diagnosis, OBD). In addition, a diesel particulate filter regeneration control load forecast is required to ensure high system safety with few efficient, fuel-efficient regeneration cycles, and to use cost-effective filter materials, such as cordierite.

One possibility for this is provided by resistive particle sensors known from the prior art, in particular resistive particle sensors. Resistive particle sensors draw on the detection of particle ejection caused by particle deposition resistance change of an electrode system with two or more comb-like interdigitated electrodes (interdigital electrode system) zoom.

Due to their mode of operation, resistive particle sensors arrange themselves according to the collecting principles. Such sensors are described by DE 101 493 33 A1 and WO 2003006976 A2.

Currently, resistive particle sensors, especially particle sensors, are conductive

Particles are known in which two or more metallic, comb-like into one another gripping electrodes (interdigital electrodes) are formed, wherein the accumulating under the action of an electrical measuring voltage particles, in particular soot particles, the electrodes short and so with increasing particle concentration on the sensor surface a decreasing resistance (or an increasing current at a constant applied voltage) between the electrodes becomes measurable. After reaching a threshold value, a changing sensor current can be measured, which can be correlated with the increase of the particle mass on the sensor surface. To regenerate the sensor after particle deposition, the sensor must be burned free using an integrated heater.

However, such sensors will respond to any particles attaching to the electrodes regardless of their particle size. Therefore, conventional sensors per se can only determine the particle mass per volume of gas (particle mass per cubic centimeter of air).

The fact that small particles from the mucous membranes in the nasopharynx or the hairs in the nasal area are filtered out only conditionally and thus have a burden on the respiratory tract result, while larger particles are filtered out and thus do not represent a burden on the respiratory tract, is with a Determination of particle mass per cubic centimeter of air not taken into account.

Therefore, the US Environmental Protection Agency (EPA) introduced the Particulate Matter Standard (PM standard), which weights the particle immission as a function of particle size. This PM standard has also been introduced in the European Union. Since the beginning of 2005, the limit value PMio has been observed in the European Union. PMio means that all particles with an aerodynamic diameter of less than 10 μm are included in the weighting. Although ultrafine particles / particles with an aerodynamic diameter of less than 100 nm are considered to be particularly harmful to health, they are underweighted at a PMio weighting.

To determine the PMio value, conventional sensors are equipped with size-selective inlets. With these size-selective inlets, larger particles are masked out by a diversion of the particle-laden gas flow adapted to the size class. By such deflection, however, only particles which have an aerodynamic diameter of about> 300 nm and behave ballistically, can be hidden. The size distribution of harmful, ultrafine particles / particles with an aerodynamic diameter of less than 300, which behave according to the laws of diffusion, can therefore not be determined by size-selective inlets.

Disclosure of the invention

Advantages of the invention

A sensor according to the invention for detecting the size distribution of particles in a gas stream, comprising an electrode system having at least three in-plane electrodes, at least one power supply device and at least one voltage measuring and / or current measuring device, characterized in that in each case two electrodes in the electrode system form a pair of electrodes of different polarity, wherein the electrode pairs are arranged along a lying in the plane of the electrodes fictitious beam, that the beam in each case between the two electrodes of a pair of electrodes, the arranged along the beam pairs of electrodes in such a way at least one voltage measurement and / or current measuring device are connected, that the voltage and / or the current flow between each pair of electrodes can be determined individually, has the advantage that different size fractions of accumulating particles dissolved un d can be measured, whereby size fractions of ultrafine particles / particles with an aerodynamic diameter of less than 300 nm can still be resolved and measured. The division of the size fractions can be determined on the one hand by the configuration of the electrode system. On the other hand, the division of the size fractions can be adjusted by adapting the voltages applied to the electrode pairs during operation. Advantageously, electrode systems according to the invention are also very small and inexpensive to implement and have the potential to be used in motor vehicles.

Further advantages and advantageous embodiments of the subject invention are described in the description, the drawings and the claims.

Brief description of the drawings - A -

Ausführangsbeispiele of the invention are illustrated in the drawings and explained in more detail in the following description.

FIG. 1a shows a schematic representation of a first embodiment of a sensor according to the invention with an electrode system in which

Electrode pairs are arranged along a beam, wherein each electrode pair is connected to its own voltage measuring and / or current measuring device, wherein all pairs of electrodes are connected to a common power supply device and wherein each pair of electrodes has its own variable resistor, which makes it possible at the different pairs of electrodes apply different voltages;

FIG. 1 b shows a schematic representation of a second embodiment of a sensor according to the invention with an electrode system in which pairs of electrodes are arranged along a jet, each of them

Electrode pair is connected to its own voltage measuring and / or current measuring device and to its own power supply device; FIG. 1c shows a schematic illustration of a third embodiment of a sensor according to the invention, which differs from the second one shown in FIG

Embodiment differs in that between adjacent electrodes belonging to different electrode pairs, in each case a further voltage measuring and / or current measuring device is connected, whereby an improved measurement is made possible with a voltage polarity changing from electrode pair to electrode pair;

FIG. 1 d shows a schematic representation of a fourth embodiment of a sensor according to the invention, which differs from the first embodiment shown in FIG. 1 a mainly in that the electrode pair gap distance A between the two electrodes of a pair of electrodes increases continuously from pair of electrodes to pair of electrodes. wherein the arrangement of the electrodes is asymmetrical with respect to the beam passing through the pair of electrode gaps;

FIG. 1 e shows a schematic representation of a fifth embodiment of a sensor according to the invention, which differs from the fourth embodiment shown in FIG. 1 d in that the arrangement of the electrodes is symmetrical with respect to the beam passing through the electrode pair gap;

FIG. 1f shows a schematic representation of a sixth embodiment of a sensor according to the invention, which differs from the first embodiment shown in FIG. 1a primarily in that the

Electrode pair gap distances of the individual pairs of electrodes are optimized with respect to a Gaussian distribution-based particle size distribution;

FIG. 1 g shows a schematic illustration of a seventh embodiment of a sensor according to the invention, which differs from the sixth embodiment shown in FIG

Optimized electrode pair gap distances of the individual pairs of electrodes with respect to a distribution based on a bimodal distribution particle size distribution;

FIG. 1h shows a schematic representation of an eighth embodiment of a sensor according to the invention, which differs from the first one shown in FIG

Embodiment differs in that arranged on one side of the beam electrodes of four adjacent pairs of electrodes are formed as an electrode, wherein arranged on the other side of the beam electrodes are spaced from each other and thereby with the one, located on the other side of the beam electrode four

Electrode pairs forming;

Figure 2a shows a schematic representation of a ninth embodiment of a sensor according to the invention with an electrode system are arranged in the pair of electrodes along radial beams; FIG. 2b serves to illustrate a stagnation flow of the electrode system shown in FIG. 2a with a gas flow;

FIG. 2c shows a schematic representation of a tenth embodiment of a sensor according to the invention with an electrode system in which electrode pairs are arranged along six radial beams, wherein the polarity of the electrodes alternately changes from one radial row of electrodes to the adjacent rows of radial electrodes, and furthermore illustrates that those pairs of electrodes which are arranged on an electrode circuit can be connected to a (common) further voltage measuring and / or current measuring device; Figure 2d shows a schematic representation of an eleventh embodiment of a sensor according to the invention with an electrode system in the Electrode pairs are arranged along six radial beams, wherein the polarity of the electrodes alternately changes both from a row of radial electrodes to the adjacent rows of radial electrodes, and from electrode to electrode within a row of radial electrodes; FIG. 2 e shows a schematic illustration of a twelfth embodiment of a sensor according to the invention, which differs from the tenth embodiment shown in FIG. 2 c mainly in that the electrodes of four adjacent electrode pairs arranged on one side of a beam are each formed as one electrode arranged on the other side of the beam electrodes are spaced from each other and thereby each form four pairs of electrodes with one, located on the other side of the beam electrode;

FIG. 2f shows a schematic representation of a thirteenth embodiment of a sensor according to the invention, which differs from the ninth, tenth and eleventh embodiments shown in FIGS. 2a, 2c and 2d mainly in that the radial beams have a different number of electrode pairs arranged thereon;

Figure 2g shows a schematic representation of a fourteenth embodiment of a sensor according to the invention, which differs from the ninth, tenth, eleventh and thirteenth embodiment shown in Fig. 2a, 2c, 2d and 2f mainly characterized in that arranged on the radial beam electrodes via two opposite circular cutouts extend, with electrode-free circular cutouts being located between these circular cutouts; and

Figure 2h shows a schematic representation of a fifteenth embodiment of a sensor according to the invention, which differs from the ninth, tenth, eleventh, thirteenth and fourteenth embodiment shown in Fig. 2a, 2c, 2d, 2f and 2g mainly characterized in that the number and configuration of arranged on two opposite circular cut-away electrodes are different from each other.

FIG. 1a shows a schematic representation of a first embodiment of a sensor according to the invention with an electrode system in which lies in a plane

Electrode pairs 11; 12; 13; 14 along a in the plane of the electrode pairs 11; 12;

13; 14 lying beam Sl are arranged. The electrodes 1, 1 '; 2, 2 '; 3, 3 '; 4, 4 'of a pair of electrodes 11; 12; 13; 14 according to the invention have a different

Polarity are arranged on different sides of the beam Sl. As part of These and some other embodiments of the present invention are all pairs of electrodes 11; 12; 13; 14 connected via lines 101, 101 'to a common power supply device 201. To apply different voltages to the different pairs of electrodes 11; 12; 13; 14 for dissolving the size distribution of particles in a gas stream according to the invention, each pair of electrodes 11; 12; 13; 14 via its own, variable, known in the series resistor 401; 402; 403; 404th

According to the invention, the electrode pairs 11 arranged along the beam X1 are; 12; 13; 14 such at least one voltage measuring and / or current measuring device 301;

302; 303; 304 that the voltage and / or the current flow between each pair of electrodes can be determined individually. In the context of the embodiment shown in Figure Ia, this is ensured by the fact that each pair of electrodes 11; 12; 13; 14 to a separate voltage measuring and / or current measuring device 301; 302; 303; 304 is connected. In the context of the present invention, however, it is also possible to connect a plurality of electrode pairs arranged along the beam to a (common) voltage measuring and / or current measuring device, wherein the switch is switched between the individual electrode pairs to control the voltage and / or the current flow each individual pair of electrodes to determine.

In a voltage measuring and / or current measuring device 301 according to the invention; 302; 303; 304 may be, for example, a series-connected current measuring device. However, it may also be a voltage meter, which act in parallel to a resistor.

Advantageously, in the context of those embodiments according to the invention, the at least one series resistor may have the function of a voltage measuring and / or current measuring device and a series resistor combined. For example, each known in size dropping resistor, a voltmeter can be connected in parallel, which from a

Particle deposition resulting voltage drop across the respective series resistor measures. Advantageously, such a voltage drop can be used at a known voltage as a measure of accumulated particles.

It is expedient to choose between direct current measurement via the current measuring devices 301; 302; 303; 304 and not here illustrated indirect measurement of the voltage drop across the known series resistors 401; 402; 403; 404 decide. If the series resistors are electronically controllable resistors, then a separate circuit, not shown here, for controlling and / or regulating the respective series resistor 401; 402; 403; 404 necessary.

The electrode pairs 11; 12; 13; 14 are arranged along the beam Sl, that the beam Sl in each case between the two electrodes 1, 1 '; 2, 2 '; 3, 3 '; 4, 4 'of a pair of electrodes 11; 12; 13; 14 runs. Between the electrodes 1, 1 '; 2, 2 '; 3, 3 '; 4, 4 'is therefore an electrode pair gap 6 before. In the context of this embodiment and some further embodiments of the present invention, the electrodes 1; 2; 3; 4 on one side of the beam Sl mirror-symmetrical to the electrodes 1 '; 2 '; 3 '; 4 'on the other side of the beam Sl designed and arranged. The beam Sl can therefore be referred to in the mirror-symmetrical embodiment / s as a symmetry beam Sl.

A "symmetry beam" (denoted by the reference symbol S) in the sense of the present invention, apart from being a ray, that is to say a fictitious line, straight, on one side, for example from the point P, and not a straight line, the same properties as an axis of symmetry, that is, to one

Point Y or object (one electrode of a pair of electrodes) on one side of the beam, there is another, in particular mirror-symmetrical, point Y 'or object' (partner electrode) on the other side of the beam. In this case, the two points Y and Y 'or objects at the same distance from the beam and are arranged such that a connecting distance between the points Y and Y' or

Items from the beam is halved at right angles. A beam which passes through an electrode pair gap and to which the electrodes of the electrode pairs arranged thereon are arranged asymmetrically, however, is designated in the context of the present invention by the reference symbol X.

In order to detect the size distribution of particles in a gas stream, a gas stream 5 comprising particles is moved parallel to the symmetry beam S1, in particular parallel to that between the electrodes 1, 1 '; 2, 2 '; 3, 3 '; 4, 4 'of the electrode pairs 11; 12; 13; 14 lying electrode pair gap 6, as well as parallel to the plane of the electrodes 1, 1 ', 2, 2% 3, 3', 4, 4 'passed or flowed over the electrode system. By the variable

Series resistors 401; 402; 403; 404 are applied to the electrode pairs 11; 12; 13; 14 different voltages applied. The amount of each of a pair of electrodes 11; 12; 13; 14 applied voltages is thereby at each pair of electrodes 11; 12; 13; 14 adapted individually to the expected particle size distribution and / or the gas flow rate. The expected particle size distribution is suitably determined by previously performed adjustment measurements.

The magnitude of the gas flow rate is known in most applications of a sensor according to the invention. For example, the gas flow velocity can be calculated via a signal from an engine or plant control device in accordance with an onflow transfer function. In cases where the gas flow rate is not known, can in a inventive

Sensor an additional device for measuring the gas flow velocity can be integrated. On the basis of the data thus obtained on the expected particle size distribution and / or the gas flow velocity, individual voltages are applied to the individual electrode pairs by a control device.

When the particles in the gas stream 5 flow at a certain gas velocity from one side of the electrode system parallel to the paired electrode gap 6 to the opposite side of the electrode pair gap 6, the particles are separated by electrophoretic forces consisting of the electrode pairs 11; 12; 13; 14 applied voltages, as well as by thermophoresis and diffusion on the

Surface of the electrode system pulled / passed and store between and / or on the electrodes 1, 1 ', 2, 2', 3, 3% 4, 4 '. The place of attachment of the particles depends on the size, mass and charge of the particles, since the particles in the gas flow behave on the one hand according to the laws of diffusion and ballistics, on the other hand according to the laws of electrophoresis.

Due to the electric field resulting from the applied voltages, the particles in the electrode pair gap 6 between the electrodes 1, 1 '; 2, 2 '; 3, 3 '; 4, 4 'aligned and form dendritic structures, each of the one electrode 1; 2; 3; 4 of an electrode pair 11; 12; 13; 14 to the other electrode 1 ';

2 '; 3 '; 4 'of an electrode pair 11; 12; 13; 14 grow. The dendritic growth rate, that is, the growing distance per unit of time, is higher for larger particles than for smaller ones. This is partly due to the fact that a smaller number of larger particles is needed to bridge the same distance as for small particles. On the other hand, larger particles can stretch more strongly through the electric field than smaller particles. As the particle accumulation proceeds, in each case formation takes place between the electrodes 1, 1 '; 2, 2 '; 3, 3 '; 4, 4 'of a pair of electrodes 11; 12; 13; 14

Particle bridges / particle paths, which the respective electrode pair 11; 12; 13; Short circuit 14. In this case, the short circuit of the individual electrode pairs 11 takes place; 12; 13;

14 as a function of the size distribution of the particles present in the gas stream at different times. Since each pair of electrodes 11; 12; 13; 14 via its own voltage measuring and / or current measuring device 301; 302; 303; 304, the short circuits between the individual electrode pairs 11; 12; 13; 14 of the electrode system according to the invention are determined independently and output as a measure of the particle size distribution. In this case, both an evaluation over the tripping time, that is, the period of time that elapses until the electrode pair shows a predetermined resistance due to a particle bridge, as well as an evaluation of the change over time of the voltage, the current and / or the resistance is possible.

This measurement principle according to the invention is applicable both to a gas flow 5 with a constant gas flow velocity and to a gas flow 5 with a variable gas flow velocity. For gas streams 5 with constant gas flow rate can be used, for example, with constant applied voltages. However, for gas streams 5 of variable gas flow rate, the attachment of the respective size fraction may shift from one pair of electrodes to an adjacent pair of electrodes. This can be corrected according to the invention by including the gas flow rate in the evaluation of the measurement.

For example, the measurement at a variable gas velocity becomes constant at the electrode pairs 11; 12; 13; 14 applied voltages carried out and measured the change over time of the resistance and evaluated in dependence on the gas velocity. Alternatively, in the context of the present

Invention a gas velocity change by adjusting the on the electrode pairs 11; 12; 13; 14 applied voltages are corrected. By means of such an immediate correction, the particles deposit again at the electrode pairs determined for the respective particle size and not, as would be the case without correction, at electrode pairs adjacent thereto. Preferably, the amounts of the at the electrode pairs 11; 12; 13; 14 applied voltages adjusted such that in the expected particle size distribution all electrode pairs 11; 12; 13; 14 in the same time range deliver results and / or must be regenerated.

That is, if the size distribution of the particles to be detected, for example, a Gaussian, bimodal or multimodal distribution corresponds, the respectively on the electrode pairs 11; 12; 13; 14 applied voltages independently of each other to the course of the distribution, for example, to the maximum / maximum and / or the / the minimum / minimum of the distribution adjusted. For example, the voltages applied to the electrode pairs are adjusted such that a lower voltage is applied to the electrode pair (s) at which the maximum / maximum distribution is expected than at the other electrode pairs.

For the special case of a Gaussian distribution-based particle size distribution, it has proven to be advantageous if the voltages applied to the electrode pairs continuously decrease from the first pair of electrodes to the electrode pair on which the particle size fraction corresponds to the maximum of the Gaussian distribution and from the Gaussian distribution maximum appropriate

Pair of electrodes to the last pair of electrodes steadily increase the voltages applied to the pairs of electrodes. For example, the amount of voltage from the first electrode pair to the middle electrode pair of an electrode pair row arranged on a beam may steadily decrease and steadily increase from the middle electrode pair to the last electrode pair of an electrode pair row arranged on a beam.

For the further special case that the size distribution of the particles to be detected corresponds to a continuously increasing or decreasing distribution, the voltages can be applied to the respective electrode pairs 11; 12; 13; 14 are applied, that the voltage applied to the electrode pairs continuously change from pair of electrodes to pair of electrodes, that is steadily increase or decrease.

In addition, it is possible, as already explained, to adapt the voltage applied to each pair of electrodes as a function of the mode of operation of the internal combustion engine investigated with the sensor according to the invention and / or the system. Figure Ib shows a schematic representation of a second embodiment of a sensor according to the invention with an electrode system in the electrode pair 11; 12; 13; 14 are arranged along a beam Sl. The second embodiment shown in FIG. 1b differs from the first embodiment shown in FIG. 1a in that each pair of electrodes 11; 12; 13; 14 to its own

Power supply device 201; 202; 203; 204 is connected. These power supply devices 201; 202; 203; 204 allow the application of different voltages to the different electrode pairs 11; 12; 13; 14. Therefore, in the context of this embodiment, it is possible to use resistors 401; 402; 403; 404 are waived for adjusting different voltages. The connection of the

Electrode pairs 11; 12; 13; 14 to the respective own power supply device 201; 202; 203; 204 takes place in the context of the second embodiment via two lines 101, 101 '; 102, 102 '; 103, 103 '; 104, 104 '.

In the context of the first and second embodiment shown in FIGS. 1a and 1b, the different voltages are applied to the electrode pairs 11; 12; 13; 14 applied that those electrodes 1; 2; 3; 4; 1'; 2 '; 3 '; 4 'which are on the same side of the beam Sl, have the same polarity. As a result, electrophoretic forces between adjacent electrode pairs, for example, 1 'and 2' are avoided.

In the context of the present invention, however, it is also possible that those electrodes 1; 2; 3; 4; 1'; 2 '; 3 '; 4 'which are on the same side of the beam S / X, have a different polarity. Such a circuit with one or more polarity changes, for example with one of electrode pair too

Electrode pair along the beam of alternating polarity, has proved to be advantageous in the context of the present invention, as this additional information about the amount of positively charged and negatively charged particles contained in the gas stream can be determined. In a wiring with at least one polarity change, however, the particle addition is not only between the

Electrodes 1, 1 '; 2, 2 '; 3, 3 '; 4, 4 'of a pair of electrodes 11; 12; 13; 14 (that is, in the electrode pair gap 6), but also between two adjacent electrodes 1, 2; 2, 3; 3, 4; 1 ', 2'; 2 ', 3'; 3 ', 4', which are located on the same side of the beam S / X, have a different polarity and thereby different electrode pairs 11; 12; 13; 14 belong. Such a combination of two adjacent electrodes 1, 2;

2, 3; 3, 4; 1 ', 2'; 2 ', 3'; 3 ', 4' located on the same side of a beam S / X, have a different polarity and thereby to different pairs of electrodes 11; 12; 13; 14, in the context of the present invention is referred to as "neighbor electrode pair"1001;1002;1003; 1001 ';1002'; 1003 'to indicate "neighbor electrode pairs"1001;1002;1003; 1001 '; 1002 '; 1003 'of the "electrode pairs" 11, 12, 13, 14, in which the electrodes 1, 1', 2, 2 ', 3, 3', 4, 4 'are arranged on different sides of a beam S / X differ.

Figure Ic illustrates such a third embodiment of a sensor according to the invention with one of electrode pair 11; 12; 13; 14 to electrode pair 11; 12; 13; 14 along a beam Sl of alternating polarity. The hatched shown in Fig. Ic, hatched

Surfaces between the electrodes of a pair of electrodes 11; 12; 13; 14 or a neighboring electrode pair 1001; 1002; 1003; 1001 '; 1002 '; 1003 'represent potential particle paths resulting from particle attachment. To prevent particle attachment between a neighboring electrode pair 1001; 1002; 1003; 1001 '; 1002 '; 1003 ', it is necessary that between the electrodes 1, 2; 2, 3; 3, 4; 1%

2 '; 2 ', 3'; 3 ', 4' of a neighboring electrode pair 1001; 1002; 1003; 1001 '; 1002 '; 1003 'a voltage and / or current measurement is possible. This can be realized by having each neighbor electrode pair 1001; 1002; 1003; 1001 '; 1002 '; 1003 'to its own voltage measuring and / or current measuring device 501, 501'; 502, 502 '; 503, 503 'is connected. In the context of the third embodiment of a sensor according to the invention shown in FIG. 1c, the sensor according to the invention therefore comprises, in addition to the voltage measuring and / or current measuring devices 301; 302; 303; 304 of the electrode pairs 11; 12; 13; 14 additional voltage measuring and / or current measuring devices 501, 501 '; 502, 502 '; 503, 503 'for the adjacent electrode pairs 1001; 1002; 1003; 1001 '; 1002 '; 1003 '.

Instead of or in addition to the application of different voltages to the different electrode pairs 11; 12; 13; According to the invention, some parameters A, B, C, D, E of the configuration of the electrode system illustrated in FIG. 1 d can be varied in order to determine the size distribution of particles in one

Gas flow to dissolve or measure. For example, in the context of the present invention, the distance between the electrodes 1, 1 '; 2, 2 '; 3, 3 '; 4, 4 'of a pair of electrodes 11; 12; 13; 14 (electrode pair gap distance) A, the electrode width B, the distance between adjacent electrode pairs C and / or the electrode length D are varied independently from one electrode pair to the next electrode pair. In addition, according to the invention, the length of the entire electrode system E and the number of electrodes n, for example from 1 to n, can be varied.

In particular, FIG. 1 d shows a schematic illustration of a fourth embodiment of a sensor according to the invention, which differs from the first one in FIG

Figure 1a mainly distinguished by the fact that between the two electrodes 1, 1 '; 2, 2 '; 3, 3 '; 4, 4 'of a pair of electrodes 11; 12; 13; 14 electrode pair gap distance A from electrode pair to electrode pair steadily increased. Alone by this change in the electrode pair gap distance A is an inventive determination of the size distribution of particles in one

Gas flow possible. Therefore, the third embodiment shown in FIG. 1 d, as well as other embodiments according to the invention in which the design parameters A, B, C and / or D of the electrode pairs are varied, do not necessarily each include a variable series resistor 401; 402; 403; 404 for each pair of electrodes 11; 12; 13; 14 or each a power supply device 201;

202; 203; 204 for each electrode pair 11; 12; 13; 14. That is, in the third embodiment shown in FIG. Id, as well as other embodiments according to the invention in which the design parameters A, B, C and / or D of the electrode pairs are varied, the electrode pairs 11; 12; 13; 14 are connected such that on all pairs of electrodes 11; 12; 13; 14 the same voltage is applied.

In general, in the case that at all pairs of electrodes 11; 12; 13; 14 the same voltage is applied: the smaller the ratio of the particle size to the particle charge of a particle, the sooner the particle is deposited on the first of the gas flow overflowed electrode pairs 11, 12 at. Conversely, the greater the ratio of

Particle size for the particle charge of a particle, the sooner the particle is deposited on the last of the gas flow overflowed electrode pairs 13, 14 at.

In the event that the size distribution of the particles to be detected corresponds to a continuously increasing or decreasing distribution, the electrode system according to the invention can be designed such that the electrode pair gap distance A, the electrode width B, the distance between adjacent electrode pairs C and / or the electrode length D of Electrode pair to electrode pair along a beam Xl / Sl increased or decreased, for example, steadily increased or steadily reduced. In the context of the present invention, a variation of the design parameters electrode pair gap distance A, the electrode width B, the distance between adjacent electrode pairs C and / or the electrode length D of the electrode system can be performed mirror-symmetrically or asymmetrically with respect to the beam S / X passing through the electrode pair gaps. FIG. 1d shows, for example, a fourth embodiment according to the invention of a sensor according to the invention with asymmetrically arranged electrode pairs 11 with respect to a beam X1 passing through the pair of electrode gaps 6; 12; 13; 14 or electrodes 1, 1 '; 2, 2 '; 3, 3 '; 4, 4 '.

By contrast, FIG. 1 e shows a schematic representation of a fifth embodiment of a sensor according to the invention, which differs from the fourth embodiment shown in FIG. 1 d in that the arrangement of the electrode pairs 11; 12; 13; 14 or electrodes 1, 1 '; 2, 2 '; 3, 3 '; 4, 4 'is symmetrical with respect to the beam Sl passing through the pair of electrodes 6.

However, in order to be able to individually adjust the resolution of the sensor during operation, it is advantageous to apply to the electrode pairs 11; 12; 13; 14 individual voltages can create. Therefore, it is hereby explicitly pointed out that the fourth embodiment shown in FIG. 1 d and the fifth embodiment according to the invention shown in FIG. 1 e as well as in other embodiments according to the invention have the design parameters A, B, C and / or D of the electrode pairs can be varied, each pair of electrodes 11; 12; 13, 14 to a separate power supply device 201; 202; 203; 204 and / or to a separate variable resistor 401; 402; 403; 404 can be connected. It should be noted, however, that not all explained parameters (A, B, C, D, voltage) are independent of each other. For example, a certain ratio of the electrode widths B of the electrode pairs 11; 12; 13; 14 along a beam Xl / Sl to each other by a certain potential profile of the electrode pairs along the beam Xl / Sl are shown with the same effect of the addition.

In the event that the size distribution of the particles to be detected corresponds to a Gaussian distribution, the electrode system according to the invention can be designed such that the electrode pair gap distance A, the electrode width B, the distance between adjacent electrode pairs C and / or the electrode length D of the individual electrode pairs 11; 12; 13; 14 along a beam Xl / Sl individually on the Maximum and the minima of the Gaussian distribution is adjusted. For example, it has proven to be advantageous in this case if the electrode pair gap distance A from the first electrode pair to the electrode pair at which the particle size fraction corresponding to the maximum of the Gaussian distribution is steadily increased and from this pair corresponding to the Gaussian distribution maximum to the last electrode pair at one Beam arranged electrode pair row steadily reduced. Such an embodiment of the electrode system, in which the electrode pair gap distances A of the individual electrode pairs 11; 12; 13; 14 are optimized with respect to a Gaussian distribution based particle size distribution is shown in Figure 1 f, which is a schematic representation of a sixth embodiment of a sensor according to the invention.

In the event that the size distribution of the particles to be detected corresponds to a bimodal or multimodal distribution, the electrode system according to the invention can be designed such that the electrode pair gap distance A, the electrode width

B, the distance between adjacent pairs of electrodes C and / or the electrode length D of the individual pairs of electrodes along a beam Xl / Sl is adjusted individually to the maxima and the minimum / minimum of the bimodal or multimodal distribution, whereby a more accurate resolution of the relevant areas of a bimodal or multimodal size distribution is possible. Such an embodiment of the

Electrode system in which the electrode pair gap distances A of the individual electrode pairs 11; 12; 13; 14 are optimized with respect to a particle size distribution based on a bimodal distribution, is shown in FIG. 1 g, which is a schematic representation of a seventh embodiment of a sensor according to the invention.

Figure 1h shows a schematic representation of an eighth embodiment of a sensor according to the invention, which differs from the first, shown in Fig. Ia, the first embodiment differs in that arranged on one side of the beam Xl electrodes of four adjacent pairs of electrodes 11; 12; 13; 14 as one

Electrode formed 1 are. In this case, the electrodes 1 'arranged on the other side of the beam X1; 2 '; 3 '; 4 'spaced from each other and each have their own voltage measuring and / or current measuring device 301; 302; 303; 304. In addition, the spaced-apart electrodes 1 '; 2 '; 3 '; 4 'is a different polarity than the arranged on the other side of the beam Xl electrode 1 and thus each form an inventive electrode pair 11; 12; 13; 14 with the electrode 1 located on the other side of the beam Xl.

Figure 2a shows a schematic representation of a ninth embodiment of a sensor according to the invention with an electrode system in the electrode pair along radial rays, in particular along eight rays, Sl; S2; S3; S4; S5; S6; S7; S8 are arranged.

In the context of the present invention, the term "beam" is understood to mean only those imaginary straight lines which are bounded on one side by the point P and extend on the other side to infinity, which extend between electrodes having a different polarity All other notional straight lines, which are bounded on one side by the point P and on the other side into the., and have on a common voltage measuring and / or current measuring device

With reference to Fig. 2a, this means that those electrodes which lie along a non-dashed line Sl; S2; S3; S4; S5; S6; S7; S8, which are arranged radially outwardly from the point P, do not have a common voltage measuring and / or current measuring device, which is also not necessary in the case of a circuit shown in FIG.

Figure 2a shows that the beam Sl; S2; S3; S4; S5; S6; S7; S8 lie in the plane of the electrode / electrode pairs and extend radially from a common point P such that all adjacent beams Sl; S2; S3; S4; S5; S6; S7; S8 include the same angle. Along each of the eight streams Sl; S2; S3; S4; S5; S6; S7; S8 are each four electrode pairs 11, 12, 13, 14 to 81, 82, 83, 84 arranged such that the respective beam (for example, Sl) in each case between the two electrodes (for example, 1, 1 ', 2, 2'; 3 ', 4, 4') of the electrode pairs arranged on it (for example 11, 12, 13, 14). In addition, the electrodes (for example 1, 1 ', 2, 2', 3 ', 3', 4 ', 4') arranged to the two sides of a beam (for example S 1) are mirror-symmetrical to one another, the beam (for example S 1) being the axis of symmetry represents. The rays Sl; S2; S3; S4; S5; S6; S7; S8 are thus in the context of this embodiment Symmetriestrahle. FIG. 2 a shows that at all the beams S 1; S2; S3; S4; S5; S6; S7; S8 the same number of electrode pairs n is arranged. In addition, Figure 2a shows that the electrode pairs 11; 21; 31; 41; 51; 61; 71; 81, which on the respective symmetry beams Sl; S2; S3; S4; S5; S6; S7; S8 represent the first pair of electrodes counted outwards from the point P, that is, which form the innermost electrode pair circle, have the same configuration and the same distance with respect to the point P. Similarly, the second 12; 22; 32; 42; 52; 62; 72; 82, third 13; 23; 33; 43; 53; 63; 73; 83 and fourth 14; 24; 34; 44;

54; 64; 74; 84 electrode pairs of the symmetry beam S1; S2; S3; S4; S5; S6; S7; S8, that is, the electrode pairs which form the second, third and fourth electrode pair circle, each have the same configuration and the same distance with respect to the point P. For reasons of clarity, the voltage measuring and / or current measuring devices, power supply device (s) and / or

Series resistors and electrical lines of the electrodes 1, V to 4g, 4g 'not shown in Figure 2a.

The illustrated in Figure 2a, radial electrode system with several, in particular eight, beams Sl; S2; S3; S4; S5; S6; S7; S8 is based on the same construction and measuring principle as the electrode systems explained in FIGS. 1a to 1h with only one jet S1 / X1. If, for example, only the electrode pairs 11 are considered; 12; 13, 14 and the symmetry beam Sl and fades the remaining seven symmetry beam S2; S3; S4; S5; S6; S7; S8 and the electrode pairs 21, 22, 23, 24 to 81, 82, 83, 84 arranged thereon, the result is an electrode arrangement which is analogous to that in FIGS

Ia to Ih is shown electrode arrangement. The parameters (A, B, C, D, E, n, voltage) explained in connection with FIGS. 1a to 1h can therefore also be varied analogously in the case of a radial electrode system according to the invention.

Such a radial electrode system according to the invention is suitable for a

Stagnation point inflow suitable. In the context of the present invention, the term "stagnation point flow" is understood to mean the flow of an electrode system perpendicular to the plane of the electrode system, as shown in Figure 2a, for a stagnation point inflow the electrode pair gaps must be arranged essentially radially symmetrically around the stagnation point Therefore, when flowing through a radial electrode system shown in FIG. 2 a, the gas flow should be oriented so that the stagnation point of the gas flow is at the point P.

FIG. 2b serves to illustrate a stagnation flow of the gas flow shown in FIG. 2a according to the invention, radial electrode system. Of the Gas flow striking the point P of the electrode system is deflected by the electrode system and / or the surface on which the electrode system is arranged in such a way that it flows radially outward from the point P and at the same time substantially parallel to the electrode system plane. Since the pairs of electrodes are radially aligned on the respective beams, the gas flow also flows parallel to the

Radiation and the electrode pair gaps.

FIG. 2c shows a schematic representation of a tenth embodiment of a sensor according to the invention with an electrode system in which electrode pairs are arranged along radial beams S1, S2, S3, S4, S5, S6.

The electrode system shown in Fig. 2c differs from the electrode system shown in Fig. 2a mainly in that the electrode polarity of an electrode row formed radially outward from the point P (for example, 1 ', 2', 3% 4 ') to the adjacent from the point P radially outwardly formed electrode rows

(For example, 1, 2, 3, 4 and Ia, 2a, 3a, 4a) alternately changes. As a result, through all electrode gaps extending radially outward between the rows of electrodes, beams S1, S2, S3, S4, S5, S6 run within the meaning of the present invention, on which pairs of electrodes according to the invention are arranged, between which particles can accumulate, and shows by way of example the wiring of the outer

Electrodes. In order to be able to detect the particle attachment, it is necessary that in each case between all adjacent electrodes of an electrode circuit, a voltage and / or current measurement is possible. This can be realized, on the one hand, by connecting all adjacent electrodes of an electrode circuit in pairs to a separate voltage measuring and / or current measuring device, which, however, results in a large number of voltage measuring and / or current measuring devices and thus a complicated and expensive construction. On the other hand, due to the symmetry of the electrode system shown, this can be realized by interconnecting all the electrodes of an electrode circuit with negative polarity and in each case all electrodes of an electrode circuit with positive polarity and to a common voltage measuring and / or current measuring device (301, 302, 303 not shown for clarity) 304 are connected. Such interconnection of the negative and positive electrodes of a circuit has been found to be particularly advantageous in the context of the present invention, since in this way the number of voltage measuring and / or current measuring devices and electrical

Reduced lines and the measuring surface / the measuring signal can be increased. The beams S1, S2, S3, S4, S5, S6 extend in a manner analogous to the ninth embodiment shown in FIG. 2a in such a way radially from a common point P that all adjacent beams S1; S2; S3; S4; S5; S6 enclose the same angle. Along each of the six streams Sl; S2; S3; S4; S5; S6 are each four electrode pairs 11, 12,

13, 14 to 61, 62, 63, 64 arranged such that the respective beam (for example Sl) in each case between the two electrodes (for example 1, 1 ', 2, 2', 3, 3 ', 4, 4') of arranged on it electrode pairs (for example 11, 12, 13, 14) extends. In contrast to the ninth embodiment shown in FIG. 2a, in the context of this embodiment in each case one electrode is a component of two electrode pairs. That is, an electrode disposed between a first and a second beam forms a first electrode pair with an electrode of the same electrode circuit arranged on the other side of the first beam and a second electrode pair with an electrode of the same electrode circuit arranged on the other side of the second beam. For example, the electrode V forms both a pair of electrodes 11 with the electrode 1 and a pair of electrodes 41 with the electrode Ia.

For the sake of clarity, with the exception of the voltage measuring and / or current measuring devices 304, the voltage measuring and / or current measuring devices, power supply device (s) and / or series resistors and electrical

Lines of the electrodes 1, V to 4b, 4b 'not shown in Figure 2c.

Figure 2d shows a schematic representation of an eleventh embodiment of a sensor according to the invention with an electrode system are arranged in the pair of electrodes along six radial beams. The reference numbers for the individual

Electrodes correspond to those in FIG. 2 c, but are not repeated in FIG. 2 d for reasons of clarity.

The electrode system shown in Fig. 2d differs from the electrode system shown in Fig. 2c mainly in that in addition to the alternating

Polarity change of the electrode rows formed from point P radially outward and the polarity of the electrodes alternately within an electrode row formed radially outward from the point P.

This has the consequence that, in analogy to that described in the context of Figure Ic

Mechanism, also between neighboring pairs of electrodes (two adjacent electrodes, which are on the same side of a beam S / X, have a different polarity and belong to different electrode pairs separated by a circular-like electrode gap) (for example 1001, 1002, 1003) of an electrode row (for example 1 , 2, 3, 4) particle deposition takes place. To the particle attachment between a

In order to be able to detect adjacent electrode pairs (for example 1001, 1002, 1003), it is necessary for a voltage and / or voltage to be applied between the electrodes (for example 1, 2, 2, 3, 3, 4) of a neighboring electrode pair (for example 1001, 1002, 1003). or current measurement is possible. This can be realized by having each neighboring electrode pair (for example 1001, 1002, 1003) on its own

Voltage measuring and / or current measuring device (not shown) is connected.

In the context of the eleventh embodiment of a sensor according to the invention shown in FIG. 2 d, the sensor according to the invention therefore comprises, in addition to the voltage measuring and / or current measuring device of the electrode pairs according to the invention (for example

1, 2, 3, 4) additional voltage measuring and / or current measuring device for the adjacent electrode pairs according to the invention (for example 1001, 1002, 1003).

As explained in connection with the tenth embodiment, due to the symmetry of the electrode system also in the eleventh embodiment, all the electrodes of a negative polarity electrode circuit and all electrodes of a positive polarity electrode circuit can be interconnected and connected to a common voltage measuring and / or current measuring device.

The rays Sl, S2, S3, S4, S5, S6 extend analogously to the ninth and tenth, in

2a and 2c, in such a way radially from a common point P that all adjacent beams Sl; S2; S3; S4; S5; S6 enclose the same angle. Along each of the six streams Sl; S2; S3; S4; S5; S6 are each four electrode pairs 11, 12, 13, 14 to 61, 62, 63, 64 arranged such that the respective beam (for example, Sl) in each case between the two electrodes (for example, 1, 1 ';

2, 2 '; 3, 3 ', 4, 4') of the electrode pairs arranged on it (for example 11, 12, 13, 14). In contrast to the ninth and tenth embodiments shown in FIGS. 2a and 2c, in the context of this embodiment in each case one electrode is part of two electrode pairs and one or two adjacent electrode pairs. That is, an electrode disposed between a first and a second beam forms the same with an electrode disposed on the other side of the first beam Electrode circuit, a first pair of electrodes, with an arranged on the other side of the second beam electrode of the same electrode circuit, a second pair of electrodes and with an arranged on the same side of the first beam electrode of an adjacent electrode circle, a first adjacent electrode pair and / or with one on the same side of the first beam disposed electrode of the other adjacent

Electrode circle a second neighbor electrode pair. For example, the electrode 2 'forms a pair of electrodes 12 with the electrode 2, a pair of electrodes 42 with the electrode 2a, a neighboring electrode pair 1001' with the electrode 1 and a neighboring electrode pair 1002 'with the electrode 3.

For reasons of clarity, the voltage measuring and / or current measuring devices, power supply device (s) and / or series resistors and electrical lines of the electrodes 1, 1 'to 4b, 4b' are not shown in FIG. 2d.

FIG. 2e shows a schematic representation of a twelfth embodiment of a sensor according to the invention, which differs from the tenth embodiment shown in FIG. 2c mainly in that each of the electrodes arranged on one side of a beam (for example X1) consists of four adjacent (for example 11; 12, 13, 14) electrode pairs are formed as one electrode (for example 1). In each case, the electrodes arranged on the other side of the beam (for example 1 ', 2', 3 ', 4') are arranged at a distance from each other, wherein the spaced-apart electrodes (for example 1 ', 2', 3 ', 4') overlap have separate voltage measuring and / or current measuring device. As explained in connection with the tenth and eleventh embodiments, all electrodes (for example 1 ', 1a', 1b ', 1c') arranged at a distance from one another can be interconnected and connected to a common voltage measuring and / or current measuring device arranged electrodes (for example, 1 ', 2', 3 ', 4') also have a different polarity than the electrode located on the other side of the respective beam (for example Xl)

(For example 1) and thus each form an electrode pair according to the invention (for example 11, 12, 13, 14) with the electrode (for example 1) located on the other side of the respective beam (for example X1).

Figure 2f shows a schematic representation of a thirteenth embodiment of a sensor according to the invention, extending from the ninth, tenth and eleventh, in Fig. 2a, 2c and 2d differs mainly in that the radial beams have a different number of pairs of electrodes arranged thereon. Such an embodiment of the electrode system according to the invention has proven to be advantageous in that way as the area required for the electrode system can be optimally utilized.

Figure 2g shows a schematic representation of a fourteenth embodiment of a sensor according to the invention, which differs from the ninth, tenth, eleventh and thirteenth embodiment shown in Fig. 2a, 2c, 2d and 2f mainly differs in that arranged on the radial beams via electrodes two opposite sections of the circle 2001; 2002, between these circular cut-off electrode-free circular cutouts 3001; 3002 lie. Advantageously, this also allows the electrode system to be adapted to the available area. In addition, such an arrangement of circular sections 2001; 2002 with respect to the production proved to be advantageous, since the use of screen printing process, the production of narrow structures which are arranged perpendicular to the Siebdruckrackrichtung, difficult.

Figure 2h shows a schematic representation of a fifteenth embodiment of a sensor according to the invention, which differs from the ninth, tenth, eleventh, thirteenth and fourteenth embodiment shown in Fig. 2a, 2c, 2d, 2f and 2g mainly characterized in that the number and configuration of on two opposite sections of the circle 2001; 2002 arranged electrodes differ from each other. As already explained, such a configuration is due to an optimization of the electrode system surface as well as due to the

Production process advantageous. In addition, such a configuration of the electrode system according to the invention has proved to be advantageous if the gas flow preferably flows in a certain direction (for example in the direction of the jet S2 with the higher number of electrode pairs) due to the geometry of the sensor.

The present invention relates to a sensor for detecting the size distribution of particles in a gas stream, comprising - an electrode system having at least three in-plane electrodes,

- At least one power supply device and - At least one voltage measuring and / or current measuring device, characterized in that

two electrodes of different polarity form a pair of electrodes in the electrode system, the pairs of electrodes being arranged along a notional jet lying in the plane of the electrodes such that the beam extends in each case between the two electrodes of an electrode pair,

- Wherein the electrode pairs arranged along the beam are connected to at least one voltage measuring and / or current measuring device such that the voltage and / or the current flow between each electrode pair can be determined individually.

The pairs of electrodes arranged along the beam can be connected to at least one voltage measuring and / or current measuring device such that the voltage and / or the current flow between each individual electrode pair can be determined by each pair of electrodes arranged along the beam being connected to a separate voltage measuring and / or measuring device. or current measuring device is connected; and / or a plurality of electrode pairs arranged along the beam are connected via a switch to a common voltage measuring and / or current measuring device, wherein the switch is switched between the individual electrode pairs in order to determine the voltage and / or the current flow of each individual pair of electrodes.

For example, such a switch may be a relay.

Advantageously, it is possible with such a sensor according to the invention and the method according to the invention to determine both the resolution of different size fractions of the accumulating particles and the concentration of particles located in a gas stream per size fraction.

In the context of the present invention, the term "beam" is understood to mean a geometric beam, that is to say a fictitious straight line, which is bounded on one side, for example from the point P, and extends on the other side to infinity In the present invention, the term "beam" is understood to mean only those geometrical beams which extend between electrodes having a different polarity and via a common beam Have voltage measuring and / or current measuring device and thereby represent an inventive electrode pair. In the sense of the present invention, a different polarity of the two electrodes of an electrode pair is understood to mean that a potential difference exists between the two electrodes of an electrode pair. The potential difference between the two electrodes of a pair of electrodes may, for example, be zero to plus, plus to minus, minus to zero, plus to higher plus or minus to stronger minus.

For the purposes of the present invention, the term "particles" is understood as meaning solid and / or liquid conductive particles, for example conductive particles and / or droplets, in particular carbon black particles, for example semiconducting carbon.

As explained in detail in connection with the figures, the invention is based on the principle that the location of the attachment of particles to the electrodes depends on the size, mass and charge of the particles and the particles in the gas stream at

Overflow of an electrode system according to the invention on the one hand, the laws of diffusion and ballistics, on the other hand, the laws of electrophoresis behave accordingly. By skillfully exploiting these laws and corresponding dimensioning of the electrodes and voltages applied thereto, not only particles as such, but also the size distribution of the particles, can thus be detected by means of an electrode system according to the invention.

An electrode system according to the invention may have at least two beams lying in the plane of the electrodes, which extend radially from a common point P and along which pairs of electrodes are arranged such that the respective beam extends in each case between the two electrodes of the electrode pairs arranged on it.

According to the invention, the at least two beams can be radial in such a way from the common point P that all adjacent beams are approximately the same

Include angle. This roughly means that the angular deviation can be up to 30%, for example up to 20%, in particular up to 15%.

In addition, the at least two beams lying in the plane of the electrodes can extend radially from a common point P in such a way that the electrodes arranged thereon extend over two, for example opposite, cutouts of one extend substantially round surface, wherein between these cutouts are electrode-free faces.

If the electrode system according to the invention has at least two beams which extend radially from a common point P, those have

Electrode pairs along the respective beams are the first, second, ... or n-th pairs of electrodes, each having substantially the same configuration and / or the same distance with respect to the point P, wherein the numbering of the electrode pairs from the point P starting radially away.

In the context of the present invention, the electrode pairs, which are arranged along the respective beams extending radially from a common point P as respective first, second, third,... N-th pairs of electrodes, are also used as electrode pairs of the first, second, third , ... n-th electrode circuit called. Therefore, those electrode pairs based on the same invention

Electrode circuit are arranged, each having substantially the same configuration and / or the same distance with respect to the point P. In the context of the present invention, essentially deviations from the absolute symmetry or parallelism may amount to up to 30%, for example up to 20%, in particular up to 15%.

Insofar as the electrode system is such a symmetrical, radial electrode system with at least two beams extending radially from a common point P, those electrode pairs which are the first, second,... Or n-th electrode pairs along the respective beams can be used in the context of the present invention are each connected to a common voltage measuring and / or current measuring device and / or power supply device, wherein the numbering of the electrode pairs takes place starting from the point P radially outward.

If the electrode system according to the invention has at least two beams which extend radially from a common point P, the same number of electrode pairs n can be arranged along all the beams in the context of the present invention. The two electrodes of a pair of electrodes arranged along a beam can each be designed and / or arranged substantially mirror-symmetrically to one another, wherein the beam extending between the two electrodes of an electrode pair forms the mirror axis. Preferably, the mutually facing surfaces of the electrodes of a pair of electrodes are arranged substantially parallel to each other.

Electrode pairs arranged along a beam are preferably arranged substantially parallel to one another along the symmetry beam. The electrodes of the electrode pairs are preferably designed such that those surfaces of the electrodes, which face the adjacent electrode pairs, extend substantially parallel to the surfaces of the adjacent electrode pairs. That is, preferably, the mutually facing surfaces of the electrodes of a neighboring electrode pair are arranged substantially parallel to each other.

In the present invention, two or more electrodes disposed on one side of a beam may be formed as one electrode, and the electrodes disposed on the other side of the beam are spaced apart from each other, a polarity other than the electrode disposed on the one side of the beam exhibit. The electrodes arranged on the other side of the beam form in each case a pair of electrodes with the electrode arranged on one side of the beam, the pairs of electrodes arranged along the beam being connected to at least one voltage measuring and / or current measuring device such that the voltage and / or or the current flow between each electrode pair can be determined individually. For example, each electrode pair arranged along the beam, in particular each of the electrodes arranged at a distance from one another on the other side of the beam, can be connected to a separate voltage measuring and / or current measuring device; and / or a plurality of electrode pairs arranged along the beam, in particular a plurality of electrodes arranged at a distance from one another on the other side of the beam, can be connected via a switch to a common voltage measuring and / or current measuring device, the switch being switched between the individual electrode pairs determine the voltage and / or current flow of each pair of electrodes. This manner of designing an electrode system according to the invention can be carried out both in a single-beam electrode system according to the invention and in a multi-beam electrode system according to the invention. An electrode system according to the invention may comprise at least four, for example at least five, six, seven, eight, nine or ten in-plane electrodes.

At least three, for example at least four or at least five, in particular at least six or at least seven pairs of electrodes may be arranged along a beam according to the invention. That is to say, if the electrode system according to the invention has a beam lying in the plane of the electrodes, then at least three, for example at least four or five, in particular at least six or seven pairs of electrodes can be arranged along this beam such that the beam respectively between the two electrodes of a Pair of electrodes runs. If the electrode system according to the invention has a plurality of beams extending in the plane of the electrodes and extending from a common point P, at least three, for example at least four or five, in particular at least six or seven pairs of electrodes can be arranged along these beams such that the respective one Beam in each case between the two electrodes of the electrode pairs arranged on it runs.

In the context of the present invention, an electrode system according to the invention may, for example, have at least three, for example at least four or five or six or seven or eight beams lying in the plane of the electrodes and extending from a common point P.

In a sensor according to the invention, the electrode pair gap distance (distance between the two electrodes of an electrode pair) may be the same for each electrode pair, or the electrode pair gap distance may vary for each electrode pair of a beam. Since large particles bridge a distance with the same number of particles faster than small particles and the exceeding of a threshold by a pair of electrodes the regeneration of the entire electrode system result, it has been found in the present invention to design the electrode pair gap distance at each pair of electrodes such that in the case of the expected particle size distribution, all electrode pairs deliver and / or regenerate measurement results in the same time range. That is, when the size distribution of the particles to be detected corresponds to, for example, a Gaussian, bimodal, or multimodal distribution, the electrode pair gap distance of each pair of electrodes will be individually related to the distribution, such as peak / maximum and / or peak Minimum / minimum of distribution adjusted. For example, the

Electrode pair gap distance in each pair of electrodes are selected such that this at the / n pair of electrodes / s where the maximum / maximum of the distribution is expected to have a greater distance than the other electrode pairs.

For the special case of a Gaussian distribution-based particle size distribution, it has been found to be advantageous if the electrode pair gap distance from the first electrode pair to the electrode pair at which the particle size fraction is detected, which corresponds to the maximum of the Gaussian distribution, of an electrode pair row arranged on a beam increases continuously and from this the Gaussian distribution maximum corresponding electrode pair to the last electrode pair of a pair of electrodes arranged on a beam continuously reduced. For example, the electrode pair gap distance from the first electrode pair to the middle electrode pair of an electrode pair row arranged on a beam can steadily increase and steadily decrease from the middle electrode pair to the last electrode pair of an electrode pair row arranged on a beam.

In the event that the size distribution of the particles to be detected corresponds to a continuously increasing or decreasing distribution, the electrode system according to the invention can be configured in such a way that the electrode pair gap distance increases or decreases continuously along a beam.

Moreover, in a sensor according to the invention, the electrodes may have a uniform electrode width, or the electrode width may vary with each electrode pair of a beam. A large electrode width advantageously leads to a stronger signal, but is accompanied by a broader spectrum of the accumulating particles and thus with a smaller size resolution. The distance between the electrode pairs may be equidistant in a sensor according to the invention or may be different between each pair of adjacent electrode pairs of a beam. Furthermore, in a sensor according to the invention, the electrodes may have a uniform electrode length or the electrode length can vary with each electrode pair of a beam. Preferably, in a sensor according to the invention, the electrode widths and / or electrode lengths and / or the distances between the electrode pairs are adapted to the expected particle size distribution and / or flow rate. That is, the electrode widths and / or electrode lengths of the individual electrode pairs and / or the

Distances between the electrode pairs are adjusted individually to the course of the expected particle size distribution, for example to the maximum / maximum and / or the minimum / minimum of the particle size distribution.

The power supply can in the context of the present invention on two different

Done way. On the one hand, in the case of an electrode system in which the electrode pairs are configured and / or arranged differently, it is sufficient to apply the same voltage to a plurality or all of the electrode arms through a voltage supply device, since the determination of the size distribution of particles in this case is solely due to the embodiment of the invention

Electrode system can be guaranteed. On the other hand, as already explained, it is advantageous to regulate the division of the size fractions by adapting the voltages applied to the electrode pairs during operation and to be able to adapt the measurement to the gas flow velocity.

The application of different and adaptable voltages can be effected according to the invention by connecting two or more electrode pairs to their own power supply device and / or by connecting two or more pairs of electrodes to a common power supply device, wherein the electrode pairs each have their own series resistor

Setting an individual voltage. The fact that two or more pairs of electrodes are connected to a common power supply device, wherein the pairs of electrodes each have their own series resistor for setting an individual voltage, has the advantage that the number of power supply devices are lowered. Preferably, everyone will

Series resistor connected in parallel with a voltmeter. Advantageously, this combination of a series resistor and a voltage measuring device connected in parallel serves both as a voltage measuring and / or current measuring device according to the invention and as a series resistor according to the invention, since from a voltage drop measurement on a known series resistor advantageously the electrical resistance, the current flow through the particle paths can be calculated.

The connection of the electrodes of the electrode system to voltage measuring and / or current measuring devices, power supply devices and / or series resistors via lines. Each electrode of the electrode system preferably has its own line for connection to the voltage supply, voltage measuring and / or current measuring device common to at least the electrode pair partner.

In the context of the present invention, however, it is also possible to connect electrodes of different pairs of electrodes to one another via lines. In the context of one embodiment of the invention, therefore, only one electrode of each electrode pair in the electrode system has its own line for connection to the voltage measuring and / or current measuring device and / or the voltage supply device and / or the series resistor

Electrodes (electrode pair partners) are placed on a common potential. Such a connection has the advantage that thereby the number of lines can be reduced.

In the context of the present invention, the two electrodes of an electrode pair of the electrode system are respectively connected to the voltage supply device in such a way that they have a different polarity relative to one another.

In the context of the present inventions, the voltage supply device (s) can be connected to the respective electrode pairs in such a way that a potential of the same polarity is applied to the electrodes which are arranged on the same side of a beam.

If the electrode system according to the invention is an inventive radial electrode system, the

Power supply device (s) may be connected to the pairs of electrodes of the respective beams such that all adjacent electrodes arranged on different beams have the same polarity.

If the electrode system according to the invention is an inventive radial electrode system, the Voltage supply device (s), however, also be connected to the pairs of electrodes of the respective beams such that the polarity of a row of electrodes radially outwardly from the point P alternates with the adjacent electrode rows formed radially outward from the point P.

In the context of the present invention, moreover, it is possible for those electrodes which are arranged on the same side of a beam to have a different polarity. For example, the polarity of the electrode pairs may alternate along the beam. In a wiring with at least one polarity change, the particle deposition takes place not only between the electrodes of a pair of electrodes, but also between two adjacent, arranged on the same side of a beam electrodes of different polarity, which are referred to in the context of the present invention as a neighboring electrode pair. In order to be able to measure the signal resulting from this particle deposition, in a preferred embodiment of the invention, each neighboring electrode pair is connected to at least one voltage measuring and / or current measuring device such that the voltage and / or the current flow between each adjacent electrode pair can be determined individually a neighbor electrode pair is a pair of two adjacent electrodes of different polarity arranged on the same side of a beam. For example, for each adjacent electrode pair may be connected to its own voltage measuring and / or current measuring device; and / or a plurality of neighboring electrode pairs can be connected via a switch to a common voltage measuring and / or current measuring device, wherein the switch is switched between the individual neighboring electrode pairs in order to determine the voltage and / or the current flow of each individual neighboring electrode pair.

Appropriately, in the context of the present invention, an evaluation device is connected to the voltage and / or current measuring devices.

In addition, a sensor according to the invention may comprise a control device for controlling the voltage supply device (s) and / or variable series resistors, which can be used to apply individual voltages to the individual electrode pairs on the basis of data on the expected particle size distribution and / or the

Gas flow rate controls. Furthermore, a sensor according to the invention may comprise a heating device and / or a temperature measuring device.

The electrodes according to the invention may comprise a metal such as platinum, copper, silver, gold, iron,

Cobalt, nickel, palladium, ruthenium, iridium or rhodium, or a metal alloy, in particular a metal alloy comprising platinum, copper, silver, gold, iron, cobalt, nickel, palladium, ruthenium, iridium and / or rhodium. Preferably, the electrodes comprise platinum.

In addition, a sensor according to the invention may further comprise at least one protective tube which directs the gas flow parallel to the plane of the electrode system and parallel to the symmetry beam (s).

Another object of the present invention is a method for detecting the size distribution of particles in a gas stream with a sensor according to the invention by a voltage is applied to the electrode pairs of the electrode system or to the electrode pairs of the electrode system in each case independent voltages are applied, wherein accumulate particles in that the change in the voltage and / or the current and / or the electrical resistance between the two electrodes of a pair of electrodes at each pair of electrodes resulting from particle accumulation is measured individually and the size distribution of the particles and / or the particle concentration and / or the particle mass flow are evaluated by evaluating the Changes in the voltage and / or the current and / or the electrical resistance of the respective pairs of electrodes is determined.

The application of mutually independent voltages to the electrode pairs of the electrode system has the advantage that the division of the attached to the respective electrode pairs particle size fractions can be easily, quickly and selectively adjusted by targeted adjustment of the respective voltages. Therefore, in the context of the inventive method to the electrode pairs of the electrode system in each case independent voltages can be applied so that each voltage applied to a pair of electrodes for each pair of electrodes is individually adapted to the expected particle size distribution and / or the gas flow rate. Preferably, each of the

Electrode pairs applied voltages adjusted so that deliver all the electrode pairs in the same time range measurement results and / or regenerated at the expected particle size distribution.

That is, when the size distribution of the particles to be detected corresponds to, for example, a Gaussian, bimodal or multimodal distribution, the voltages applied respectively to the electrode pairs become independent of each other in the course of the distribution, for example to the maximum / maximum and / or adjusted the minimum / minimum of the distribution. For example, the voltages applied to the electrode pairs are adjusted so that on the / the one

Electrode pair / s, where the maximum / maximum of the distribution is expected, a lower voltage is applied than at the other electrode pairs.

For the special case of a Gaussian distribution-based particle size distribution, it has proved to be advantageous if from the first pair of electrodes to the

Electrode pair, on which the particle size fraction is detected, which corresponds to the maximum of the Gaussian distribution, the voltages applied to the electrode pairs steadily decrease and from the Gaussian distribution maximum corresponding pair of electrodes to the last pair of electrodes, the voltages applied to the electrode pairs steadily increase. For example, the amount of voltage from the first

Pair of electrodes to the middle electrode pair of a pair of electrodes arranged on a beam steadily sink and steadily rise from the middle pair of electrodes to the last pair of electrodes of a pair of electrodes arranged on a beam.

For the further special case that the size distribution of the particles to be detected corresponds to a continuously increasing or decreasing distribution, the voltages applied respectively to the electrode pairs are adjusted in such a way that the voltage applied to the electrode pairs continuously changes from electrode pair to electrode pair, that is, increases continuously or shrink. In addition, it is possible, as already explained, to adapt the voltage applied to each pair of electrodes as a function of the mode of operation of the internal combustion engine investigated with the sensor according to the invention and / or the system.

In the context of the method according to the invention can voltages to the

Electrode pairs of a beam are applied so that arranged on the same side of a beam electrodes have the same polarity. In the context of the method according to the invention, however, voltages can also be applied to the electrode pairs of a beam in such a way that the polarity of the electrode pairs alternates along the beam.

For example, voltages may be applied to the electrode pairs of two or more beams so that all the adjacent electrodes arranged on different beams have the same polarity.

However, the voltages may also be applied to the electrode pairs of two or more beams such that the polarity of an electrode row formed radially outward from the point P alternates with the adjacent rows of electrodes formed radially outward from the point P.

In addition, voltages may be applied to the electrode pairs of a beam such that the polarity of the electrode pairs alternate along a beam.

The setting of mutually independent voltages on the electrode pairs can, as already explained, be carried out by each arranged along a beam

Electrode pair has its own power supply device or its own variable resistor.

Preferably, the change of the voltage and / or the current and / or the electrical resistance between the two electrodes of a pair of electrodes in

Dependence on time measured.

The method of the invention has the advantage of allowing detection of the size distribution of particles in a gas stream in both a constant velocity gas stream and a variable velocity gas stream. When a gas flow is at a constant rate, the voltage (s) at the electrode pairs of the electrode system are preferably applied constant.

However, for gas streams of variable gas velocity, the attachment of each size fraction may shift from one pair of electrodes to an adjacent pair of electrodes.

Therefore, if there is a gas flow at a variable speed, the measurement can be performed with voltages applied constantly to the electrode pairs, and the change in gas velocity can be included as a correction factor in the evaluation, or the voltages applied to the electrode pairs of the electrode system, in particular directly, adapted to the change in gas velocity.

In this case, the adaptation of the voltages applied to the electrode pairs of the electrode system has the advantage that a displacement of the size fractions is avoided.

Another object of the present invention is the use of a sensor according to the invention and / or a method according to the invention in a workshop measuring device for emission analysis or in a measuring device for controlling the air quality or in soot-particle sensors, in particular soot-particle sensors for "on board diagnosis "(OBD), and / or to monitor the operation of a

Internal combustion engine, such as a diesel engine, or an incinerator, such as an oil heater or a furnace, and / or to monitor the functioning of a particulate filter and / or monitoring the load condition of a particulate filter, such as a diesel particulate filter (DPF), or for monitoring of chemical manufacturing processes, exhaust air systems and / or exhaust aftertreatment systems.

Claims

claims

A sensor for detecting the size distribution of particles in a gas stream, comprising

an electrode system having at least three electrodes (1, 1 ', 2', 2 ', 3', 3 ', 4', 4 ') lying in one plane,

at least one power supply device (201; 202; 203; 204) and

at least one voltage measuring and / or current measuring device (301, 302, 303, 304), characterized in that

two electrodes of different polarity (1, 1 ', 2', 2 ', 3', 3 ', 4, 4') in the electrode system form a pair of electrodes (11, 12, 13, 14), the pairs of electrodes (11; 13, 14) are arranged along a notional jet (X1, S1) lying in the plane of the electrodes in such a way that the beam (X1, S1) is connected between the two electrodes (1, 1 ', 2, 2', 3) , 3 ', 4, 4') of an electrode pair (11, 12, 13, 14),

- Wherein the along the beam (Xl; Sl) arranged electrode pairs (11; 12; 13; 14) are connected to at least one voltage measuring and / or current measuring device (301; 302; 303; 304) that the voltage and / or of the

Current flow between each pair of electrodes (11, 12, 13, 14) can be determined individually.

2. Sensor according to claim 1, characterized in that - each along the beam (Xl; Sl) arranged electrode pair (11; 12; 13; 14) to its own voltage measuring and / or current measuring device (301; 302; 303; 304) connected; and or

- A plurality along the beam (Xl; Sl) arranged electrode pairs (11; 12; 13; 14) are connected via a switch to a common voltage measuring and / or current measuring device, wherein the switch between the individual electrode pairs (11; 12; 13; 14) is switched to determine the voltage and / or the current flow of each individual electrode pair (11; 12; 13; 14).

3. Sensor according to claim 1 or 2, characterized in that the electrode system at least two lying in the plane of the electrodes beams (Xl; X2; X3; Sl; S2; S3; S4; S5; S6; S7; S8) which extend radially from a common point P and along which pairs of electrodes (11, 12, 13, 14 to 81, 82, 83, 84) are arranged in such a way that the respective beam is connected between the two electrodes (1 , 1 'to 4g, 4g') of the electrode pairs (11, 12, 13, 14 to 81, 82, 83, 84) arranged on it.

4. Sensor according to claim 3, characterized in that the at least two beams (X1; X2; X3; X4; Sl; S2; S3; S4; S5; S6; S7; S8) extend radially from the common point P in such a way in that all adjacent beams (X1; X2; X3; X4; Sl; S2; S3; S4; S5; S6; S7; S8) enclose approximately the same angle.

5. Sensor according to claim 3 or 4, characterized in that the at least two beams lying in the plane of the electrodes (X1; X2; X3; X4; Sl; S2; S3; S4; S5; S6; S7; S8) of extend radially outward from a common point P such that the electrodes arranged thereon extend over two cutouts (2001, 2002) of a substantially round surface, with electrode-free partial surfaces (3001, 3002) lying between these cutouts.

6. Sensor according to one of claims 3 to 5, characterized in that those

Electrode pairs (11 to 81, 12 to 82, 13 to 83, 14 to 84), which on the respective beams (Sl; S2; S3; S4; S5; S6; S7; S8) the first, second, ... or n-th electrode pairs are each substantially the same configuration and / or the same distance with respect to the point P, wherein the numbering of the electrode pairs (11 to 81, 12 to 82, 13 to 83, 14 to 84) starting from the point P. radially outward takes place.

7. Sensor according to one of claims 3 to 6, characterized in that those electrode pairs (11 to 81, 12 to 82, 13 to 83, 14 to 84), on the respective beams, the first, second, ... or n Each pair of electrodes are connected to a common voltage measuring and / or current measuring device (301, 302, 303, 304) and / or power supply device (201, 202, 203, 204), wherein the numbering of the electrode pairs (11 to 81; 12 to 82, 13 to 83, 14 to 84) starting radially from the point P.

8. Sensor according to one of the preceding claims, characterized in that in each case the two electrodes (1, 1 'to 4g, 4g') arranged along one of a beam (Sl; S2; S3; S4; S5; S6; S7; S8) Electrode pair (11 to 84) are formed and / or arranged substantially mirror-symmetrical to each other, wherein the extending between the two electrodes of a pair of electrodes beam (S 1, S2;

S3; S4; S5; S6; S7; S8) forms the mirror axis.

9. Sensor according to claim 1 to 5, characterized in that two or more arranged on one side of a beam (Xl; X2; X3; X4) electrodes are formed as an electrode (1; Ia; Ib; Ic), wherein the the other side of the

Beam (X1; X2; X3; X4) arranged electrodes (1 ', 2', 3 ', 4'; 1a ', 2a', 3a ', 4a'; 1b ', 2b', 3b ', 4b'; ', 2c', 3c ', 4c') are spaced apart from one another and have a different polarity than the electrode (1; 1a; 1b; 1c) arranged on one side of the beam (X1; X2; X3; X4) and with the electrode (1; 1a, 1b; 1c) arranged on one side of the beam (X1; X2; X3; X4) in each case has an electrode pair (11;

12; 13; 14), wherein the electrode pairs (11; 12; 13; 14) arranged along the beam (Xl; Sl) are connected to at least one voltage measuring and / or current measuring device (301; 302; 303; 304) such that the voltage and / or the flow of current between each electrode pair (11; 12; 13; 14) can be determined individually.

10. Sensor according to one of the preceding claims, characterized in that along a beam (Xl; Sl) at least three pairs of electrodes (11; 12; 13; 14) are arranged.

11. Sensor according to one of the preceding claims, characterized in that the electrode pair gap distance A in each pair of electrodes (11; 12; 13; 14; 15; 16; 17) is designed such that, given the expected particle size distribution, all electrode pairs (11; 12 ; 13; 14; 15; 16; 17) provide and / or regenerate measurement results in the same time range.

12. Sensor according to one of the preceding claims, characterized in that the electrode widths B and / or electrode lengths D and / or the distances between the electrode pairs C are adapted to the expected particle size distribution and / or flow rate.

13. Sensor according to one of the preceding claims, characterized in that

- Two or more pairs of electrodes (11; 12; 13; 14) are each connected to a separate power supply device (201; 202; 203; 204); and / or - two or more electrode pairs (11; 12; 13; 14) to a common one

Power supply device (201) are connected, wherein the pairs of electrodes (11; 12; 13; 14) each have their own series resistor (401; 402; 403; 404) for setting an individual voltage.

14. Sensor according to one of the preceding claims, characterized in that each

Adjacent electrode pair (1001; 1002; 1003; 1001 '; 1002'; 1003 ') is connected to at least one voltage measuring and / or current measuring device (501; 501'; 502; 502 '; 503; 503') such that the voltage and / or the current flow between each neighboring electrode pair (1001; 1002; 1003; 1001 '; 1002'; 1003 ') can be determined individually, wherein a neighboring electrode pair (1001; 1002;

1003; 1001 '; 1002 '; 1003 ') comprises a pair of two adjacent electrodes (1, 2, 3, 4) arranged on the same side of a beam (X1; X2; X3; X4; Sl; S2; S3; S4; S5; S6; S7; S8) 1 ', 2', 3 ', 4') of different polarity.

15. A method for detecting the size distribution of particles in a gas stream with a sensor according to one of claims 1 to 14, by

a voltage is applied to the electrode pairs (11; 12; 13; 14 to 81; 82; 83; 84) of the electrode system or to the electrode pairs (11; 12; 13; 14 to 81; 82; 83; 84) of the electrode system each independent voltages are applied, whereby accumulate particles,

the change in voltage and / or current and / or the electrical resistance between the two electrodes of a pair of electrodes (11; 12; 13; 14 to 81; 82; 83; 84) resulting from the particle deposition, is applied to each pair of electrodes (11; 12 ; 13; 14 to 81; 82; 83; 84) individually and - the size distribution of the particles and / or the particle concentration and / or the particle mass flow by evaluating the changes in the voltage and / or the current and / or the electrical resistance of the respective electrode pairs (11; 12; 13; 14 to 81; 82; 83; 84).

16. The method according to claim 15, characterized in that each of the

Electrode pairs (11; 12; 13; 14 to 81; 82; 83; 84) applied voltages such are set that deliver all the electrode pairs in the same time range measurement results and / or regenerated in the expected particle size distribution.

17. The method according to claim 15 or 16, characterized in that

if there is a gas flow at a constant speed, the voltage / s at the electrode pairs (11; 12; 13; 14 to 81; 82; 83; 84) of the electrode system is / are constantly applied or

if there is a gas flow with a variable speed, the measurement is made with constant at the electrode pairs (11; 12; 13; 14 to 81; 82;

83; 84) applied voltages and the change of the

Gas velocity is included as a correction factor in the evaluation or

the voltages applied to the pairs of electrodes (11; 12; 13; 14 to 81; 82; 83; 84) of the electrode system correspond to the change in the

Gas speed can be adjusted.

18. Use of a sensor according to any one of claims 1 to 14 and / or a method according to any one of claims 15 to 17 in a workshop measuring device for emission analysis or in a measuring device for controlling the air quality or in soot-particle sensors and / or for monitoring the mode of operation of an internal combustion engine or an incinerator and / or for monitoring the functionality of a particulate filter and / or for monitoring the loading state of a particulate filter or for monitoring of chemical manufacturing processes, exhaust air systems and / or

Exhaust after-treatment systems.