Sensor device with capacitive sensor

Abstract

A sensor device (1) comprising a first electrode (2), a signal generating device (22) for applying an electrical signal (S) to the first electrode (2), whereby the first electrode (2) outputs an electric field (E1), and a second electrode (4) spaced apart from the first electrode (2) for recording the electric field output by the first electrode, to which a measured value M1 belongs. According to the present invention, the sensor device (1) comprises a third electrode (6) and a signal generating device (62) for applying a second electrical signal (S2) to the other electrode (6), whereby the other electrode (6) outputs another electric field (E2), to which a measured value M2 belongs.

Description

Technical Field

[0001] The present invention relates to a sensor device and in particular to a sensor device having a capacitive sensor. Capacitive sensors are used in various ways to detect dielectric objects and conductive objects in the close range of an electric field. The capacitive action principle is particularly well suited for detecting people and living beings. Object detection can be used to implement comfort functions, for example in the case of touch-sensitive displays, or also to implement safety functions, for example for human-machine collaboration. Background Art

[0002] Other applications are, for example, level sensors and proximity switches which can be used in process control.

[0003] Capacitive sensor systems enable contactless safety functions that initiate a safe state even before a force action occurs on an object in the danger zone. To this end, the sensor must have a sufficiently large detection range to be able to take into account reaction and delay times.

[0004] For reliable detection of objects, suitable capacitive sensor systems are those which operate according to the principle of projected mutual capacitance and consist of electrode pairs, in which one electrode usually extends or outputs a variable electric field and the induced displacement current is measured with the aid of the second electrode in the field. Capacitive sensor systems of this type can also detect environmental influences such as air humidity and splashing water in the immediate vicinity of the sensor.

[0005] In addition, temperature-induced expansions and compressions, in particular expansions and compressions of mechanical components in the close proximity of the sensor, and temperature dependencies in the properties of the circuit components used may also have an influence. For robust proximity detection, these influences must be avoided by limiting the application or by additional devices, or compensated by suitable measures.

[0006] For this reason, capacitive sensors are hardly ubiquitous, particularly in outdoor areas and / or where environmental conditions change rapidly, such as in the case of use in motor vehicles.

[0007] DE 10 2016 217 545 A1 discloses the use of an electrode arrangement and a device for interrupting a water film in front of a capacitive sensor, wherein the sensor function is maintained even when a water film forms in front of the sensor, for example in outdoor areas.

[0008] A dual sensor system is known from US 939 0061 B, in which a movable sensor is responsible for object recognition and an immovable sensor is used to recognize environmental influences. The invention is based on the following object: to achieve recognition and compensation of environmental influences on approach recognition. A purely capacitive sensor should be used here, which particularly preferably operates according to the mutual capacitance principle. Summary of the invention

[0009] This object is achieved according to the invention by a device and a method according to the independent claims. Advantageous embodiments and developments are the subject matter of the dependent claims.

[0010] The sensor device according to the invention, in particular a capacitive sensor device, has a first electrode and a signal generating device that applies an electrical signal to the first electrode, thereby causing the first electrode to output an electric field. The sensor device also has a second electrode that is spaced apart from the first electrode and is suitable and designed to record the electric field output by the first electrode.

[0011] According to the present invention, the sensor device has a third electrode and a signal generating device for applying a second electric signal to the third electrode, thereby causing the third electrode to output a further electric field.

[0012] A first measurement value (hereinafter referred to as M1) may correspond to or belong to the electric field output by the first electrode. A second measurement value (hereinafter referred to as M2) may correspond to or belong to the electric field output by the third electrode.

[0013] It is therefore proposed to use, in addition to the two electrodes conventionally used, further electrodes, which are described below and are used in particular for detecting elements or disturbances in the near-field region. The sensor device is therefore preferably expanded with one or two or more additional electrodes, also referred to below as compensation electrodes, which are particularly preferably arranged close to the existing electrodes and particularly preferably enable the detection of changes specifically in the near-field region of the sensor or its electrodes and preferably also in the properties of the measuring circuit and the oscillator circuit. This is preferably independent of the influence of objects in the far-field region.

[0014] In a preferred embodiment, the first electrode and the second electrode are arranged in a common plane. In another preferred embodiment, the first and second electrodes are arranged offset from each other along a direction extending in the plane of at least one of the two electrodes. Therefore, preferably, the two electrodes are not arranged opposite to each other (for example, in the case of a capacitor).

[0015] The sensor according to the invention is therefore able to compensate for influences caused by objects, for example water drops in the form of droplets or flowing out in grooves, water spray or rain, in particular as long as there is no closed water film between the two electrodes mentioned above.

[0016] In a first preferred embodiment, the first electrode is an emitting electrode that outputs the electric field. The electric field is preferably an electrostatic alternating field. The second electrode is preferably a measuring electrode that detects and / or measures the field output by the sensor electrode, in particular the electric field.

[0017] Preferably, the third electrode is a further transmitting electrode, which likewise outputs an electric field. In this case, the electric field can in particular be detected by the second electrode.

[0018] In a further preferred embodiment, the sensor device has an amplifier device and in particular a signal amplifier which converts the displacement current at the second electrode or the measuring electrode as undistorted as possible into a measurement signal and in particular into an evaluable and transmittable measurement signal.

[0019] In a further preferred embodiment, the sensor device has an evaluation device which processes the measurement signal. In this case, the evaluation device can preferably also return the measured value in order to signal approach detection, if necessary.

[0020] In a further preferred embodiment, the device also has a control device, which is described in more detail below, and which manages the operating mode mentioned here, ie, detects the signal output by the first electrode and also detects the signal output by the third electrode.

[0021] In another preferred embodiment, a circuit, in particular an oscillator circuit, is provided, which outputs a predetermined signal, in particular a periodic signal. Here, the signal can be rectangular, triangular, sawtooth or sinusoidal, for example. Preferably, the signal has a sufficiently large voltage amplitude and also indicates the driver capability.

[0022] In a preferred embodiment, parameters of the signal, such as signal shape, frequency and / or amplitude, can be changed. In this case, in particular, these parameters can also be dynamically adapted.

[0023] In another preferred embodiment, the sensor device is designed as a proximity sensor device and is particularly suitable and intended for detecting objects in the environment of the sensor device. The environment of the sensor device is understood to be a region at a distance of less than 1 m, preferably less than 80 cm, preferably less than 60 cm, particularly preferably less than 50 cm from the electrode.

[0024] In another preferred embodiment, the first and / or second electrode is suitable and intended for recording the electric field output by the third electrode. Particularly preferably, the second electrode is suitable and intended for recording the electric field. Thus, a field can also be caused or a displacement current can be generated in the second electrode by the third electrode. This displacement current can again be determined.

[0025] In another advantageous embodiment, the sensor device has a water film prevention device, which is suitable and designed to prevent a water film extending between two electrode films and / or to destroy such a water film. Here, the device can be designed, for example, as a protrusion arranged between the two electrodes. Preferably, the protrusion is made of a non-conductive material. Here, the protrusion can extend, for example, perpendicularly to a geometric connecting line extending from one electrode to the other electrode.

[0026] In a further advantageous embodiment, the device has a control device which causes the first signal to be applied to the first electrode during a first predefined time period and the second signal to be applied to the third electrode during a second predefined time period.

[0027] Particularly preferably, these time periods are separated from one another and preferably completely separated from one another. Thus, it is particularly preferred that the first signal and the second signal are not output simultaneously. Particularly preferably, the two signals are output alternately and / or cyclically. It is possible here to output the first signal in a predefined first time period and then to output the second signal in a second time period. Particularly preferably, the time period in which the second signal is output is shorter than the time period in which the first signal is output.

[0028] In this way, the situation is taken into account that the device is usually used as a detection device or sensor device in normal use and data characterizing environmental influences are determined only temporarily, in part for calibration purposes, with the aid of the third electrode.

[0029] Here, the electrical signals may be the same, that is, the same electrical signal is applied to the first electrode and the third electrode. However, the signals applied to the first electrode may also be different from those applied to the third electrode.

[0030] In general, an oscillator signal is applied to the transmitting electrode and the third electrode, which is also referred to below as the combination electrode, and particularly preferably the oscillator signal is applied alternately to the transmitting electrode and the third electrode, which is also referred to below as the combination electrode. In this way, independent measured values ​​M1 and M2 are obtained for the two operating modes "actuating the first electrode" (M1) and "actuating the third electrode" (M2). The oscillator signals for the two operating modes can be different.

[0031] In another preferred embodiment, in the operating mode (first electrode switched on), the first electrode stretches an electric field which preferably extends further into the space and is changed by objects in the long-range region of the sensor. However, changes in the short-range region of the sensor and temperature-induced expansions of objects, such as water drops, running water or mechanical covering parts, also have a measurable influence on the field stretched by the first electrode. Such changes therefore act in a parasitic manner. Changes in the properties of the measuring amplifier circuit and the evaluation device can also influence the measured values ​​using the manipulated first electrode.

[0032] The third electrode or compensation electrode is preferably designed such that in the operating mode "compensation electrode actuated", as described below, it extends a spatially concentrated field in the close range of the measuring electrode. The measured values ​​with the actuated third electrode are therefore primarily influenced by changes in the close range of the measuring electrode and in the properties of the measuring amplifier circuit and the evaluation device.

[0033] As a result, precisely those influences which have to be compensated for long-range area detection are detected by actuating the third electrode.

[0034] In another preferred embodiment, the third electrode is closer to the second electrode than the first electrode. The third electrode can therefore be integrated into the second electrode, for example in an electrically or galvanically isolated manner. In this way, the second electrode can detect the near field of the third electrode.

[0035] Particularly preferably, the third electrode outputs an electric field having a smaller range than the first electrode. Therefore, the third electrode is particularly preferably used for detecting objects in the close range, in particular in the close range of the second electrode.

[0036] In another preferred embodiment, at least one electrode can also function as both a transmitting electrode and a measuring electrode. Thus, by corresponding control, for example, the first electrode can function partially as a transmitting electrode and partially as a measuring electrode. The second electrode can also sometimes function as a transmitting electrode and sometimes as a measuring electrode.

[0037] It is also conceivable that physically only two electrodes are present, but that one electrode assumes the function of two electrodes by control. In this case, the electrodes are provided by corresponding control on the control side. However, as mentioned above, preferably three electrodes are physically present or particularly preferably three electrodes that are electrically and / or galvanically isolated from each other.

[0038] In another advantageous embodiment, the electrode area of ​​the third electrode is smaller than the electrode area of ​​the first electrode and / or smaller than the electrode area of ​​the second electrode.

[0039] In another preferred embodiment, the third electrode is at least partially and particularly preferably completely surrounded by the second electrode. Preferably, the third electrode is arranged in a plane spanned by the second electrode.

[0040] In another preferred embodiment, the sensor device has an evaluation device, which evaluates the signal recorded by the second electrode and / or evaluates the signal output from the second electrode due to the induction. As mentioned above, this can especially be the induced signal and / or the induced displacement current or the like.

[0041] In another preferred embodiment, the sensor device has a fourth electrode. Therefore, the sensor device can have a first compensation electrode and a second compensation electrode (the fourth electrode).

[0042] In this case, the fourth electrode can be placed close to the first electrode. The fourth electrode or the second compensation electrode can preferably be connected as a second measuring electrode and can record further measured values, in particular in an operating mode in which the transmitting electrode or the first electrode is actuated.

[0043] Particularly preferably, the fourth electrode or the second compensation electrode is designed and arranged in such a way that the field between the transmitting electrode and the compensation electrode is spatially concentrated in a close proximity region of the transmitting electrode.

[0044] The present invention also focuses on a method for operating a capacitive sensor device, wherein a signal generating device applies a current to a first electrode and / or supplies an electrical signal to the first electrode, thereby causing the first electrode to output an electric field, wherein the electric field output from the first electrode is recorded using a second electrode spaced apart from the first electrode.

[0045] According to the invention, the sensor device has a third electrode and a signal generating device, wherein a further electric field is emitted by the third electrode. Particularly preferably, the electric field emitted by the third electrode is also detected by the second electrode. Therefore, the third electrode preferably also acts as a transmitting electrode.

[0046] In a preferred method, an electrical signal is sometimes applied to the first electrode and sometimes to the third electrode. Particularly preferably, these time periods differ from one another, so that particularly preferably the electric field or the electrical signal is not applied to both the first electrode and the third electrode at any time.

[0047] In a further preferred method, a first measured value is determined by means of an evaluation device, and a second measured value is also determined, and a compensated measured value is determined based on the first measured value and the second measured value, wherein the first measured value depends on the electric field output by the first electrode and recorded by the second electrode, and the second measured value depends on the field output by the third electrode and recorded by at least one electrode and in particular by the second electrode. Mathematical methods, in particular proportionality methods, can be used for the determination.

[0048] The invention thus enables robust approach detection by means of a capacitive sensor system even under changing environmental influences due to the internal compensation. Specifically, the invention can be suitable, for example, for environmental monitoring when driving, maneuvering and parking a vehicle, in particular also in indoor and outdoor areas.

[0049] Preferably, in order to realize a robust and safe sensor system, the present invention can be combined with a parallel invention of a capacitive three-electrode sensor for safe long-range detection and a capacitive sensor system positioned independently of the environment, wherein the three-electrode sensor proposed here can also be expanded to a four-electrode sensor, a five-electrode sensor or a six-electrode sensor.

[0050] The invention provides a high degree of robustness of approach detection under environmental influences, ie even in the event of rain, temperature fluctuations or deformation of the mechanical cover in the sensor region, for example. Functional advantages are achieved in this way.

[0051] Furthermore, no special sensor system is required for detecting environmental influences, and no or only a small additional space is required for compensation electrodes in existing capacitive sensor systems. Advantages in terms of integration and costs are achieved in this way.

[0052] As mentioned above, it is particularly preferred that the third electrode or compensation electrode is small or occupies a small area compared to the transmitting electrode.It is particularly preferred that the compensation electrode also has a small distance from the measuring electrode.

[0053] Furthermore, in order to be able to compensate for mechanical obstacles, water droplets, and running water, in particular in the close range of the sensor device, it is advantageous in all arrangements if the compensation electrode can act freely in the direction of the spatial region in which the electric field between the first electrode and the second electrode exists.

[0054] Preferably, the evaluation device uses the predetermined measured values ​​of the different operating modes, ie the normal measurement and the measurement in the close-range area, to mathematically perform compensation and return compensated measured values ​​for long-range detection. In a preferred method, a possible compensation method is proposed.

[0055] On the one hand, a ratiometric method can be used. Here, the initial value Mi of the sensor is known, which is recorded in an operating mode with a controlled combined electrode without an object influencing the reference temperature and the reference humidity. The compensated measured value is calculated by the ratiometric method:

[0056] M kompensiert =M1*Mi / M2.

[0057] In another preferred method, a two-dimensional look-up table (LUT) can be used. In this case, the sensor device is first calibrated. For this purpose, in a first calibration step, reference objects can be placed at different defined positions in the remote area of ​​the sensor device (in particular at a reference temperature and a reference humidity).

[0058] The measured values ​​M1 and M2 from the calibration are then preferably plotted in a table, in particular in an at least two-dimensional table along both dimensions. The reference measured values ​​M1 from the calibration are each filled in with the corresponding compensated measured values ​​M2. kompensiert The cell contents.

[0059] In a further calibration step, reference objects are likewise placed at different defined positions in the long-range region of the sensor.

[0060] In addition, the sensor arrangement is then exposed to influences to be compensated, such as splashing water, changes in temperature and air humidity or mechanical changes in the close range of the sensor. The value table is further filled, wherein in the cell for each measured value pair (M1 / M2) instead of the current measured value M1, the reference value from the first calibration step, which is matched to the object position, is now entered.

[0061] Preferably, the table of values ​​generated during the calibration is stored as a LUT and in particular in the above-mentioned evaluation device.

[0062] In actual long-range detection, the table section at the location of the updated or current measured values ​​M1 and M2 is looked up and / or preferably interpolated by interpolation of reference values ​​from adjacent zones and used as compensated measured value M kompensiert return.

[0063] In another possible method, a model function is applied. In this case, a mathematical function can be used to map the lookup table (see above). Additionally or alternatively, some sampling points from the calibration can also be used to set the model parameters in particular.

[0064] By using the current measured value in the model function, the compensated measured value can be determined. kompensiert =f(M1,M2).

[0065] Of the three methods mentioned, the above-described proportional method has the advantage of requiring the lowest memory and computing power, but still provides at least robust or accurate results. The described method using a lookup table provides very good results with a corresponding quality of the calibration data, but is accompanied by an increased memory requirement. The method using the above-described model function allows a system-specific compromise between robustness, memory requirement and computing effort.

[0066] It is also conceivable to use an artificial neural network as a model function and / or to create a model function. In this case, the adaptation or training can be performed in particular by machine learning.

[0067] In this case, the measured values ​​(hereinafter referred to as M1 and M2) can be used as input values, respectively, or training data can be used, which can be reference values ​​from calibration under different environmental conditions and / or at the corresponding positions of reference objects. As output values, compensated measured values ​​M kompensiert .

[0068] Additionally, dynamic training during operation and / or dynamic training during runtime is also conceivable.

[0069] Preferably, the sensor device is operated using one or more mathematical methods which convert the compensated measured value M kompensiert Assigned to the measured values ​​M1 and M2. In this case, the compensated measured values ​​and / or the measured values ​​M1 and M2 can be adjusted by calibration or training. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Further advantages and embodiments emerge from the drawings.

[0071] In it:

[0072] Figure 1A sensor device according to the prior art is shown;

[0073] Figure 2 shows a schematic diagram of a sensor device according to the present invention;

[0074] Figure 3 Shows the calibration status Figure 2 Sensor device;

[0075] Figure 4 A diagram of a lookup table is shown;

[0076] Figure 5 A diagram showing a function for evaluating measurement results;

[0077] Figure 6 shows a schematic diagram according to another embodiment of the present invention;

[0078] Figure 7 Another schematic diagram according to an embodiment of the present invention is shown;

[0079] Figure 8 A further schematic diagram of an embodiment of a sensor device according to the invention is shown. DETAILED DESCRIPTION

[0080] Figure 1 A schematic diagram of a sensor device 100 according to the prior art is shown. The sensor device 100 has a first electrode 2 and a second electrode 4. These electrodes are arranged on a common carrier 15. Reference numeral 22 denotes a signal generating device which outputs a signal S to the first electrode 2. The signal generates an electric field E. This electric field E is partially recorded by the second electrode 4 and in this way induces a displacement current (Verschiebestrom) which can be measured accordingly. In this case, for example, objects located in the area between the electrode 2 or the electrode 4 also influence the electric field, and objects located in the remote area between the two electrodes 2 and 4 also influence the electric field.

[0081] However, objects or disturbances such as water films, dirt etc. can also influence the measurement.

[0082] Figure 2 A sensor device 1 according to the invention is schematically shown. The sensor device also has a first electrode 2 and a second electrode 4. Here, a signal S1 is applied to the first electrode 2 via a signal generating device 22 and an electric field E1 is generated in this way. This electric field E1 is recorded by the second electrode 4, which generates a displacement current V1, which in turn can be measured by means of a measuring device.

[0083] Accordingly, the displacement current or a signal corresponding to the displacement current can be output as a first measurement signal via the evaluation device 10. The evaluation device 10 therefore advantageously calculates the first measurement signal M1 from the displacement current.

[0084] The two electrodes 2 and 4 are here designed in a plate-like manner and are preferably parallel to each other, so that the electric field lines not only extend in a straight direction between the electrodes 2, 4, but also have Figure 2 In this way, objects can also be recorded in the remote region of the two electrodes 2 , 4 , even though this remote region is not arranged or located geometrically between the electrodes 2 , 4 .

[0085] The electrodes are preferably arranged on a common carrier. Furthermore, the signal generating device(s) may also be arranged on the carrier.

[0086] Reference numeral 6 denotes a third electrode, which is arranged here in the region of the second electrode 4. Figure 2 In the state shown in , no signal is supplied to the third electrode 6. However, here too, a signal generating device 62 is provided, which can apply, in particular, an electrical signal to the third electrode 6.

[0087] Reference numeral 8 denotes a control device which, using a signal, causes the first electrode 2 and the third electrode 6 to be actuated. In this case, the control device can, for example, actuate the two signal generating devices 22 and 62 in different time periods. However, it should be noted that the control device 8 and the two signal generating devices 22 and 62 can also be accommodated in a common control unit.

[0088] Figure 3 Shows Figure 2 A diagram of a sensor device 1 is shown in FIG. Figure 3 In the situation shown in , the signal is no longer applied to the first electrode 2, but to the third electrode 6. The third electrode 6 also outputs the electric field E2, but only or especially in the close range, so that this electric field is also only recorded by the second electrode 4 here. In particular, disturbances in the close range of the second electrode 4 also have an effect on the electric field E2. The measurement signal of the third electrode 6 or the signal output by the third electrode 6 can be used to detect disturbances in the close range of the sensor device or to calibrate the values ​​accordingly.

[0089] In response to the field E2, a displacement current can be output to the evaluation device 10, which calculates the second measurement signal M2 from the displacement current. Furthermore, the evaluation device or processor device (not shown) can determine a compensated signal M from the first measurement signal M1 and the second measurement signal M2. kompensiert .

[0090] Figure 4 An example of a two-dimensional lookup table is shown. Here, the measured values ​​M1 are plotted on the ordinate and the measured values ​​M2 are plotted on the abscissa. The cells contain the individual compensated measured values ​​M kompensiert When using this LUT (look up table), a compensated measured value can be determined in each case when different measured values ​​M2 and M1 occur, or a compensated measured value can be determined, for example, by interpolation or averaging.

[0091] Figure 5 A graphical representation within the scope of another measuring method is shown. A quadratic model function is shown here, which is plotted on a two-dimensional value table. The boundary conditions are represented by the reference symbol R. However, as mentioned above, the model parameters can also be specified with the aid of other sampling points from the calibration.

[0092] Apart from Figure 2 In addition to the arrangements of other electrodes shown in , other arrangements of these electrodes are also contemplated.

[0093] So for example Figure 6 An example is shown in which the third electrode 6 surrounds the second electrode or measuring electrode. Figure 7 Configurations are shown in which the third electrode is arranged laterally next to the second electrode or measuring electrode. However, all these arrangements have in common that the third electrode occupies a smaller area than the transmitting electrode or first electrode 1 and is at a smaller distance from the measuring electrode 4.

[0094] In order to be able to compensate for water drops, running water and mechanical changes in the close range of the sensor device in all arrangements, it is also advantageous if the third electrode or compensation electrode can act freely in the direction of the spatial region in which the electric field between the transmitting electrode and the measuring electrode exists. The reference symbol E2 respectively denotes a field line when measuring the electric field output by the third electrode. Figure 6 and Figure 7 In the situation shown in , the third electrode is respectively activated and therefore an operating mode compensation for environmental influences occurs with the third electrode as an active transmitting electrode.

[0095] Figure 8 Another embodiment of the sensor device according to the invention is shown. In this embodiment, the sensor device has two compensation electrodes. Here, the sensor device with compensation electrode 6 is expanded with a second compensation electrode 16 or fourth electrode 16. This electrode is placed near the first electrode 2, here for example inside the first electrode 2.

[0096] The electrode 16 is preferably connected as a second measuring electrode and preferably records the measured value M3 in the operating mode of "controlling electrode 2". In this case, the fourth electrode 16 is designed and arranged so that the field between the first electrode or transmitting electrode 2 and the fourth electrode 16 is spatially concentrated in the close range of the transmitting electrode, that is, the close range of the first electrode 2.

[0097] Except in Figure 8 In addition to the configuration shown in , other configurations are also possible, in particular, for example with Figure 6 and Figure 7 A combination of the configurations shown in .

[0098] Therefore, in Figure 8 In the embodiment shown, two further electrodes or compensation electrodes 6 , 16 are preferably provided in addition to the first and second electrodes, which in this way enable close-range detection both in the region of the first electrode and in the region of the second electrode.

[0099] The applicant reserves the right to claim all features disclosed in the application documents as being essential to the invention, provided that these features are new with respect to the prior art either individually or in combination. It should also be noted that features which may be advantageous in themselves are also described in the various drawings. It is immediately apparent to a person skilled in the art that a particular feature described in a drawing may be advantageous even without the use of other features in the drawing. It is also apparent to a person skilled in the art that advantages may also be obtained by combining a plurality of features shown in the various drawings or in different drawings.

[0100] Reference numerals list

[0101] 1 Sensor device

[0102] 2. First electrode

[0103] 4 Second electrode

[0104] 6 Third electrode

[0105] 8 Control device

[0106] 10 Evaluation Device

[0107] 15 Carrier

[0108] 16 Compensation electrode, fourth electrode

[0109] 18, 22, 62 Signal generating device

[0110] 100 Sensor device (prior art)

[0111] E, E1, E2 Electric field

[0112] M1, M2, M3 measurement values

[0113] M kompensiert Compensated measured value

[0114] E Field Lines

[0115] R Boundary Conditions

[0116] S, S1, S2, S3 (electrical) signal

[0117] V1 displacement current.

Claims

1. A sensor device (1), comprising: A first electrode (2) having a first signal generating device (22) for applying a first electric signal (S1) to the first electrode (2), thereby causing the first electrode (2) to output an electric field (E1); a second electrode (4), the second electrode being spaced apart from the first electrode (2) and being used for recording the electric field output by the first electrode in a near-range area and a far-range area of ​​the second electrode (4); a third electrode (6) having a second signal generating device (62) for applying a second electric signal (S2) to the third electrode (6), thereby causing the third electrode (6) to output a further electric field (E2) in a close proximity region of the second electrode for recording by the second electrode (4); and An evaluation device, characterized in that The evaluation device is configured to: determining a first measurement value, the first measurement value being dependent on the electric field (E1) output by the first electrode (2) and recorded by the second electrode (4); determining a second measurement value, the second measurement value being dependent on the field (E2) output by the third electrode (6) and recorded by the second electrode (4); and A compensated measurement value is determined based on the first measurement value and the second measurement value.

2. The sensor device (1) according to claim 1, characterized in that The sensor device (1) has a control device (8) which causes a first electrical signal (S1) to be applied to the first electrode (2) during a first predetermined period of time and a second electrical signal (S2) to be applied to the third electrode (6) during a second predetermined period of time.

3. The sensor device (1) according to claim 1 or 2, characterized in that The third electrode (6) is arranged closer to the second electrode (4) than the first electrode (2).

4. The sensor device (1) according to claim 1 or 2, characterized in that The electrode area of ​​the third electrode (6) is smaller than the electrode area of ​​the first electrode (2) and / or smaller than the electrode area of ​​the second electrode (4).

5. The sensor device (1) according to claim 1 or 2, characterized in that The evaluation device evaluates the signal recorded by the second electrode.

6. The sensor device (1) according to claim 1 or 2, characterized in that The sensor device (1) has a fourth electrode (16) which is arranged close to the first electrode as an additional compensation electrode.

7. A method for operating a capacitive sensor device, wherein a first signal generating device (22) applies a first electrical signal (S1) to a first electrode (2), thereby causing the first electrode (2) to output an electric field (E1), and wherein the electric field (E1) output by the first electrode (2) is recorded in a close range and a long range of the second electrode (4) by means of a second electrode (4) spaced apart from the first electrode (2), It is characterized in that The sensor device (1) comprises a third electrode (6) and a second signal generating device (62) for applying a second electrical signal (S2) to the third electrode (6), whereby the third electrode (6) outputs a further electric field (E2), wherein a first measured value (M1) is determined by means of an evaluation device, and a second measured value (M2) is also determined, and a compensated measured value (M2) is determined based on the first measured value (M1) and the second measured value (M2). kompensiert ), wherein the first measurement value depends on the electric field output by the first electrode and recorded by the second electrode (4), and the second measurement value depends on the electric field output by the third electrode and recorded by the second electrode (4).

8. The method according to claim 7, characterized in that An electric signal is sometimes applied to the first electrode (2) and sometimes applied to the third electrode (6).

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