Sensor device with capacitive sensor

Abstract

A sensor device includes a first electrode and a first signal generation device configured to apply an electrical signal to the first electrode such that the first electrode emits a first electrical field. The sensor device further includes a second electrode located at a first distance from the first electrode and configured to pick up the first electrical field. A third electrode and a second signal generation device configured to apply an electrical signal to the third electrode such that the third electrode emits a second electrical field is included in the sensor device.

Claims

1. A sensor device, comprising: a first electrode; a first signal generation device configured to apply an electrical signal to the first electrode such that the first electrode emits a first electrical field; a second electrode located at a first distance from the first electrode and configured to pick up the first electrical field; a third electrode; a second signal generation device configured to apply an electrical signal to the third electrode such that the third electrode emits a second electrical field which is picked up by the second electrode; and an evaluation device configured to determine a first measured value, the first measured value depending on the emitted first electrical field picked up by the second electrode; determine a second measured value, the second measured value depending on the emitted second electrical field picked up by the second electrode; and determine a compensated-for measured value using the first measured value and the second measured value.

2. The sensor device according to claim 1, further comprising: a control device configured to cause the first signal to be applied to the first electrode at first set time intervals, and configured to cause the second signal to be applied to the third electrode at second set time intervals, wherein the second set time intervals are different from the first set time intervals.

3. The sensor device according to claim 1, wherein: the third electrode is located at a second distance from the second electrode; and the second distance is smaller than the first distance.

4. The sensor device according to claim 1, wherein: the first electrode has a first total surface area; the second electrode has a second total surface area; the third electrode has a third total surface area; and at least one of the third total surface area is smaller than the first total surface area, and the third total surface area is smaller than the second total surface area.

5. The sensor device according to claim 1, further comprising: a fourth electrode.

6. A method of operating a capacitive sensor device, comprising: applying a first electrical signal to a first electrode with a first signal generation device; emitting a first electrical field with the first electrode using the applied first electrical signal; picking up the emitted first electrical field with a second electrode located at a first distance from the first electrode; applying a second electrical signal to a third electrode with a second signal generation device; emitting a second electrical field with the third electrode using the applied second electrical signal; determining a first measured value with an evaluation device, the first measured value depending on the emitted first electrical field picked up by the second electrode; picking up the emitted second electrical field with the second electrode; determining a second measured value with the evaluation device, the second measured value depending on the emitted second electrical field picked up by the second electrode; and determining a compensated-for measured value using the first measured value and the second measured value.

7. The method according to the claim 6, wherein: applying the first electrical signal to the first electrode comprises periodically applying the first electrical signal to the first electrode; and applying the second electrical signal to the third electrode comprises periodically applying the second electrical signal to the third electrode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and embodiments arise from the attached drawings, in which

(2) FIG. 1 shows a sensor device according to the state of the art;

(3) FIG. 2 shows a schematic representation of a sensor device according to the disclosure;

(4) FIG. 3 shows the sensor device of FIG. 2 in a calibration condition;

(5) FIG. 4 shows the representation of a look-up table;

(6) FIG. 5 shows the representation of a function for evaluating measurement results;

(7) FIG. 6 shows a schematic representation of a further embodiment according to the disclosure;

(8) FIG. 7 shows a further schematic representation of an embodiment according to the disclosure;

(9) FIG. 8 shows a further schematic representation of an embodiment according to the disclosure of a sensor device.

DETAILED DESCRIPTION

(10) FIG. 1 shows a schematic representation of a sensor device 100 according to the state of the art. This sensor device 100 has a first electrode 2 as well as a second electrode 4. These electrodes are arranged on a common carrier 15. Reference sign 22 denotes a signal generation device which emits a signal S to the first electrode 2. This signal generates an electrical field E. This electrical field E is picked up partly by the second electrode 4 and in this way a displacement current is induced which can accordingly be measured. Here, objects also have an effect on the electrical field, for example, which are in an area between electrodes 2 and 4, however also those which are present in a distant area between the two electrodes 2 and 4.

(11) Admittedly, disturbances or objects such as water films, pollutants or the like also affect the measurement.

(12) FIG. 2 shows in a roughly schematic way a sensor device 1 according to the disclosure. This too again has a first electrode 2 as well as a second electrode 4. Here, a signal S1 is applied to the first electrode 2 via a signal generation device 22 and generates in this way an electrical field E1. This electrical field E1 is picked up by the second electrode 4 which generates a displacement current V1 which in turn can be measured by a measurement device.

(13) The displacement current or a signal corresponding to it can accordingly be emitted via an evaluation device 10 as first measurement signal. The evaluation device 10 therefore advantageously calculates the first measurement signal M1 from the displacement current.

(14) Both electrodes 2 and 4 are configured in flat board form here and are preferably parallel to each other so that the electrical field lines not only extend in a straight line between the electrodes 2, 4 but assume the curved course shown in FIG. 2. In this way, objects in the far region of the two electrodes 2, 4 can also be registered, although this far region is not arranged or does not lie geometrically between the electrodes 2, 4.

(15) It is preferred that the electrodes referred to are arranged on a common carrier. Furthermore, the signal generation device(s) can also be arranged on this carrier.

(16) Reference sign 6 denotes a third electrode which, here, is arranged in the area of the second electrode 4. In the state shown in FIG. 2, this third electrode 6 is not provided with a signal. However, here too a signal generation device 62 is provided which can apply especially an electrical signal to the third electrode 6.

(17) Reference sign 8 denotes a control device which effects the activation of the first electrode 2 as well as the third electrode 6 with a signal. Here, this control device can activate these two signal generation devices 22 and 62 for example at different time intervals. It is pointed out however that the control device 8 as well as the two signal generation devices 22 and 62 can also be accommodated in a common control unit.

(18) FIG. 3 shows a representation of the sensor device 1 shown in FIG. 2. In the situation shown in FIG. 3, it is no longer the case that a signal is applied to the first electrode 2 but rather the third electrode 6. This likewise emits an electrical field E2, however only or in particular in the near region, with the result that this electrical field here likewise is only registered by the second electrode 4. Especially disturbances in the near region of the second electrode 4 also have an effect on this electrical field E2. The measurement signals of the third electrode 6 or the signals emitted by this can be used to capture disturbances in the near region of the sensor device or calibrate values appropriately.

(19) Once again, a displacement current can be emitted to the evaluation device 10 in reaction to this field E2, which calculates from this a second measurement signal M2. Further, the evaluation device or a processor device (not shown) can determine a compensated-for signal M.sub.compensated-for from the first measurement signal M1 and the second measurement signal M2.

(20) FIG. 4 shows an example of a two-dimensional look-up table. 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-for measured values M.sub.compensated-for. By using this look-up table, where differing measured values M2 and M1 occur, compensated-for measured values M.sub.compensated-for can be determined in each case or can be determined by interpolation or mean-value formation.

(21) FIG. 5 shows a graphic representation in the context of a further measurement method. Here, a quadratic model function is set out which is applied to a two-dimensional table of values. Here, the boundary conditions are denoted by the reference signs R. As mentioned above, further supporting points can also be taken from a calibration process to help establish parameters of the model.

(22) Besides the arrangement of the other electrode shown in FIG. 2, further arrangements of the electrodes are also conceivable.

(23) So, for example, FIG. 6 shows an example in which the third electrode 6 encompasses the second electrode or measuring electrode. FIG. 7 shows a configuration in which the third electrode is positioned to the side next to the second electrode or measuring electrode. What is common to all these arrangements is however that the third electrode occupies a small area compared to the transmitter electrode or the first electrode 1 and is set a shorter distance away from the measuring electrode 4.

(24) Besides, it is advantageous for being able to compensate for water drops, water running down and mechanical changes in the near region of the sensor device with all arrangements if the third electrode or compensation electrode can operate freely in the direction of that area in space in which the electrical field exists between the transmitter electrode and the measuring electrode. Reference signs E2 denote, as the case may be, the field lines found when measuring the electrical fields emitted by the third electrode. With the situation shown in FIG. 6 and FIG. 7, the third electrode is activated in each case and so the operating mode compensation for the environmental influence applies with the third electrode as active transmitter electrode.

(25) FIG. 8 shows a further configuration of a sensor device according to the disclosure. With this configuration, the sensor device has two compensation electrodes. The sensor device with the single compensation electrode 6 is here supplemented by a second compensation electrode 16 or a fourth electrode 16. This electrode is placed near the first electrode 2, for example here within the first electrode 2.

(26) This electrode 16 is preferably connected as the second measuring electrode and preferably picks up a measured value M3 in the “electrode 2 activated” mode of operation. Here, the fourth electrode 16 is configured and arranged so that the field between the first electrode or transmitter electrode 2 and the fourth electrode 16 is concentrated spatially on the near region of the transmitter electrode, in other words, of the first electrode 2.

(27) Besides the configuration shown in FIG. 8, other configurations would also be possible, especially for example combinations with the configurations shown in FIGS. 6 and 7.

(28) Two further electrodes or compensation electrodes 6, 16 are thus preferably provided with the configuration in FIG. 8 in addition to the first and second electrodes, which in this way enable near-region detection both in the region of the first electrode and in the region of the second electrode.

(29) The applicant reserves the right to claim all features disclosed in the application documents as essential to the disclosure in so far as they are, individually or in combination, novel over the state of the art. It is further pointed out that, in the individual figures, features were also described which, taken in themselves, can be advantageous. A person skilled in the art recognizes straightaway that a particular feature described in a figure can be advantageous even without the adoption of further features from this figure. Furthermore, a person skilled in the art recognizes that advantages can also be gained through a combination of several features shown in individual or differing figures.

LIST OF REFERENCE SIGNS

(30) 1 sensor device 2 first electrode 4 second electrode 6 third electrode 8 control device 10 evaluation device 15 carrier 16 compensation electrode, fourth electrode 18, 22, 62 signal generation device 100 sensor device (state of the art) E, E1,E2 electrical field M1, M2, M3 measured values M.sub.compensated-for compensated-for measured value E field lines R boundary conditions S, S1, S2, S3 (electrical) signal V1 displacement current