OPERATOR CONTROL DEVICE FOR A VEHICLE AND METHOD FOR OPERATING SUCH AN OPERATOR CONTROL DEVICE

Abstract

An operator control device for a vehicle, and a method for operating such an operator control device is disclosed. The operator control device is for controlling safety-relevant functions. To this end, the operator control device has at least one user interface having at least one user input panel for user input and a sensor system for identifying a user input in the area of the user input panel, wherein the sensor system has at least one capacitive sensor device having a first, electrically conductive sensor structure and a second, capacitive sensor device having a second, electrically conductive sensor structure, the sensor structures being arranged beneath the user interface in the area of the user input panel. The first sensor structure and the second sensor structure are each configured in comb-like and/or meanderous fashion and arranged in intermeshing fashion at least in a subarea of the user input panel.

Claims

1. An operator control device controlling safety-relevant functions associated with a vehicle, the operator control device comprising: at least one user interface having at least one user input panel for user input and a sensor system for identifying a user input in the area of the user input panel, wherein the sensor system has at least one first, capacitive sensor device having a first, electrically conductive sensor structure and a second, capacitive sensor device having a second, electrically conductive sensor structure, the sensor structures being arranged beneath the at least one user interface in the area of the user input panel wherein the first sensor structure and the second sensor structure are each configured in comb-like and/or meanderous fashion and arranged in intermeshing fashion at least in a subarea of the user input panel.

2. The operator control device according to claim 1, wherein the at least one user interface has multiple user input panels each having an associated sensor system for identifying a user input in the area of the associated user input panel, wherein each sensor system associated with a user input panel has at least one first, capacitive sensor device having a first, electrically conductive sensor structure and a second, capacitive sensor device having a second, electrically conductive sensor structure, the sensor structures each being arranged beneath the user interface of the associated user input panel, and wherein the first sensor structure and the second sensor structure are each configured in comb-like and/or meanderous fashion and arranged in intermeshing fashion at least in a subarea of the associated user input panel.

3. The operator control device according to claim 2, wherein at least two first sensor structures or two second sensor structures of two sensor systems are electrically connected to one another.

4. The operator control device according to claim 1, wherein at least one sensor system is configured to register, in comparison with a reference state, a respective change in the capacitive coupling of the first sensor structure to the surroundings and/or a reference electrode and a change in the capacitive coupling of the second sensor structure to the surroundings and/or a reference electrode, a wherein the change in the capacitive coupling that is caused as a result of a user input in the area of the user input panel.

5. The operator control device according to claim 4, wherein: the sensor system is configured to register the change in the capacitive coupling of at least one sensor structure to the surroundings, in a first scanning cycle a reference capacitance and a measurement capacitance, formed by the sensor structure and the surroundings, are each charged with a defined electrical potential in a first step, the reference capacitance being charged with a first, defined electrical potential and the measurement capacitance being charged with a second, defined electrical potential, the reference capacitance and the measurement capacitance formed by the sensor structure and the surroundings is shorted in a further second step, and the resulting electrical potential arising between the measurement capacitance and the reference capacitance is registered as a sensor signal in a further third step, the resulting electrical potential arising on the basis of the first and second electrical potentials, the magnitude of the reference capacitance and the magnitude of the measurement capacitance (C.sub.Surroundings).

6. The operator control device according to claim 5, wherein the sensor system is configured such that in a further scanning cycle, the reference capacitance is charged with the second electrical potential and the measurement capacitance is charged with the first electrical potential in the first step, the reference capacitance and the measurement capacitance (C.sub.Surroundings) formed by the at least one sensor structure and the surroundings are shorted in a further fourth step, and the resulting electrical potential arising between the measurement capacitance and the reference capacitance is registered as a sensor signal in a further fifth step, the resulting electrical potential arising on the basis of the first and second potentials, of the magnitude of the reference capacitance and the magnitude of the measurement capacitance.

7. The operator control device according to claim 4, wherein at least one sensor system has a reference electrode, wherein the reference electrode has a defined electrical potential applied to the reference electrode, and the sensor system is configured such that a user input in the area of the user input panel causes a registerable change in a capacitive coupling of at least one sensor structure to the reference electrode in comparison with a reference state.

8. The operator control device according to claim 7, wherein the sensor system is configured such that in a further scanning cycle, the reference electrode has a defined electrical potential applied to it in a first step, and the capacitive coupling of at least one sensor structure to the reference electrode can be registered in a further second step.

9. The operator control device according to claim 4, wherein the sensor system is configured to register the change in the capacitive coupling of at least one sensor structure to the surroundings and the change in the capacitive coupling of this sensor structure to the reference electrode in succession alternately.

10. The operator control device according to claim 7, wherein at least one sensor structure of at least one sensor system is also connected as a reference electrode, and the first sensor structure and the second sensor structure are each connected as a reference electrode in turn.

11. The operator control device according to claim 1, wherein at least one sensor system has a screening device having at least one screening element, wherein the screening device is configured to screen the first sensor device and/or the second sensor device from perturbing capacitive couplings to components of the operator control device (10), the screening element being formed by an electrically conductive screening structure that is arranged between the first sensor structure of the first sensor device and the second sensor structure of the second sensor device of the sensor system.

12. The operator control device according to claim 11, wherein the screening element can have a defined, electrical potential, that is at least sometimes tracked to a potential applied to the sensor structure during the registering of the change in the capacitive coupling of the sensor structure wherein the potential follows the profile of the potential applied to the sensor structure during registering of the change in the capacitive coupling of a sensor structure of the sensor system.

13. The operator control device according to claim 12, wherein at least one sensor structure of at least one sensor system can also be connected as an active screening element, wherein the first sensor structure and the second sensor structure can each be connected as an active screening element in turn.

14. The operator control device according to claim 1, wherein at least one sensor system has not only the first capacitive sensor device and the second capacitive sensor device but also at least one further sensor device for identifying a user input in the area of the user input panel associated with the sensor system, preferably a pressure-sensitive sensor device.

15. The operator control device according to claim 4, wherein at least one sensor system is configured to register the change in the capacitive coupling of the sensor structure of the first capacitive sensor device and of the sensor structure of the second sensor device of the sensor system to the surroundings and/or to a reference electrode at the same time or to register said change at such slightly staggered times that safety-relevant plausibilization of the captured sensor signals is possible.

16. The operator control device according to claim 4, wherein at least one sensor system is configured to register the change in the capacitive coupling of the sensor structure of a capacitive sensor device to the surroundings and/or to a reference electrode only if a user input has been identified beforehand during the registering of the change in the capacitive coupling of the sensor structure of the other sensor device to the surroundings and/or to a reference electrode.

17. The operator control device according to claim 1, further comprising a monitoring device for identifying a fault state in at least one sensor system, wherein the monitoring device is configured to plausibilize at least one captured sensor signal of at least one sensor device of the sensor system, to plausibilize the sensor signals of all of the sensor devices of the sensor system, wherein the monitoring device identifies a fault if at least one captured and evaluated sensor signal of the sensor system is implausible, the monitoring device being configured to take at least one captured sensor signal of the first sensor device and at least one captured sensor signal of the second sensor device and/or to take the directly successively registered changes in the capacitive coupling of a sensor structure to the surroundings and in the capacitive coupling of this sensor structure to the reference electrode as a basis for identifying whether there is a fault state.

18. The operator control device according to claim 1, wherein the operator control device has a lighting device having at least one light-emitting source for lighting the back of at least one user input panel, wherein the at least one light-emitting source is arranged in a plane beneath at least one sensor structure of the sensor system associated with the control panel, beneath the sensor structure of the first capacitive sensor device and beneath the sensor structure of the second capacitive sensor device of the sensor system associated with the control panel.

19. The operator control device according to claim 18, wherein all the sensor structures of the sensor system are configured and/or arranged such that a beam path from the at least one light-emitting source to the user input panel is not blocked.

20. The operator control device according to claim 18, wherein all the structures of the sensor system including the first and second sensor structures, are configured in such a transparent fashion that they are transmissive at least for a portion of the radiation emitted by the at least one light-emitting source.

21. The operator control device according to claim 18, wherein at least one sensor structure comprises or is manufactured from indium tin oxide, fluorine-doped tin oxide, aluminium-doped tin oxide, antimony-doped tin oxide and/or graphene.

22. A method for operating an operator control device that is configured according to claim 1, wherein the operator control device has at least one user interface having at least one user input panel for user input and a sensor system for identifying user input in the area of the user input panel, wherein the sensor system has at least one first, capacitive sensor device having a first, electrically conductive sensor structure and a second, capacitive sensor device having a second, electrically conductive sensor structure, the sensor structures being arranged beneath the user interface in the area of the user input panel, the method comprising: to identify a user input, registering the change in the capacitive coupling of the first sensor structure to the surroundings and/or a reference electrode and a change in the capacitive coupling of the second sensor structure to the surroundings and/or a reference electrode, wherein registering the change in the capacitive coupling of at least one sensor structure to the surroundings comprises, in a first scanning cycle, charging each of a reference capacitance and a measurement capacitance, formed by the sensor structure and the surroundings with a defined electrical potential; charging the reference capacitance with a first, defined electrical potential and the measurement capacitance being charged with a second, defined electrical potential, in a first step; shorting the reference capacitance and the measurement capacitance formed by the sensor structure and the surroundings are shorted in a further second step; and registering the resulting electrical potential arising between the measurement capacitance and the reference capacitance is registered as a sensor signal in a further third step, the resulting electrical potential arising on the basis of the first and second electrical potentials and also on the basis of the magnitude of the reference capacitance and on the basis of the magnitude of the measurement capacitance.

23. The method according to claim 22, further comprising, in a further second scanning cycle, charging the reference capacitance with the second electrical potential and charging the measurement capacitance with the first electrical potential in the first step, shorting the reference capacitance and the measurement capacitance formed by the at least one sensor structure and the surroundings in a further fourth step, and registering the resulting electrical potential arising between the measurement capacitance and the reference capacitance as a sensor signal in a further fifth step, the resulting electrical potential arising on the basis of the first and second potentials and also on the basis of the magnitude of the reference capacitance and on the basis of the magnitude of the measurement capacitance.

24. The method according to claim 22, wherein at least one sensor system of the operator control device has a reference electrode and the sensor system is configured such that a user input in the area of the user input panel causes a registerable change in a capacitive coupling of at least one sensor structure to the reference electrode in comparison with a reference state, wherein, in a further scanning cycle, the reference electrode has a defined electrical potential applied to it in a first step, and the capacitive coupling of the sensor structure to the reference electrode is registered in a further step.

25. The method according to claim 24, wherein at least one sensor structure of at least one sensor system is at least intermittently connected as a reference electrode.

26. The method according to claim 22, wherein at least one sensor system has a screening device having at least one electrically conductive screening element for screening the first sensor device and/or the second sensor device from perturbing capacitive couplings to components of the operator control device, wherein the screening element has a defined, electrical potential that is at least sometimes tracked to a potential that is applied to the sensor structure during the registering of the change in the capacitive coupling of the sensor structure, wherein the electrical potential follows the profile of the potential applied to the sensor structure, applied to it during registering of the change in the capacitive coupling of at least one sensor structure of the sensor system.

27. The method according to claim 26, wherein both sensor structures of at least one sensor system is intermittently operated in turn as an active screening element.

28. The method according to claim 22, wherein at least the change in the capacitive coupling of the sensor structure of the first capacitive sensor device and of the sensor structure of the second sensor device of the sensor system to the surroundings and/or to a reference electrode are registered at the same time or at slightly staggered times that safety-relevant plausibilization of the captured sensor signals is possible, wherein a user input in a user input panel is registered by all the sensor devices of the sensor system of the associated user input panel at the same time or at slightly staggered times.

29. The method according to at least claim 22, wherein the change in the capacitive coupling of the sensor structure of a sensor device to the surroundings and/or to a reference electrode is registered only when a user input has been identified beforehand during the registering of the change in the capacitive coupling of the sensor structure of the other sensor device to the surroundings and/or to a reference electrode.

30. The method according to claim 22, wherein when a user input on a user input panel is identified, a function associated with the user input panel is triggered only if no fault state in the sensor system has been identified.

31. The method according to claim 30, wherein the user interface has multiple user input panels, wherein each user input panel has an associated sensor system for identifying a user input in the area of the associated user input panel, wherein each sensor system associated with a user input panel has at least one first, capacitive sensor device having a first, electrically conductive sensor structure and a second, capacitive sensor device having a second, electrically conductive sensor structure, the sensor structures each being arranged beneath the user interface of the associated user input panel, wherein when a user input has been identified, a function is triggered only if a user input has been identified only in a single user input panel.

32. The method according to claim 22, wherein the operator control device has a monitoring device for identifying a fault state in at least one sensor system, wherein the monitoring device is used to plausibilize at least one sensor signal of at least one sensor device of at least one sensor system, wherein a fault state is identified if at least one captured and evaluated sensor signal is implausible, a fault state being identified if at least one captured sensor signal of the first sensor device is implausible by comparison with at least one captured sensor signal of the second sensor device and/or if the directly successively registered changes in the capacitive coupling of at least one sensor structure to the surroundings and in the capacitive coupling of this sensor structure to the reference electrode are implausible.

Description

[0070] The invention will now be explained in more detail on the basis of preferred exemplary embodiments, particularly with reference to the accompanying drawings, in which.

[0071] FIG. 1 shows a schematic depiction of a section through an exemplary embodiment of an operator control device according to the invention,

[0072] FIG. 2 schematically shows a plan view of the configuration and arrangement according to the invention of the sensor structures of the capacitive sensor devices of the operator control device according to the invention from FIG. 1,

[0073] FIG. 3 schematically shows a possible, alternative configuration and arrangement of the sensor structures for an alternative exemplary embodiment of an operator control device according to the invention,

[0074] FIGS. 4 to 6 schematically show possible, alternative configurations and arrangements of the sensor structures for an alternative exemplary embodiment of an operator control device according to the invention,

[0075] FIG. 7 shows a detail from a schematic block diagram of a capacitive sensor device for an operator control device according to the invention in order to clarify the manner of operation of the capacitive sensor device,

[0076] FIG. 8 shows a detail from a schematic block diagram of a sensor system of the operator control device according to the invention from FIG. 1,

[0077] FIG. 9 schematically shows the profile of the electrical potential applied to a sensor structure of the operator control device according to the invention during the registering of a change in the capacitive coupling of a sensor structure to the surroundings,

[0078] FIG. 10 schematically shows the profile arising in contrast to FIG. 9 for the electrical potential applied to the sensor structure of the capacitive sensor device when steps T1 and T2 and also T4 and T5 are respectively repeated during the registering of the change in the capacitive coupling,

[0079] FIG. 11 shows an advantageous profile of a tracked electrical potential of an active screening element,

[0080] FIG. 12 shows a particularly advantageous profile of an electrical potential of an active screening element, the potential of the screening element in this case, in contrast to FIG. 10, following the profile of the electrical potential applied to the sensor structure.

[0081] FIG. 1 shows an exemplary embodiment of an operator control device 10 according to the invention having an input screen 11 as a user interface 12, a user input being possible by using a finger 13 to touch the user interface 12 in the manner of a keystroke. In this case, the operator control device 10 according to the invention is provided for the purpose of controlling various, including safety-relevant, functions in a vehicle.

[0082] This exemplary embodiment of an operator control device 10 according to the invention has a sensor system having multiple sensor devices 14a, 14b and 16, the sensor devices 14a and 14b each being capacitive sensor devices 14a, 14b while the sensor device 16 is a pressure-sensitive sensor device in the form of a force sensor.

[0083] The sensor devices 14a, 14b and 16 of the sensor system of the operator control device according to the invention are each electronically coupled to a printed circuit board, the printed circuit board having a microcontrollernot depicted herefor evaluating the captured sensor signals.

[0084] From FIG. 2, which schematically shows a plan view of the configuration and arrangement according to the invention of the sensor structures 19 and 20 of the capacitive sensor devices of the operator control device according to the invention from FIG. 1, it is possible to see that the capacitive sensor devices 14a and 14b each have a sensor structure 19 and 20, respectively, beneath a user input panel 18 associated with the sensor devices 14a and 14b, the first capacitive sensor device 14a having the sensor structure 19 associated with it and the sensor structure 20 being associated with the capacitive sensor device 14b. The sensor structures 19 and 20 in this arrangement are each mounted on the back of the glass plate of the input screen 11 that forms the user interface 12.

[0085] According to the invention, the first sensor structure 19 and the second sensor structure 20 in this arrangement are each formed by electrical conductors configured in comb-like fashion that are arranged in intermeshing fashion in a common plane parallel to the user interface 12.

[0086] The first sensor device 14a and the second capacitive sensor device 14b in this arrangement are each configured to identify a touch of the user interface 12 in a respective common user input panel 18 associated with the two sensor devices 14a and 14b, whereas the pressure-sensitive sensor device 16 does not react just to mere touching of the user interface 12, but rather reacts only when the finger 13 is used to apply a pressure exceeding a threshold value to the user interface 12 or the associated user input panel.

[0087] The identification of a user input by means of the capacitive sensor devices 14a, 14b is effected on the basis of what is known as the capacitive principle in this case, which involves an approach by a human hand or a finger 13, in particular a touch of the user interface 12, in the detection area of the associated sensor devices 14a, 14b causing a change in the capacitive couplings of the relevant sensor structures 19, 20 to the surroundings and, if present, to a reference electrode, the change in the capacitive coupling being able to be registered by metrology. From the registered changes in the capacitive couplings of the sensor structures 19, 20 to the surroundings and/or to the reference electrode, it is then possible to infer a user input.

[0088] In this exemplary embodiment of an operator control device according to the invention, the user interface 12 is further lit, the lighting of the user interface 12 being provided by a light-emitting source 17 arranged at the back in the form of an LED that is configured to illuminate the user interface 12 from the back, the user interface 12 being of accordingly transparent configuration, so that the light is also perceived as lighting by a user.

[0089] So that the rays of light emitted by the light-emitting source are not blocked by the sensor devices 14a and 14b, in particular the sensor structures 19, 20 thereof, the latter are of accordingly translucent configuration and in particular manufactured from indium tin oxide and vapour-deposited on the back of the user interface 12.

[0090] The respective comb-like configuration according to the invention and the meshing arrangement of the first sensor structure 19 and the second sensor structure 20 beneath an associated, common user input panel 18 allows redundant registering of a user input in a simple manner, the sensor structures 19 and 20 being arranged at such a short distance from one another that every user input results in a change in the capacitive coupling of the two sensor structures 19, 20 to the surroundings and/or a reference electrode. The microcontrollernot denoted in more detail hereon the printed circuit board 15 can be used to evaluate the two captured sensor signals of the first sensor device 14a and the second sensor device 14b in parallel. In particular, a redundant evaluation required for safety-relevant functions is possible, the captured sensor signals first being able to be compared with one another and secondly being able to be used for reciprocal plausibilization.

[0091] The sensor structures 19 and 20 in this arrangement are used not only for registering capacitive coupling to the surroundings and/or to a reference electrode, not depicted here, but rather can furthermore at least each be connected as an active screening element and as a reference electrode.

[0092] FIG. 3 schematically shows a possible, alternative configuration and arrangement of the sensor structures 19 and 20 for an alternative exemplary embodiment of an operator control device according to the invention, wherein in this exemplary embodiment the input screen 11 has two user input panels 18, each user input panel 18 having an associated sensor system with in each case a first sensor structure 19 and a second sensor structure 20. The sensor structures 19 and 20 of a sensor system are each arranged beneath the associated user input panel 18 and each configured in comb-like fashion and each arranged in intermeshing fashion, so that respective redundant registering of a user input by means of the first sensor structure 19 and the second sensor structure 20 is possible in each user input panel 18.

[0093] To simplify the design of an operator control device according to the invention, the first sensor structures 19 are respectively connected to one another, so that only one connection contact is necessary for electrical coupling to the printed circuit board 15 and the microcontroller. A further advantage of a common sensor structure 19 is that this sensor structure 19 can be used as a control sensor for all of the sensor systems of the operator control device 10 at the same time, which allows particularly simple and effective plausibilization of the captured sensor signals.

[0094] FIGS. 4 to 6 schematically show further possible, alternative configurations and arrangements of the sensor structures 19 and 20 for an operator control device according to the invention, the sensor system shown in FIG. 4 having a meanderously configured, further electrical conductor 21 provided between the first sensor structure 19 and the second sensor structure 20, which further electrical conductor is likewise arranged in the same plane as the first sensor structure 19 and the second sensor structure 20 in this exemplary embodiment and is connectable and can be operated as an active screening element. To this end, the electrical conductor 21 can in particular have a defined, electrical potential UAE applied to it that is tracked to or follows the sensor signal applied to one of the sensor structures 19 and 20, while the change in the capacitive coupling of at least one sensor structure 19 or 20 to the surroundings and/or to a reference electrode, not depicted here, is registered, cf. FIGS. 11 and 12.

[0095] In the case of the sensor structures 19 and 20 shown in FIG. 5, in contrast to the previous exemplary embodiments, the sensor structure 20 is not configured in comb-like fashion like the sensor structure 19, but rather is meanderous, but, according to the invention, likewise arranged so as to mesh with the first sensor structure 19.

[0096] FIG. 6 shows a further exemplary embodiment for the configuration and arrangement of the sensor structures 19, 20 of an operator control device according to the invention, with the first sensor structure 19 and the second sensor structure 20 each being configured meanderously in this case, but likewise, according to the invention, being arranged in intermeshing fashion.

[0097] In the case of the operator control device according to the invention described above, a user input is identified first by means of the pressure-sensitive sensor device 16 and also by means of the first capacitive sensor device 14a and the second capacitive sensor device 14b using a method according to the invention.

[0098] To clarify the manner of operation of the capacitive sensor devices 14a and 14b, particularly to explain the method according to the invention, FIG. 7 shows a detail from a schematic block diagram of a capacitive sensor device for an operator control device according to the invention. An associated, exemplary potential profilearising when a method according to the invention is usedof a potential U.sub.Sensor applied to a sensor structure 19 is depicted in FIG. 9.

[0099] A user input is identified, in particular the capacitive coupling of a sensor structure is registered, using a method according to the invention, which is subsequently described by way of example on the basis of the sensor structure 19, by virtue of, during a first scanning cycle AZ1, the reference capacitance 22 and the sensor structure 19 capacitively coupled to the surroundings being charged in defined fashion in a first step in the period T1, for example the reference capacitance being charged with 5V and the sensor structure 19, as shown, with 0V, and subsequently the reference capacitor 22 and the sensor structure 19 being shorted in a second step T2. In a third step in a period T3, an evaluation device 23, which in this exemplary embodiment is the microcontroller arranged on the printed circuit board, then registers and evaluates the potential U.sub.Sensor arising between the reference capacitance 22 and the sensor structure 19. From the potential U.sub.Sensor arising on the sensor structure 19, which potential conveys the capacitive coupling of the sensor structure 19 to the surroundings, it is subsequently possible to infer whether or not there is a human hand or a finger 13 etc. in the detection area of the sensor device 14a or whether or not a user input has been made.

[0100] The reference capacitance 22 is charged by virtue of first of all the switches SW1 and SW3 being closed and the switch SW2 being opened. The measurement capacitance C.sub.Surroundings is charged by virtue of the switches SW3 and SW1 being opened and the switch SW2 being closed. Once the measurement capacitance C.sub.Surroundings is charged, the switch SW2 is subsequently likewise opened again.

[0101] The shorting is then effected by closing the switch SW3 and causes the same potential U.sub.Sensor to arise on the reference capacitance 22 and the measurement capacitance C.sub.Surroundings, the resulting electrical potential U.sub.Sensor fundamentally arising on the basis of the first and second electrical potentials and also on the basis of the magnitude of the reference capacitance 22 and on the basis of the magnitude of the measurement capacitance C.sub.Surroundings. If the measurement capacitance C.sub.Surroundings is of approximately the same magnitude as the reference capacitance 22, then approximately a potential U.sub.Sensor of half the amplitude arises, i.e. in this case an amplitude of 5V prompts a potential of approximately 2.5V to arise on the sensor structure 19.

[0102] If there is no human hand or no finger 13 or the like in the detection area of the sensor device or of the sensor structure 19, then a potential profile U.sub.Sensor1 arises. If, by contrast, there is a human hand or a finger 13 or the like in the detection area of the sensor structure 19, then a different potential profile is obtained, depicted here by the potential profile U.sub.Sensor2 by way of example. From the potential U.sub.Sensor1 or U.sub.Sensor2 that is obtained, it is possible to infer the presence or absence of a human hand 13 in the detection area of the sensor structure 19.

[0103] During the registering of the potential U.sub.Sensor applied to the sensor structure 19 and to the reference capacitance 22, it is possible, if the switch SW3 is open again, for the sensor structure 19 to already have a defined potential applied to it again, for example for a next scan to identify a user input or for another purpose.

[0104] To further improve registering accuracy, it is additionally possible for, in a second scanning cycle AZ2, the reference capacitance 22 also to be subsequently charged with the second electrical potential of 0V and for the measurement capacitance C.sub.Surroundings to be charged with the first electrical potential of 5V in the first step T4, that is to say conversely with respect to the first scanning cycle AZ1.

[0105] In a further step T5, the reference capacitance 22 and the measurement capacitance C.sub.Surroundings formed by the sensor structure 19 and the surroundings are then shorted again and, in a further step T6, it is again possible for the resulting electrical potential U.sub.Sensor arising between the measurement capacitance C.sub.Surroundings and the reference capacitance 22 to be registered.

[0106] As a result, potential differences U1 and U2 are obtained that can be evaluated, instead of absolute potential values U.sub.Sensor1 and U.sub.Sensor2, which allows better identification accuracy to be attained. In particular, it is no longer necessary in this case to correct or remove perturbing, steady-state, capacitive couplings affecting the absolute potential values U.sub.Sensor1 and U.sub.Sensor2, or to calibrate the sensor device 14a, 14b accordingly in this regard.

[0107] To increase registering accuracy, particularly to improve the resolution for measurement and reference capacitances 22 of different magnitude, it is advantageous to repeat the first two steps T1 and T2 and also T4 and T5 of the first scanning cycle AZ1 and of the second scanning cycle AZ2 in each case, see FIG. 10, since in this manner the resulting potential U.sub.Sensor approaches half the potential difference.

[0108] FIG. 8 shows a detail from a schematic block diagram of the capacitive sensor devices 14a and 14b of the operator control device 10 according to the invention from FIG. 1, wherein, in contrast to the depiction in FIG. 7, which merely serves for explanation, the sensor structure 20 in the case of the operator control device 10 according to the invention is additionally connectable as a reference electrode 20 by means of the switches SW4, SW5 and SW6 and can have a defined electrical potential applied to it, so that the capacitive coupling of the first sensor structure 19 to a reference electrode, which in this case is formed by the second sensor structure 20, can be registered, with a user input in the detection area of the first sensor structure 19 causing a registerable change, associated with the sensor structure 19, in a capacitive coupling C.sub.Ref of the sensor structure 19 to the reference electrode 20 in comparison with the reference state.

[0109] In this case, it has been found to be particularly advantageous if the reference electrode 20 is connected in a further scanning cycle, particularly in a second scanning cycle AZ2 and/or a third and/or fourth scanning cycle, since this causes an increase in the potential difference U.sub.1 or U.sub.2 when the potential applied to the reference electrode 20 is chosen accordingly, as a result of which a better resolution and hence a higher identification accuracy can be achieved. That is to say that the potential profiles U.sub.Sensor1 and U.sub.Sensor2 are then at a different level.

[0110] It is particularly advantageous if the change in the capacitive coupling of the sensor structure 19 to the surroundings and the change in the capacitive coupling of the sensor structure 19 to the reference electrode 20 are registered in direct succession, in particular in turn, particularly preferably alternately. This allows a particularly high identification accuracy to be achieved, since a multiplicity of potential values U.sub.Sensor1 and U.sub.Sensor2 or potential differences U.sub.1 and U.sub.2 are available that can be offset against one another almost arbitrarily in order to remove or compensate for measurement errors and steady-state offsets or the like and/or to increase the resolution and hence the accuracy or sensitivity of the sensor device.

[0111] Preferably, the capacitive coupling of the first sensor structure 19 to the surroundings and to a reference electrode, wherein the second sensor structure 20 forms the reference electrode, and subsequently, but only at such slightly staggered times that plausibilization of the sensor signals of the first and second sensor devices that is required for safety-relevant functions continues to be possible, the capacitive coupling of the second sensor structure 20 to the surroundings and to a reference electrode, wherein in this case the first sensor structure 19 forms the reference electrode, is registered in each case alternately in turn.

[0112] If an operator control device according to the invention has an additional screening element, for example, as depicted in FIG. 4, in the form of a further electrical conductor 21 or a sensor structure operable as a screening element, then the screening element has a defined electrical potential, particularly a potential U.sub.AE tracked to or following the potential applied to the relevant sensor structure, see FIGS. 11 and 12, applied to it preferably during the registering of the capacitive coupling of a sensor structure to the surroundings and/or to a reference electrode, FIG. 11 schematically showing an exemplary, advantageous profile of a tracked electrical potential U.sub.AE that can be applied to an active screening element.

[0113] In this case, the potential U.sub.AE increases when the potential U.sub.Sensor applied to the sensor structure increases and decreases when the potential U.sub.Sensor applied to the sensor structure decreases. Such application of potentials to a screening element already allows good screening performance to be achieved.

[0114] A potential profile U.sub.AE of this kind can be achieved through the use of a sensor system having a microcontroller from the Microchip company, for example, by virtue of the relevant screening element being electrically connected to an I/O pin provided specifically for that purpose on the microcontroller. The microcontroller is accordingly configured to apply the shown potential profile to this pin on the basis of the state of the sensor device.

[0115] For even better screening, the defined electrical potential U.sub.AE applied to the screening element should follow the electrical potential U.sub.Sensor applied to the sensor structure as well as possible, preferably as depicted in FIG. 12. FIG. 12 schematically shows the profile of an electrical potential U.sub.AE of an active screening element that has almost the same curved profile with almost the same absolute potential values as the electrical potential U.sub.Sensor applied to the sensor structure and therefore follows the profile of the electrical potential U.sub.Sensor applied to the sensor structure.

[0116] This potential profile U.sub.AE can likewise be achieved by the use of a sensor system having a microcontroller from the Microchip company, the relevant screening element in this case being connected to a different pin provided for that purpose on the microcontroller, specifically to what is known as the DACOUT pin. The microcontroller is accordingly configured to apply the shown potential profile to this pin on the basis of the state of the sensor device.

[0117] Naturally, a multiplicity of modifications, in particular of design type, are possible without departing from the content of the patent claims.