Patent Publication Number: US-2017353133-A1

Title: Device and method for sensing a rotational position of a rotatable element, controller, sensor system for detecting a rotational position of a rotatable element, and household appliance

Description:
CROSS-REFERENCE TO PRIOR APPLICATION 
     Priority is claimed to German Patent Application No. DE 10 2016 110 085.4, filed on Jun. 1, 2016, the entire disclosure of which is hereby incorporated by reference herein. 
     FIELD 
     The present invention relates to a device for sensing a rotational position of a rotatable element, a method for determining a rotational position of a rotatable element, a corresponding controller, a sensor system for detecting a rotational position of a rotatable element, and a household appliance. 
     BACKGROUND 
     In different product ranges of household appliances, for example, cycle selection and menu navigation may be performed using electromechanical rotary selector switches. Depending on the appliance, incremental or absolute evaluation methods may be used. Rotational movement may be transmitted from the rotary selector switch, for example, through a supported shaft, to a detent mechanism and electronic components for evaluating rotational angles on operating and display electronics. Evaluation of the rotary position on the operating and display electronics may take place, in particular, behind a fascia panel. 
     German Patent Application DE 10 2009 002 623 A1 discloses a program selector for home appliance having a capacitive touch or proximity sensor device. 
     SUMMARY 
     In an embodiment, the present invention provides a device for sensing a rotational position of a rotatable element for a household appliance, the device comprising: a stator having a plurality of capacitive sensor surfaces spaced apart from one another in a plane of extension of the stator; and a rotor rotatably positionable or disposed relative to the stator and having an electrically conductive section and a dielectric non-conductive section, the conductive section being larger in area than the non-conductive section, the rotor being disposed opposite the plane of extension of the stator in a rotatable condition relative to the stator, and the rotor being couplable or coupled to the rotatable element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. Other features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following: 
         FIG. 1  is a schematic view of a household appliance according to an exemplary embodiment of the present invention; 
         FIG. 2  is a schematic view of a sensor system according to an exemplary embodiment of the present invention; 
         FIG. 3  is a schematic view of a stator of a device according to an exemplary embodiment of the present invention; 
         FIG. 4  is a schematic view of a rotor of a device according to an exemplary embodiment of the present invention; 
         FIG. 5  is a schematic top view showing a stator and a rotor superimposed thereon according to an exemplary embodiment of the present invention; 
         FIG. 6  is a flow chart of a determination method according to an exemplary embodiment of the present invention; 
         FIG. 7  is a flow chart of a position determination process according to an exemplary embodiment of the present invention; 
         FIG. 8  is a schematic signal waveform diagram according to an exemplary embodiment of the present invention; 
         FIG. 9  is a schematic signal waveform diagram according to an exemplary embodiment of the present invention; and 
         FIG. 10  is a schematic signal waveform diagram according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In an embodiment, the present invention provides a device for sensing a rotational position of a rotatable element, a method for determining a rotational position of a rotatable element, a corresponding controller, a sensor system for detecting a rotational position of a rotatable element, a household appliance and computer program product having the features of the main claims. 
     In addition to a cost-effective and space-saving design, another particular advantage achievable by the present invention is that it can provide a measuring method for capacitance-based contactless and absolute determination of rotational angles. By dispensing with a ground surface for a stator, there is no need, in particular, to route a wire from such a ground surface at a distance to sensor surfaces of the stator, so that the determination of the rotational position can be performed in a space-saving, cost-effective and uncomplicated manner and, through omission of a ground surface, with an increased sensor surface. Since the ground surface is dispensed with, no interference effects can occur in a supply line to such a ground surface. A surface area that would otherwise be needed for the ground surface can be distributed among the sensor surfaces, thereby making it possible to increase a surface area of each of the sensor surfaces, which in turn makes it possible to obtain a larger raw value as a measured parameter. Thus, it is possible not only to dispense with a wire that would have to be routed in a complex fashion to an otherwise provided ground surface, but to determine the rotational position or rotational angle capacitively, absolutely and reliably, even after a restart or system restart. 
     Presented is a device for sensing a rotational position of a rotatable element, the device including the following features: 
     a stator having a plurality of capacitive sensor surfaces spaced apart from one another in a plane of extension of the stator; and 
     a rotor rotatably positionable or disposed relative to the stator and having an electrically conductive section and a dielectric non-conductive section, the conductive section preferably being larger in area than the non-conductive section, the rotor being disposed opposite the plane of extension of the stator in a rotatable condition relative to the stator, and the rotor being couplable or coupled to the rotatable element. 
     The rotatable element may be a control element, in particular a rotary selector switch, for controlling at least one function of an appliance. The sensor surfaces may extend along the plane of extension of the stator. The non-conductive section may have a dielectric solid, a gap, air gap or an interstice. The conductive section of the rotor is configured to cover or overlap at least one sensor surface when the rotor is in a rotatable condition relative to the stator. In particular, in the rotatable condition relative to the stator, the conductive section of the rotor may be disposed opposite the plane of extension of the stator. The stator may have at least two sensor surfaces, at least three sensor surfaces, or more than three sensor surfaces. 
     In the context of the present invention, the terms “covering” and “overlapping” are meant to refer to a mutually spaced-apart, so that the rotor and the stator do not conductively contact each other, but are spaced apart by a dielectric, and that the projection of the rotor in a direction perpendicular to its direction of rotation at least partially covers or overlaps the stator. The dielectric may be air, plastic, glass or another suitable material. 
     In accordance with an embodiment, the sensor surfaces may be configured and, additionally or alternatively, arranged to intermesh with each other in the plane of extension of the stator. Such an embodiment has the advantage that the determination of the rotational position can be performed reliably and accurately. In the context of the present invention, the term “intermesh” means that the separating lines between sensor surfaces do not extend radially straight from the center of the stator and/or rotor, but in an undulating, zigzag or other meandering pattern. In other words, the sensor surfaces intermesh with each other in the form of one or more indentations and complementary projections at at least one point along the separating line in order to adapt the coverage profile during a rotation of the rotor. 
     Also, the conductive section of the rotor may be configured to cover more than one sensor surface of the stator. In other words, the conductive section of the rotor may be configured to cover or overlap at least two sensor surfaces of the stator. Such an embodiment has the advantage that it enables accurate and reliable determination of the rotational position. 
     Preferably, the conductive section of the rotor is configured to cover at least three sensor surfaces of the stator. This is particularly advantageous because in this constellation, a “middle one” of the three covered sensor surfaces is completely covered, and directly adjacent sensor surfaces are at least partially covered. The signal of this completely covered sensor surface does substantially not change, at least over a certain angular range, when the rotor is rotated because then only the coverage/signal of the surrounding sensor surfaces changes proportionally, while the “middle” sensor surface remains completely covered. This simplifies the determination of the rotor position within this corridor. 
     Also presented is a method for determining a rotational position of a rotatable element disposed on a device, the device including a stator having a plurality of capacitive sensor surfaces spaced apart from one another in a plane of extension of the stator, and a rotor rotatably disposed relative to the stator and having an electrically conductive section and a dielectric non-conductive section, the conductive section being configured to cover at least two, preferably at least three, sensor surfaces of the stator, and the rotor being disposed opposite the plane of extension of the stator in a rotatable condition relative to the stator, the method including the following steps: 
     performing a first series of measurements during which an electrical measuring potential is applied to all sensor surfaces of the stator, and reference signals are read from the sensor surfaces in response to the measuring potential, for example, sequentially, although reading in parallel would, in principle, also be possible, the reference signals representing first capacitance values of the sensor surfaces, which are dependent on a position of the rotor; 
     executing a second series of measurements during which the electrical measuring potential is applied to one sensor surface to be measured among the sensor surfaces and an electrical ground potential is applied to all other sensor surfaces, and during which each of the sensor surfaces is sequentially traversed as a sensor surface to be measured, and measurement signals are read from the sensor surfaces in response to the measuring potential and the ground potential, the measurement signals representing second capacitance values of the sensor surfaces, which are dependent on a position of the rotor; 
     generating useful signals based on the reference signals and the measurement signals; and 
     processing the useful signals to determine the rotational position of the rotatable element. 
     The method may be carried out in connection with or using an embodiment of the device mentioned above. The method may be executable, in particular, by a controller. Advantageously, a rotary position may also be determined without touching or turning the rotatable element. Thus, the proposed capacitive evaluation method, in combination with the device, can enable reliable determination of an absolute rotary position, even after a power-up/restart and without touching the rotatable element. Series of measurements as well as signal processing can be performed without being based on an evaluation method based on a relative change in capacitance, in which sensor surfaces would be initialized in response to a power-up/restart, and their capacitance would be measured, and in which no change in capacitance could be measured at the sensor surfaces without a change in rotational angle or without touching the rotatable element. 
     In accordance with an embodiment, in the generating step, a difference of the reference signals and the measurement signals may be calculated to generate the useful signals. Such an embodiment has the advantage of making it possible to obtain comparable sensor signals in which interference effects are eliminated. Furthermore, the useful signals may be comparable to previous values, even after a restart of a controller. 
     Also, in the processing step, the useful signals may be equalized based on at least one ratio between a high point and a low point of a useful signal. A high point may be understood to be a maximum in the signal waveform, and a lowest point may be understood to be a minimum in the signal waveform. Such an embodiment has the advantage of allowing a comparability of the signals, and thus an evaluability, to be improved by such percentage-based equalization. 
     Further, in the processing step, the useful signals may be normalized and, additionally or alternatively, inverted. Such an embodiment has the advantage of allowing a presentability, and thus an evaluability, of the useful signals to be improved. 
     In addition, in the processing step, a weighting calculation may be performed on the useful signals. Such an embodiment has the advantage that the determination of the rotational position can be carried out reliably and accurately, allowing signal processing to be performed rapidly and with little computational effort. 
     The useful signal having the highest signal value may be used as a reference signal for the weighting calculation. Based on a position of the sensor surface associated with the reference signal, a corridor may be determined for the rotational position of the rotatable element. The rotational position of the rotatable element may be determined within the determined corridor based on useful signals from sensor surfaces adjacent the sensor surface that is associated with the reference signal. Also, rotational positions and, additionally or alternatively, corridors may be associated with (detent) positions of the rotatable element. Such an embodiment has the advantage that it enables accurate, absolute and reliable determination of the rotational position or rotational angle. 
     In accordance with an embodiment, the steps of executing a second series of measurements, of generating useful signals and of processing the useful signals may be repeated, with measurement signals being read only from a few, preferably only one, of the sensor surfaces in the step of executing a second series of measurements. This may preferably be used, for example, in the off or idle state of the household appliance, to monitor the last position of the rotary selector switch that was detected prior to power-off (e.g., the OFF position); i.e., the one or more sensor surfaces associated with this position. It is only when the OFF position or the associated corridor is exited that the monitoring of all sensor surfaces is continued. This makes it possible, in the off/idle state of the device, to monitor the position of the rotary selector switch in a manner that saves power and processing time, while providing very quick response upon power-up/starting of the appliance. 
     The approach presented here also provides a controller that is adapted for performing, controlling and implementing the steps of a variant of a method presented here in corresponding devices. The object underlying the present invention can also be achieved rapidly and efficiently through this embodiment variant of the present invention in the form of a controller. 
     The controller may be adapted to read input signals and to determine and provide output signals based on the input signals. An input signal may be, for example, a sensor signal which can be read via an input interface of the controller. An output signal may be a control signal or a data signal which can be provided at an output interface of the controller. The controller may be adapted to determine the output signals using a processing instruction implemented in hardware or software. For this purpose, the controller may, for example, include a logic circuit, an integrated circuit or a software module, and may, for example, be implemented as a discrete device or may be included in a discrete device. 
     Also presented is a sensor system for detecting a rotational position of a rotatable element, the sensor system including the following features: 
     an embodiment of the aforementioned device including a stator ( 250 ) having a plurality of capacitive sensor surfaces ( 355 ) spaced apart from one another in a plane of extension of the stator ( 250 ), and a rotor ( 260 ) rotatably disposed relative to the stator ( 250 ) and having an electrically conductive section ( 462 ) and a dielectric non-conductive section ( 464 ), the conductive section ( 462 ) being configured to cover at least two, preferably at least three, sensor surfaces ( 355 ) of the stator ( 250 ), the conductive section ( 462 ) preferably being larger in area than the non-conductive section ( 464 ), and the rotor ( 260 ) being disposed opposite the plane of extension of the stator ( 250 ) in a rotatable condition relative to the stator ( 250 ); and 
     an embodiment of the aforementioned controller, the controller being connectable or connected to the sensor surfaces of the stator of the device in such a manner that it is capable of transmitting signals. 
     The rotatable element may be mounted on the fascia panel of a household appliance. Alternatively, the top surface of the rotatable element may be substantially flush with the panel surface, or further alternatively, the rotatable elements may be configured to be partially sunk into the fascia panel. 
     Thus, an embodiment of the aforementioned device and an embodiment of the aforementioned controller can be advantageously employed or used in the sensor system to detect the rotational position of the rotatable element. The controller may be a microcontroller or the like. 
     There is further presented a household appliance including the following features: 
     a control device having a rotatable element, an operator side and an appliance side facing away from the operator side, the rotatable element being disposed on the operator side; 
     and 
     an embodiment of the aforementioned sensor system, the rotor of the device of the sensor system being coupled to the rotatable element of the control device, and the stator of the device of the sensor system being disposed on the appliance side of the control device. 
     The household appliance may, in particular, be in the form of a laundry-treating appliance, such as, for example, a washing machine, a dryer or the like, a food-treating appliance, such as, for example, a microwave oven, a range or a similar appliance, and may also be adapted for commercial or professional use. The rotatable element may be configured as a rotary selector switch or the like. The rotatable element may be rotatable between a plurality of detent positions. The sensor system allows detection of even and odd detent positions, it being possible to implement a number of detent positions twice that of the sensor surfaces provided on the stator. This can allow an arbitrary number of even and odd detent positions of the rotatable element to be sensed with a constant number of sensor surfaces. When changing between two positions, jumps between the positions may be prevented. 
     In other words, it is possible to sense even and odd detent positions with a constant number of sensor surfaces. With respect to the sensor surfaces, interferences caused, for example, by a centrally disposed ground surface and the supply line thereto may be prevented, and an input of the controller may be dispensed with. During rotation of the rotatable element, jumps between two positions may be prevented. For example, it is also possible to detect intermediate positions. This may be useful to recognize if a detent mechanism got stuck in one position. It is even possible to provide a rotary selector switch which has a large number of sensable positions; i.e., which is virtually or nearly stepless, since when at least three sensor surfaces are provided on the stator, the number of sensable intermediate positions is limited only by the possible resolution of the measurement. 
     In addition, a duration of a complete measurement and calculation cycle can be optimized or shortened as compared to known solutions, such as the one mentioned above, in which a ground wire is used. 
     The measurement method allows each sensor surface on the stator to be activated and deactivated, thus allowing individual sensors to be selectively included in, or excluded from, the first and second series of measurements and further calculation. It is possible to deactivate sensor surfaces until only one sensor surface is active for the measurement process, such as, for example, the one with the greatest portion covered by the rotor. This reduces the measurement cycle time and the computational effort of the controller, and ultimately also the power consumption. The reduction in the number of sensor surfaces of the stator that are to be measured may be used to monitor only an arbitrary one of the positions of the rotary selector switch, which, in an exemplary embodiment, may be the OFF position of the household appliance in question. In a practical application, this would preferably be used during standby mode, whereas in operating mode (ON), it is possible to activate sensing of several or all sensor surfaces. 
     It is also possible to allow the rotatable element to be set to zero in any position or rotational position. This has the advantage of allowing the rotatable element to be mounted in any position, for example during a manufacturing process. Susceptibility to EMC interference (EMC=electromagnetic compatibility) can be reduced or eliminated by the reference measurement or first series of measurements. Since part of the household appliances already have touch controllers, and because of inexpensive system components, it is possible, for example, to implement the presented capacitive determination of rotational angles in a cost-effective manner. 
     In accordance with an embodiment, the control device may have a continuous dielectric housing portion. At least the device of the sensor system and the rotatable element may be disposed on the housing portion. The housing portion may be in the form of a control panel, switch panel, fascia panel or the like, formed, in particular, of a plastic material. Such an embodiment has the advantage that it can enable rotational position determination through the closed switch panel. For this purpose, a wired rotary selector switch may be constructed without penetrating the control panel by positioning the stator behind the control panel and positioning the rotor on the control panel in the rotary selector switch. Position determination may be based on a capacitive measuring method and may be reliably performed even directly after the controller is started. Thus, suitability exists for household appliances whose operating concept provides for the use of rotary selector switches. Depending on the material of the housing portion (plastic, glass, etc.), it is only necessary to give consideration to a material thickness. A resolution achievable by the sensor system is in particular limited only by signal strengths, regardless, for example, of the number of sensor surfaces. 
     Also advantageous is a computer program product or computer program having program code which may be stored on a machine-readable carrier or storage medium, such as a semiconductor memory, a hard-disk memory or an optical memory. If the program product or program is executed on a computer or a controller, then the program product or program can be used to perform, implement and/or control the steps of the method in accordance with one of the above-described embodiments. 
       FIG. 1  schematically shows a household appliance  100  according to an exemplary embodiment of the present invention. Merely by way of example, household appliance  100  is here in the form of a washing machine, a laundry dryer, or a combination washer/dryer appliance. Household appliance  100  has a control device  110  having a rotatable element  120 . 
     For reasons of representation,  FIG. 1  shows only an operator side of control device  110 . The operator side of control device  110  faces a user of household appliance  100  and faces away from an interior of household appliance  100 . Control device  110  further has an appliance side, which faces away from the operator side and faces the interior of household appliance  100 . Rotatable element  120  is disposed on the operator side of control device  110 . Rotatable element  120  is, for example, a rotary selector switch. Rotatable element  120  is rotatable relative to control device  110 . 
     Household appliance  100  further has a sensor system, which is hidden from view in  FIG. 1  for reasons of representation. The sensor system will be discussed in more detail below in connection with control device  110  and rotatable element  120 . 
       FIG. 2  schematically shows a sensor system  230  according to an exemplary embodiment of the present invention. Sensor system  230  is disposed on control device  110  and rotatable element  120  of the household appliance of  FIG. 1 . Alternatively, sensor system  230  may be disposed on a control device and a rotatable element of a similar household appliance. Thus,  FIG. 2  shows control device  110 , rotatable element  120  and sensor system  230 . 
     Sensor system  230  is configured to detect a rotational position of rotatable element  120 . Sensor system  230  has a device  240  for sensing the rotational position of rotatable element  120 ; i.e., a detecting device  240 , and a controller  270  for determining the rotational position of rotatable element  120 . 
     Detecting device  240  has a stator  250  and a rotor  260 . Stator  250  may be understood to mean positionally fixed sensor surfaces which are electrically connected to controller or microcontroller  270 . Stator  250  has a plurality of capacitive sensor surfaces spaced apart from one another in a plane of extension of stator  250 . Stator  250  will be described in greater detail below with reference to  FIG. 3  and  FIG. 5 . Rotor  260  is rotatable relative to stator  250 . Rotor  260  has an electrically conductive section and a dielectric non-conductive section. Although not explicitly shown in  FIG. 2  for reasons of presentation, the conductive section is larger in area than the non-conductive section of rotor  260 . In other words, rotor  260  has a circular copper surface in which a certain angle is left open; i.e., it has a circular segment as a conductive section. The rotor is rotatably supported above the stator, with a dielectric disposed therebetween. 
     Rotor  260  will be discussed in greater detail below with reference to  FIG. 4  and  FIG. 5 . 
     Rotor  260  is disposed opposite the plane of extension of the stator. Moreover, rotor  260  is coupled to rotatable element  120 . In other words, rotatable element  120  is provided with rotor  260 . Stator  250  of detecting device  240  is disposed on the appliance side of control device  110 , while rotor  260  and rotatable element  120  are disposed on the operator side of control device  110 . 
     In accordance with the exemplary embodiment of the present invention shown in  FIG. 2 , control device  110  has a continuous dielectric housing portion or is configured as a continuous dielectric housing portion. In other words, housing portion has no holes therethrough. Detecting device  240  and rotatable element  120  are disposed on the housing portion of control device  110 . 
     Controller  270  is connected to the sensor surfaces of stator  250  of detecting device  240  in such a manner that it is capable of transmitting signals, as symbolized by a double-headed arrow in  FIG. 2 . Controller  270  is, for example, a microcontroller. Alternatively, controller  270  is configured as part of a microcontroller. Controller  270  has a performing device  272 , an executing device  274 , a generating device  276  and a processing device  278 . 
     Performing device  272  is configured to perform a first series of measurements. In particular, performing device  272  is configured to apply an electrical measuring potential to all sensor surfaces of the stator and to read reference signals  282  from the sensor surfaces in response to the applied measuring potential, for example, sequentially, although reading in parallel would, in principle, also be possible. Performing device  272  is further configured to output reference signals  282  to generating device  276  or make them available to generating device  276 . Reference signals  282  represent first capacitance values of the sensor surfaces of stator  250 , which are dependent on a position of rotor  260 . 
     Executing device  274  is configured to execute a second series of measurements. In particular, executing device  274  is configured to apply the electrical measuring potential to one sensor surface to be measured among the sensor surfaces and to apply an electrical ground potential to all other sensor surfaces, to sequentially traverse each of the sensor surfaces as a sensor surface to be measured for the second series of measurements, and to read measurement signals  284  from the sensor surfaces in response to the measuring potential and the ground potential. Executing device  274  is further configured to output measurement signals  284  to generating device  276  or make them available to generating device  276 . Measurement signals  284  represent second capacitance values of the sensor surfaces of stator  250 , which are dependent on a position of rotor  260 . 
     Generating device  276  is configured to read reference signals  282  and measurement signals  284 . Generating device  276  is further configured to then generate useful signals  286  based on reference signals  282  and measurement signal  284 . Generating device  276  is also configured to output useful signals  286  to processing device  278  or make them available to processing device  278 . 
     Processing device  278  is configured to read or receive useful signals  286  and process them so as to determine the rotational position of rotatable element  120 . Processing device  278  is further configured to provide a position signal  288  representing the determined rotational position of rotatable element  120 . In other words, processing device  278  is configured to read useful signals  286  and generate position signal  288  based on useful signals  286 . 
     The measuring potential may also be referred to as shield potential. Sensor surfaces or sensors connected to shield are charged with an image of the sensor surface to be measured or being scanned. A potential difference between the sensor surface to be measured and a sensor surface connected to shield is zero. The ground potential may also be referred to as ground. Sensor surfaces connected to ground are connected directly to the ground potential. A potential difference is detectable between the sensor surface to be measured and the sensor surface connected to ground. 
       FIG. 3  schematically shows a stator  250  of a device or detecting device according to an exemplary embodiment of the present invention. Stator  250  is, for example, the stator of  FIG. 2  or a similar stator. The view of  FIG. 3  shows capacitive sensor surfaces  355 , which are spaced apart from one another in the plane of extension of stator  250 . Merely by way of example, stator  250  has six sensor surfaces  355 . In accordance with the exemplary embodiment of the invention shown here, sensor surfaces  355  of stator  250  are configured and/or arranged to intermesh with each other in the plane of extension of stator  250 . In other words, the spaces between sensor surfaces  355  exhibit an angular or zigzag pattern. The plane of extension of stator  250  corresponds to the plane of the drawing of  FIG. 3 . 
       FIG. 4  schematically shows a rotor  260  of a device or detecting device according to an exemplary embodiment of the present invention. Rotor  260  is, for example, the rotor of  FIG. 2  or a similar rotor. The view of  FIG. 4  shows electrically conductive section  462  and dielectric non-conductive section  464  of rotor  260 . As can be seen, conductive section  462  is larger in area than non-conductive section  464 . 
       FIG. 5  schematically shows a device  240  or detecting device  240  according to an exemplary embodiment of the present invention. Detecting device  240  corresponds or is similar to the detecting device of  FIG. 2 . Rotor  260  of detecting device  240  corresponds or is similar to the rotor of  FIG. 4 . For purposes of illustration, only the conductive section of rotor  260  is shown in  FIG. 5 . Rotor  260  may also be referred to as inverted rotor  260 . The stator of detecting device  240  is similar to the stator of  FIG. 3 ; i.e., corresponds to the stator of  FIG. 3 , except that, for purposes of illustration,  FIG. 5  shows only four sensor surfaces  355  of the stator, which do not have an intermeshing configuration. 
     In  FIG. 5 , it can be seen that the conductive section of rotor  260  is configured to cover more than one sensor surface  355  of the stator. In accordance with the exemplary embodiment of the present invention shown in  FIG. 5 , the conductive section of rotor  260  is configured to cover more than two sensor surfaces  355  of the stator. Further, in  FIG. 5 , a sensor surface  355  to be currently measured is represented by single hatching, while the sensor surfaces  355  surrounding the sensor surface  355  to be measured are represented by cross-hatching. 
       FIG. 5  illustrates a measuring principle where all sensor surfaces  355  are sequentially or periodically measured for their capacitance. A covered sensor surface  355  is understood to mean a sensor surface  355  of the stator that is covered by the copper surface or the conductive section of rotor  260 . An uncovered sensor surface  355  is understood to mean a sensor surface  355  of the stator that is covered by an open area or the non-conductive section of rotor  260 ; i.e., which is not covered by the copper surface. A sensor surface  355  to be measured or being scanned is understood to mean a sensor surface  355  of the stator that is being measured or scanned by the controller or microcontroller at this point in time. During a complete scanning operation, all sensor surfaces  355  are measured sequentially; i.e., bit by bit. During such a measurement, it can be detected whether a sensor surface  355  is or is not covered by rotor  260 . In this connection, a covered sensor surface  355  is referred to as inactive, while an uncovered sensor surface  355  is referred to as active. In the snapshot view of  FIG. 5 , the measurement would show that the sensor surface to be measured or being scanned is covered by rotor  260 , and thus is inactive. In the sequential or periodic capacitance measurement of all sensor surfaces  355 , a high capacitance delta means a covered and thus inactive sensor surface  355 , while a low capacitance delta means an uncovered and thus active sensor surface  355 . 
       FIG. 6  shows a flow chart of a determination method  600  according to an exemplary embodiment of the present invention. Determination method  600  is executable to determine a rotational position of a rotatable element. The rotatable element is coupled to the rotor of the device of  FIG. 2  or  FIG. 5 , or to that of a similar device. Thus, determination method  600  is executable in connection with the device of  FIG. 2  or  FIG. 5 , or a similar device. Determination method  600  is further executable by or using the controller of  FIG. 2  or a similar controller. 
     Determination method  600  includes a step  610  of performing a first series of measurements, during which an electrical measuring potential is applied to all sensor surfaces of the stator. Also in this step, reference signals are read from the sensor surfaces of the stator in response to the applied measuring potential. The reference signals represent first capacitance values of the sensor surfaces, which are dependent on a position of the rotor. 
     Determination method  600  further includes a step  620  of executing a second series of measurements. In this step, the electrical measuring potential is applied to one sensor surface to be measured among the sensor surfaces, and an electrical ground potential is applied to all other sensor surfaces. In step  620  of executing the second series of measurements, each of the sensor surfaces is sequentially traversed as a sensor surface to be measured. Then, measurement signals are read from the sensor surfaces in response to the applied measuring potential and the applied ground potential. The measurement signals represent second capacitance values of the sensor surfaces, which are dependent on a position of the rotor. 
     Following the step  610  of performing the first series of measurements and the step  620  of executing the second series of measurements, useful signals are generated in a generating step  630  based on the reference signals and the measurement signal. In a subsequent processing step  640  of method  600 , the useful signals are processed to determine the rotational position of the rotatable element. 
       FIG. 7  shows a flow chart of a position determination process  700  according to an exemplary embodiment of the present invention. In other words,  FIG. 7  illustrates a program sequence of position determination process  700 . Position determination process  700  is executable in connection with the determination method of  FIG. 6  or a similar method, and in connection with the sensor system of  FIG. 2  or a similar sensor system. 
     Position determination process  700  starts at a block  702 . Then, an initialization is performed at a block  704 . Subsequently, at a block  706 , all sensor surfaces are set to shield or to the measuring potential. Then, at a block  708 , all sensors or sensor surfaces are scanned. Subsequently, in a block  710 , a baseline is set to a measured raw count value. Subsequently, in a block  712 , all sensor surfaces are set to ground (GND); i.e., to the ground potential. Then, in a block  714 , all sensors or sensor surfaces are scanned. In a block  716 , the useful signals or signals are then equalized and a separate baseline is calculated. Subsequently, in a block  718 , the useful signal or signal is inverted and normalized and/or equalized. Finally, in a block  720 , signal evaluation is performed using a weighting calculation. Once the signal evaluation is complete, the program sequence of position determination process  700  may return to block  706 . 
       FIG. 8  shows a schematic signal waveform diagram according to an exemplary embodiment of the present invention. The signal waveform diagram is to be considered in connection with the sensor system of  FIG. 2  or a similar sensor system and/or in connection with the determination method of  FIG. 6  or a similar method, in particular in connection with the processing device of the controller of the sensor system. 
     A rotational angle of the rotatable element or rotor relative to the stator of the detecting device of the sensor system is plotted on the axis of abscissas  802  of the signal waveform diagram over a range of 0 to 360 degrees. Signal values are plotted on the axis of ordinates  804  of the signal waveform diagram. In the signal waveform diagram, by way of example, waveforms of only four acquired or generated useful signals  810 ,  820 ,  830  and  840  are plotted as a function of the rotational angle. 
       FIG. 9  shows a schematic signal waveform diagram according to an exemplary embodiment of the present invention. The signal waveform diagram shown in  FIG. 9  corresponds to that of  FIG. 8  with the exception that  FIG. 9  shows useful signals  810 ,  820 ,  830  and  840  in equalized form. 
       FIG. 10  shows a schematic signal waveform diagram according to an exemplary embodiment of the present invention. The signal waveform diagram shown in  FIG. 10  corresponds to that of  FIG. 9 , except that in  FIG. 10 , useful signals  810 ,  820 ,  830  and  840  are, in addition, shown in normalized and inverted form. 
     With reference to  FIGS. 1 through 10 , exemplary embodiments of the present invention will hereinafter be described in summary and/or explained once again using different words. Important aspects of exemplary embodiments include a geometry of rotor  260  and stator  250 , as well as a sequence of method  600  with respect to the measurement and evaluation of capacitances. 
     A potential difference necessary for such a measurement is coupled in via rotor  260 ; i.e., via its conductive section  462 , which couples the potential difference in via the sensor surfaces  355  that are adjacent a sensor surface  355  being measured, as shown in  FIG. 5 . To this end, sensor surfaces  355  may be configured for the unscanned state, for example, in a software of controller or microcontroller  270 . In such a measurement method, there is provided a rotor  260  having a conductive section  462  or an electrically conductive surface of at least two sensor surfaces  355 . Thus, a useful signal  286 , or  810 ,  820 ,  830  or  840 , respectively, does not experience a low point while a sensor surface  355  is being traversed, because no reduction occurs in the coupled-in area of the surrounding sensor surfaces  355 , and a high raw value can be obtained using such an inverted rotor  260 , such as is shown in  FIG. 4 . In an inverted rotor  260 , conductive section  462  (i.e., the copper surface) and non-conductive section  464  (i.e., the open area) of rotor  260  are interchanged, as compared with a conventional rotor. An inverted rotor  260  features a conductive section  462  that occupies more than 180 degrees of rotor  260 . In an inverted rotor  260 , an active sensor surface  355  is not covered and an inactive sensor surface  355  is covered by conductive section  462 . For this reason, useful signals  286 , or  810 ,  820 ,  830  or  840 , respectively, are inverted computationally. 
     In order to computationally remove environmental influences and interferences and to maintain operation after a restart of sensor system  230 , the first series of measurements is performed as a reference measurement. This is done by a performing a measurement with the surrounding sensor surfaces  355  configured to shield. In this measurement, the surrounding sensor surfaces  355  are charged to the potential of the sensor surface  355  to be measured, and thus a rotor  260  which is coupled-in and one which is not coupled-in will measure nearly the same raw value across all sensor surfaces  355 . The first series of measurements serves as a reference. Subsequent to the first series of measurements or measurement with the surrounding sensor surfaces  355  configured to shield, the second series of measurements is performed with the surrounding sensor surfaces  355  configured to ground. The difference between the measurement at ground and the measurement at shield represents the useful signal  286 , or  810 ,  820 ,  830  or  840 , respectively, as shown in  FIG. 8 . To be able to compare useful signals  286 , or  810 ,  820 ,  830  and  840 , respectively, to each other, the ratios of useful signal  286 , or  810 ,  820 ,  830  or  840 , respectively, relative to one another are included and designated as rotational angle sensor parameters. These ratios are used to equalize useful signals  286 , or  810 ,  820 ,  830  and  840 , respectively, based on percentages, as shown in  FIG. 9 . Because of inverted rotor  260 , useful signals  286 , or  810 ,  820 ,  830  and  840 , respectively, are inverted and, for the sake of better illustration, normalized via the ratio between active and inactive sensor surfaces  355 , for example, to many, for example 1000, values, as shown in  FIG. 10 . 
     For purposes of determining the rotational or angular position, the equalized and inverted useful signals  286 , or  810 ,  820 ,  830  and  840 , respectively, are converted to a defined resolution by the weighting calculation. For the weighting calculation, it is desired, for example, that intersection points between rising and falling useful signals  286 , or  810 ,  820 ,  830  and  840 , respectively, are located at about 75 percent of a maximum signal value. For this reason, sensor surfaces  355  intermesh with each other, as shown in  FIG. 3 , whereby each individual sensor surface  355  is covered earlier by rotor  260  as the rotor is rotated thereover, thus raising the intersection point of falling and decreasing useful signals  286 , or  810 ,  820 ,  830  and  840 , respectively. 
     For a more accurate position determination, corridors are defined within the weighted value for a position. If the value of a useful signal  286 , or  810 ,  820 ,  830  or  840 , respectively, is within such a corridor, then an associated detent position of rotatable element  120  is recognized. If the value is outside the corridor, the previous position is maintained. This prevents jumping between two positions. 
     In other words, in order to detect the rotational position, it is necessary to measure the capacitance of each sensor surface  355 . Two extreme cases can be distinguished: a covered, scanned sensor surface  355  on the one hand, and an uncovered, scanned sensor surface  355  on the other hand. In the case of the covered sensor surface  355 , a potential difference can be coupled in via rotor  260 . Thus, a higher capacitance is measured compared to an uncovered sensor surface  355 . 
     In order for determination method  600  or the measurement method to be absolute and independent of external interference effects, the first series of measurements; i.e., a reference measurement of an individual sensor surface  355 , is performed with the surrounding sensor surfaces  355  configured to shield. In this configuration, a low capacitance is measured because all sensor surfaces  355  are at the same potential and, therefore, cannot be coupled in via rotor  260 . Thus, the measurement of all sensor surfaces  355  (regardless of whether covered or uncovered) may yield a similar measurement value temporally and between the sensor surfaces  355 . The first series of measurements (i.e., a reference measurement) is performed with each individual sensor surface  355  of stator  250  prior to executing the second series of measurements or a further measurement. The measurement values are stored, for example, in an array in a program of controller  270 . 
     Despite the efforts to make the individual sensor surfaces  355  as equal as possible, differences may occur, which may affect the useful signals  286 , or  810 ,  820 ,  830  and  840 , respectively, of the individual sensor surfaces  355 . To nevertheless be able to compare useful signals  286 , or  810 ,  820 ,  830  and  840 , respectively, relativities have been included. To this end, for example, a ratio of a maximum signal value of a sensor surface to a maximum signal value of a reference sensor was included. A reference sensor may be any of the sensor surfaces  355  disposed on stator  250 . This relativities are used to equalize useful signals  286 , or  810 ,  820 ,  830  and  840 , respectively. 
     After the first series of measurements, or reference measurement, all sensor surfaces  355  are scanned once again. During this, the potential of the sensor surfaces  355  surrounding a respective sensor surface  355  being scanned is at ground. In the second series of measurements, a high capacitance is measured for a covered sensor surface  355 , and a low capacitance is measured for an uncovered sensor surface  355 . The measured capacitance is stored, for example, in another array in the program of controller  270 . 
     A difference is calculated from the series of measurements; i.e., from the reference measurement, and the ground measurement, and thus the individual sensor signals are comparable to each other. In addition, this calculation eliminates interference effects (caused, for example, by a hand). Moreover, the reference measurement actually performed in the first series of measurements allows useful signals  286 , or  810 ,  820 ,  830  and  840 , respectively, to remain comparable to previous values, even after a restart of controller  270 . 
     Through the use of inverted rotor  260 , useful signals  286 , or  810 ,  820 ,  830  and  840 , respectively, of sensor surfaces  355  are then inverted to be able to perform an equilibrium calculation. In addition, the signal level of each useful signal  286 , or  810 ,  820 ,  830  and  840 , respectively, is not fully identical to the other sensors, so that an additional ratio is included which describes a percentage ratio between a high point and a low point of a useful signals  286 , or  810 ,  820 ,  830  or  840 , respectively. Both operations (inversion and normalization) are performed, for example, in processing step  640 . Normalized and inverted useful signals  286 , or  810 ,  820 ,  830  and  840 , respectively, are shown, for example, in  FIG. 10 . 
     At a preliminary stage, a resolution is defined for rotatable element  120  or the rotary selector switch. The position or rotational position can then be calculated, within the resolution, from the normalized and inverted useful signals  286 , or  810 ,  820 ,  830  and  840 , respectively, using the weighting calculation. In order to define the resolution, the level of useful signals  286 , or  810 ,  820 ,  830  and  840 , respectively, is considered at a preliminary stage. Moreover, an intersection point of two signals may be located at 75 percent of the maximum signal. The weighting calculation considers the sensor surface  355  having the greatest signal. Since the arrangement of the sensor surfaces on stator  250  is known, a corridor of the rotational position may already be determined via the highest signal of useful signals  286 , or  810 ,  820 ,  830  and  840 , respectively. Subsequently, the rotational position can be inferred more accurately via the sensor surfaces  355  adjacent the sensor surface  355  having the highest signal. 
     The rotational position calculated from the equilibrating calculation is then converted to the desired number of positions. The desired number of positions is calculated using, for example, a divisor and a modulo operator. To this end, initially, a corridor is defined in which each rotational position or detent position is located. The use of a corridor has the advantage that the position is reliably detected and does not jump. The corridors also make it possible to detect whether a detent mechanism is located, and thus stuck, between two positions. A number of detent position of rotatable element  120  is selectable within the resolution within wide limits or almost freely. 
     The position, rotational position or detent position of rotatable element  120  or of the rotary selector switch is known at this point and can be further processed by controller  270  or. Thereafter, the program sequence for capacitance-based contactless and absolute determination of rotational angles restarts from the beginning with performing the first series of measurements on sensor surfaces  355 , as shown, for example, in  FIG. 7 . 
     By converting the resolution to detent positions of rotatable element  120 , it is further possible to freely select an initial detent position on rotatable element  120  or the rotary selector switch at any time during, for example, the development or manufacture, or after delivery. 
     Based on useful signals  286 , or  810 ,  820 ,  830  and  840 , respectively, a weighting calculation function of controller  270  may calculate, for example, a so-called radial slider having a defined resolution. The individual desired detent positions may be calculated from this resolution. This is possible within a range of, merely by way of example, 2 to 13 detent positions using the existing sensor surfaces  355 . This does not require any change in hardware, but only an adaptation of the software. Advantageously, it is only necessary to configure the sensors and, in a manufacturing process, it is only required to install the appropriate detent mechanism. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below. Additionally, statements made herein characterizing the invention refer to an embodiment of the invention and not necessarily all embodiments. 
     The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and/or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.