WO2006131276A1

WO2006131276A1 - Capacitive sensor for measuring a measurable variable

Info

Publication number: WO2006131276A1
Application number: PCT/EP2006/005293
Authority: WO
Inventors: Heinz KÜCK; Daniel Warkentin; Daniel Benz; Tim Botzelmann
Original assignee: Hahn-Schickard-Gesellschaft für angewandte Forschung e.V.
Priority date: 2005-06-06
Filing date: 2006-06-02
Publication date: 2006-12-14
Also published as: DE102005025908B3; EP1896795A1

Abstract

Disclosed is a sensor for measuring a measurable variable. Said sensor comprises a first couple of electrodes (103) and a second couple of electrodes (105). The electrodes (103a, 103b, 105a, 105b) of the first couple of electrodes (103) and the second couple of electrodes (105) are alternately electrically disconnected from each other and interconnected in a conductive manner. A capacity measuring device (111, 113) can then determine a first and a second measured differential capacity value such that a processing device (117) can determine a measured value with the aid of the first measured differential capacity value and the second measured differential capacity value.

Description

Capacitive sensor for measuring a measured variable

description

The present invention relates to a capacitive sensor for measuring a measurand.

In general, capacitive sensors can be used for a variety of household, industrial and research applications. Examples include inclination sensors, which can be used as rollover sensors in motor vehicles, as monitoring sensors of alarm systems in vehicles and buildings and as position sensors for automated machines, irons, washing machines, etc.

A number of conventional sensors are used to measure a measured variable capacitance difference of a capacitor arrangement, a measured variable, such. As the inclination with respect to the horizontal surface or the horizontal to determine.

For this purpose, for example, inclination sensors are used, which determine the slope via a measurement of a differential capacitance in case of change due to inclination of the covered area of a differential capacitor arrangement formed with an electrically conductive pendulum. Further capacitive sensors perform a differential capacitance measurement, whereby a change in the inclination of an arrangement of an electrically conductive liquid with respect to the capacitor electrodes partially covered by it is determined.

In addition, conventional capacitance sensors are used to detect the rotation angle of a shaft by means of a measurement of an angle-dependent differential capacitance of a differential capacitor arrangement. there The differential capacitor arrangement can be realized via an electrically conductive disk connected to the shaft.

DE4141324A1 shows a capacitive tilt sensor which has a hollow body or a cylindrical container. On one or both end surfaces of the container insulating plates are arranged, on which preferably two separate semicircular metal coatings are arranged. The cavity of the container is preferably filled halfway with a liquid having a relatively high dielectric constant. Two opposing metal pads each form together with the liquid a capacitor, wherein the individual capacitors are designed as differential capacitor arrangements. If the container is tilted, the liquid will remain on a horizontal liquid level due to the gravitational force. This results in a slope-dependent change in the area covered by the liquid surface of the metal coverings.

DE10007246A1 discloses an electrostatic capacitive tilt sensor in which a pair of semicircular differential electrodes are arranged side by side in the vertical direction. As a result of this arrangement of the electrodes, the capacitance difference of the differential capacitor arrangement becomes maximum in the horizontal position of the sensor. In a downstream electronics, which processes a signal coming from the sensor, therefore, a zero point adjustment and temperature compensation is no longer necessary.

DE3512983A1 teaches a capacitive tilt and flatness meter which has a hermetically sealed housing which is preferably filled up to one-half with a dielectric nonconductive fluid. Four circular-segment-shaped electrodes which form a capacitor arrangement are immersed in the liquid. If the is tilted from its reference position, the immersion depth of the electrodes in the dielectric liquid changes, whereby the capacitances of the capacitor arrangement change depending on the inclination of the measuring device.

In DE10217859C1 a capacitive tilt sensor is shown, in which a pair of semicircular electrodes are arranged in the horizontal direction next to one another and face a common electrode. Between the opposing electrodes is a semi-circular pendulum of electrically conductive material, which has a very small distance from the housing electrodes, so that there is a differential capacitor arrangement. Upon rotation of the housing relative to the horizontal, the overlap between the pendulum and the first part electrode increases, while at the same time the overlap between the pendulum and the second part electrode decreases, which is why the capacitances of the two capacitors change in opposite directions and a slope-dependent measurable capacitance difference arises.

Fig. 7 shows a conventional capacitance sensor 10 for measuring a slope in a plan view. The conventional capacitance sensor 10 has a housing which consists of a first housing wall 11 and a second housing wall 13. In the second housing wall 13 is a cavity or cavity, which is cylindrical here, introduced.

On a surface 15 of the cavity are a first capacitor electrode 17a and a second capacitor electrode 17b. On a surface 18 of the first housing wall 11, a common capacitor electrode 19 is applied. In the cavity, a liquid 21, often a dielectric liquid 21, is interposed between the first capacitor electrode 17a, the second capacitor electrode 17b and the common capacitor electrode 19. The conventional capacitance sensor 10 rotates about a rotation axis 23. An electrical circuit 25 is applied to a surface of the first housing wall 13 facing away from the common capacitor electrode 19.

The first capacitor electrode 17a forms a first capacitor with the common capacitor electrode 19, and the second capacitor electrode 17b forms a second capacitor with the common capacitor electrode 19. The electric circuit 25 detects the difference between the capacitance of the first capacitor and the second capacitor.

The closed or sealed Kavitat is preferably filled up to half with the dielectric liquid 21, such as. As a silicone oil, wherein the dielectric fluid due to the gravitational field aligns so that their liquid level is always horizontal.

When the housing of the conventional capacitance sensor 10 tilts around the rotation axis 23, the dielectric liquid 21 remains at a horizontal liquid level. Thus, the area ratios of the first capacitor electrode 17a covered by the dielectric liquid 17a and the second capacitor electrode 17b change, which also change the capacitances of the first capacitor and the second capacitor.

An arrow 26 shows a direction of rotation of the sensor to the right or clockwise. When the conventional capacitance sensor 10 is rotated to the right, a area of the first capacitor electrode 17a covered by the dielectric liquid 21 decreases, while a area of the second capacitor electrode 17b covered by the dielectric liquid 21 increases. Thus, the capacitance of the first capacitor decreases, while the capacitance of the second capacitor increases. When the housing of the conventional capacitance sensor 10 is rotated leftward, the capacitance of the first capacitor increases while that of the second capacitor decreases. Thus, by determining the capacitance of the first capacitor and the second capacitor, the direction of rotation can be detected.

The conventional capacitance sensor 10 thus determines the inclination or rotation of the housing relative to a gravitational field around the rotation axis 23 by means of a capacitance change of the first and second capacitors caused by a change in the arrangement of the charged liquid 21 becomes. As a result of the tilting of the dielectric liquid 21, the overlap of the liquid-covered surfaces of the electrodes 17a, 17b and 19 which face one another is changed, and this change is read capacitively.

In Fig. 8, the formation of the first capacitor 27a, which is provided with the reference numeral 27a in Fig. 8, and the second capacitor 27b, which is provided with the reference numeral 27b in Fig. 8, is schematically explained. As explained above, the first capacitor 27a forms between the first capacitor electrode 17a and the common capacitor electrode 19, while the second capacitor 27b is formed between the second capacitor electrode 17b and the common capacitor electrode 19.

In order to obtain a continuous analog output signal which depends on an absolute slope of the conventional capacitance sensor 10 with respect to the horizontal, the first capacitor 27a and the second capacitor 27b are connected together in a differential capacitor arrangement. With an inclination of the housing of the conventional capacitance sensor 10 with respect to the dielectric liquid 21, which remains in the horizontal, the capacitances of the first capacitor 27a and the second change Capacitor 27b opposite to each other. From the capacitor basic equation, the following equation for determining the basic capacitance Co can thus be determined for the conventional capacitance sensor 10 shown in FIGS. 7 and 8 with semicircular capacitor electrodes 17a, 17b arranged horizontally next to each other.

p ^c 0 ( ^v p ^c -r air 4

-

In the above formula for the basic capacitance Co is the electric field constant, ε is _rair ε _{0 is} the dielectric constant of air and ε _rd i _e _t iek r.Fi. the dielectric constant of the dielectric liquid, A the area of a partial electrode covered by the air or silicon, and d the distance of the partial electrodes from the common electrode. To increase the measuring sensitivity of the conventional sensor 10, the difference of the first capacitance 27a and the second capacitance 27b is determined in the circuit 25 and converted into a voltage. The relationship for the differential capacitance for the conventional capacitance sensor 10 for measuring an inclination shown in FIG. 7 is given by the following formula:

_ ₂ _ΔA (α), ₎

In the above formula, ΔA (α) is the inclination angle α-dependent change in the area of the differential capacitor array covered with the dielectric liquid 21, which includes the first capacitor 27a and the second capacitor 27b. The resolution of the conventional sensor 10 is dependent on the smallest measurable capacity of the electronics used, in this case the electric circuit 25, and results from the equation below: _ min_ min _ raax max α

α _min is hereby the smallest angle to be resolved, ΔC _ma χ _α the difference capacitance at the completely exhausted measuring range Oj _{13x of} the conventional sensor 10 and C _m i _n the minimum detectable capacitance change of the electronics.

FIG. 9 shows a conventional evaluation circuit 51 which serves to generate an output signal of the conventional capacitance sensor 10. In the conventional evaluation circuit 51, a signal generator 53 for generating a carrier signal is connected via the first capacitor 27a to a first charge amplifier 55a and via the second capacitor 27b to a second charge amplifier 55b. The first charge amplifier 55a is implemented as a known operational amplifier circuit comprising a first operational amplifier 55al, a capacitor 55a2 and an ohmic resistor 55a3, which are connected together as shown in FIG. The second charge amplifier 55b, like the first charge amplifier, is implemented as a known operational amplifier circuit, and has a second operational amplifier 55bl, a second capacitor 55b2, and a second ohmic resistor 55b3, which are connected together as shown in FIG.

An output signal of the first charge amplifier 55a and the second charge amplifier 55b are respectively supplied to a known demodulator circuit 57. The demodulator has a first demodulator diode 57al, a first demodulator resistor 57a2, a first demodulator capacitor 57a3, a second demodulator diode 57bl, a second demodulator resistor 57b2, and a second demodulator capacitor 57b3. The elements of the demodulator 57 are interconnected as shown in FIG. The demodulator 57 generates in dependence on the signal supplied by the first charge amplifier 55a has a first output signal and a second output signal in response to a signal supplied by the second charge amplifier 55b, the first and second output signals being fed to a known differential amplifier 59 or instrumentation amplifier OP become. The differential amplifier 59 has a differential amplifier operational amplifier 59a and a differential amplifier resistor 59b, which are interconnected as shown in FIG.

A terminal of the signal generator 53, a terminal of the first operational amplifier 55al and the second operational amplifier 55bl, and a terminal of the demodulator 57 are connected to a ground terminal.

The differential amplifier 59 generates a sensor output signal applied to an output terminal 61. The magnitude of the measurement signal or sensor output signal present at the output terminal 61 and its sign are dependent on a difference between the capacitance of the first capacitor 27a and the second capacitor 27b.

A disadvantage of the conventional capacitance sensor 10 shown in FIG. 7, which is read out with the conventional evaluation circuit 51 shown in FIG. 9, is that with a very large difference between the capacitance of the first capacitor 27a and the capacitance of the second capacitor 27b, coupled interference easily superimposed on the measurement signal of the evaluation circuit, which is applied to the output terminal 61. This very large difference between the capacitance of the first capacitor 27a and the second capacitor 27b occurs, for example, with a very large coverage of the first capacitor electrode 17a with the dielectric liquid 21 and a very low coverage of the second capacitor electrode 17b. Another disadvantage is that in the conventional capacitance sensor 10, a non-optimal filling volume of the liquid 21 has a very strong effect on the sensor characteristic. In this case, the change of the capacitances of the first capacitor electrode 17a to the capacitance of the second capacitor electrode is particularly in the edge regions of the characteristic of the sensor in which the first capacitor electrode 17a or the second capacitor electrode 17b is often covered to a high percentage by the liquid 21 17b is very low, which is why the sensitivity of the sensor is greatly reduced in these areas.

A further disadvantage of the conventional capacitance sensor 10 shown in FIG. 7 is that due to the arrangement of the capacitor electrodes 17a, 17b, 19, only angles in a range of -90 ° to 90 ° can be clearly detected. If, in the above embodiment, the angle of rotation z. B. has a value of -90 ° or 90 °, the difference of the capacitances of the first capacitor 27a and the second capacitor 27b is maximum.

If z. For example, if the rotation angle by which the conventional sensor 10 shown in FIG. 7 is inclined exceeds 90 ° and falls below -90 °, a change in the difference in capacitance between the first capacitor 27a and the first capacitor 27a is second capacitor 27b independent of the direction of rotation of the conventional capacitance sensor 10. In other words, z. For example, the value of the difference in capacitance between the first capacitor 27a and the second capacitor 27b at an inclination angle of 80 ° (80 ° = 90 ° -10 °) is exactly as high as an inclination angle of 100 ° (100 ° = 90 ° + 10 °).

Thus, with the conventional capacitance sensor shown in FIG. 7, an unambiguous determination of the angle of rotation is possible only in a range of -90 ° to 90 °. Fig. 10 explains a structure of another conventional capacitance sensor 80. In the following description of the other conventional capacitance sensor 80 shown in Fig. 10, the same or the same elements are given the same reference numerals. In particular, elements that are the same or equivalent to those of FIG. 7 are given the same reference numerals, and the following description is limited to the illustration of the differences from the structure of FIG. 7.

In contrast to the conventional capacitance sensor 10 shown in FIG. 7, the other conventional capacitance sensor 80 includes a third capacitor electrode 81 a, a fourth capacitor electrode 81 b, and another common capacitor electrode 83. The third capacitor electrode 81a and the fourth capacitor electrode 81b form a pair of annular electrodes and surround the first capacitor electrode 17a and the second capacitor electrode 17b. The third capacitor electrode 81a and the fourth capacitor electrode 81b are arranged at an angle of 90 ° to the first capacitor electrode 17a and the second capacitor electrode 17b. However, the third 81a and the fourth 81b electrodes could be arranged rotated by any angle in a range of 0 to 180 ° with respect to the first capacitor electrode 27a and the second capacitor electrode 27b.

In addition to the conventional capacitance sensor 10 shown in FIG. 7, the third capacitor electrode 81a and the other common electrode 83 constitute a third capacitor, and the fourth capacitor electrode 81b and the other common electrode 83 form a fourth capacitor. Thus, the other conventional capacitance sensor 80 has four capacitors whose capacitance depends on a slope of the other conventional capacitance sensor 80.

FIG. 11 explains an equivalent circuit diagram of the other conventional capacitance sensor 80 shown in FIG The first differential capacitance 87 results from the different capacitances of the first capacitor 27a and the second capacitor 27b. At the same time, a second differential capacity 89 results from a difference in the capacitances of the third capacitor and the fourth capacitor.

The other conventional capacitance sensor 80 makes it possible to measure rotation angles in a range of -180 ° to 180 °.

A disadvantage of the further conventional capacitance sensor 80 shown in FIG. 10 is that the arrangement of the third capacitor electrode 81a and the fourth capacitor electrode 81b on a circular ring around the first capacitor electrode 17a and the second capacitor electrode 17b increases the space required for the further conventional one Capacitance sensor 80 results.

This increased space requirement makes the further conventional capacitance sensor 80 more difficult to integrate in technical devices. In addition, a larger housing is required to accommodate the other conventional capacitance sensor 80, so that the material consumption increases. This increases the manufacturing cost of the other conventional capacitance sensor.

A disadvantage of the further conventional capacitance sensor shown in FIG. 10 is also the different shape of the capacitor electrodes 17a, 17b, the capacitor electrodes 81a, 81b, the common capacitor electrode 19 and the further common capacitor electrode 83. Thus, for the further conventional capacitor shown in FIG Capacitance sensor 80 a number of different shaped capacitor electrodes are provided for its production. This makes it difficult to store the components and at the same time leads to an increase in production costs. The De 3711062 C2 shows a block diagram of a measuring device with a capacitive sensor. A reference voltage source, which provides two reference voltage potentials, is connected to reference plate pairs on stator plates using a reference potential switch such that two horizontally adjacent or two vertically adjacent sectors alternately appear to be connected together and form a 180 ° sector. A position of sensor electrodes relative to the reference potential electrodes or an overlap of the sensor electrodes with the reference potential electrodes is dependent on a position or a rotational angle α of a rotor on which the sensor is mounted with the sensor electrodes.

Between the two stator plates with the reference potential electrodes, the circular sensor is arranged, on which two sensor electrodes are respectively arranged on one of the first stator plate and one of the second stator plate facing surface. Via a coupling electrode region of the sensor electrodes, the sensor voltage is coupled out from the sensor electrodes to the coupling electrode surfaces arranged on the stator plates. The high-impedance voltage generated on the coupling electrodes is then decoupled via a fast charge amplifier in an evaluation circuit.

DE 1996089 A1 shows a capacitive tilt sensor which has a hollow body with surface electrodes arranged on outer surfaces. The interior of the hollow body is partly filled with an electrically ^'conductive liquid. The surface electrodes form with the electrically conductive liquid in the interior of the hollow body plate capacitors, which are connected in a capacitive star connection, wherein the capacitances of Plattenkondensato ^¬ ren adjusted according to the liquid level at the respective surface electrode of the hollow body. An evaluation circuit that records the capacities of the plate capacitors. In the evaluation circuit, a square-wave AC voltage is applied via the switches optionally to a series connection of the first and the second capacitors or

a series connection of the first capacitor and the third capacitor is applied.

At the same time, the voltage at the node is coupled out via the remaining capacitance, that is to say the capacitance which is not connected in each case in the series connection of the capacitors, and fed to a subsequent preamplifier. Thus, a difference in the capacitances of the first and second capacitors and a difference in the capacitances of the first and third capacitors is determined.

EP 1396703 A2 teaches a capacitive angular position sensor. The capacitance sensor has a rotor disposed between electrodes on plates, wherein the capacitance between the electrodes varies depending on a position of the rotor. In this case, two transmitter electrodes are arranged on a transmitter plate, while four receiver electrodes are arranged on a receiver plate. Two receiver electrodes are electrically conductively connected via a conductor, while two further receiver electrodes are electrically conductively connected to one another via a further conductor. A microcontroller drives an analog switch to alternately evaluate a signal supplied from the receiver electrode pair having two interconnected receiver electrodes and a signal supplied from the further receiver electrode pair having two further receiver electrodes, and an absolute value of the angular position by means of a look-up table in FIG Microcontroller is determined.

U.S. Patent 5,172,481 shows a sensor for determining a slope having a housing. On the case are disposed on a surface of electrodes A, B, and on a surface of the housing opposite to the electrodes A, B, electrodes C, D, so that the electrodes A, B overlap with the two electrodes C, D, respectively, and the electrodes C, D overlap with the electrodes A, B, respectively. The electrodes A, B and C, D are each separated by a recess 8, so that they are not in direct electrical contact with each other. In the housing, a conductive liquid is arranged, which partially fills a cavity arranged in the housing. Depending on an inclination of the sensor, either the electrodes A, B are connected together so that they form a common electrode, while the electrodes C, D act as sensor electrodes, or the electrodes C, D are connected together, so that they have a common Form electrode, while the electrodes A, B act as sensor electrodes. When the electrodes C, D are connected together, a resistance between the electrodes C, D and the electrode A and a resistance between the electrodes C, D and the electrode B are determined, the resistance being of a degree in which the electrodes A or B are immersed in the liquid depends. Thus, a resistance Zl of a path between the electrodes C, D and the electrode A and a resistance Z2 of a path between the electrodes C, D and the electrode B is detected. From a ratio R of the resistors Zl, Z2 to each other, an inclination angle is determined.

The object of the present invention is to provide a sensor for measuring a measured variable, which is improved in its space requirement and is cheaper to manufacture. This problem is solved by the newly presented claim 1.

The present invention provides a sensor for measuring a measured variable with a first electrode pair having a first electrode and a second electrode, a second electrode pair having a third electrode and a fourth electrode, wherein between the first electrode pair and the second electrode pair, a gap is formed, and wherein the electrodes of the first and the second pair of electrodes are arranged such that one electrode of an electrode pair overlaps with the two electrodes of the other pair of electrodes, a movable element whose position relative to the first and the second pair of electrodes depends on the measured variable, and between the first electrode pair and the second electrode pair is arranged, a capacitance measuring device for measuring a first differential capacitance between a first sub-capacitor, which by the first electrode pair, in which the first and the second electrode are conductively connected to each other u and the third electrode is formed, and a second sub-capacitor formed by the first electrode pair and the fourth electrode, and for measuring a second differential capacitance between a third sub-capacitor passing through the second electrode pair, wherein the third and fourth electrodes are conductive and a first sub-capacitor formed by the second electrode pair and the second electrode and processing means for generating a measured value for the measured quantity using the first differential capacitance and the second differential capacitance.

The present invention is based on the finding that, in the case of a sensor for measuring a measured variable which has two electrode pairs, the first and the second electrode of the first electrode pair can alternately be conductively connected to one another, and the third and Fourth electrode of the second pair of electrodes can be conductively connected together. In this case, a movable element is arranged between the two electrode pairs whose position changes in dependence on a measured variable, so that in each case the capacitance between the electrodes and the opposite electrode pair changes depending on the position of the movable element.

A capacitance measuring device can then have a first differential capacitance between a first partial capacitor, which is formed by the first electrode pair, in which the first and the second electrode are conductively connected to each other and the third electrode, and a second Teilkon- capacitor, by the first pair of electrodes and the fourth electrode is formed, and a second differential capacitance between a third sub-capacitor formed by the second electrode pair, in which the third and fourth electrodes are conductively connected to each other and the first electrode is formed, and a fourth sub-capacitor formed by the second electrode pair and the second electrode is formed determine. In a downstream processing device, a measured value can then be determined using the first differential capacitance and the second differential capacitance.

Thus, in a sensor according to an embodiment of the present invention for measuring a measured quantity, only two pairs of electrodes are to be arranged opposite one another. In this case, the area of an additional pair of electrodes can be saved as a common electrode by the respective combined use of two electrodes or partial electrodes of a pair of electrodes, so that the size of the sensor is thereby reduced. This results in a smaller space requirement than in the other conventional capacitance sensor. Thus, the sensor for measuring a variable is easier and more flexible integrated in a small space in an electrical device. In addition, the reduced space requirement leads to a lower material consumption for the components of the sensor, such. B. the housing. Thus, the sensor can be manufactured more cheaply.

In addition, in the sensor for measuring a measured quantity, all the electrodes in one embodiment of the present invention may have the same shape, resulting in a reduction in component variety. This reduction in the variety of components leads to a simpler storage of the components and thus to lower manufacturing costs.

A further advantage results in one embodiment of the present invention in that deviations from an optimum fill level in a sensor in which the movable element is a liquid have a smaller influence on the measurement signal, since in each case one of the two differential capacitance Arrangements not an electrode is completely covered, and thus the influence of the level height is lower.

Preferred embodiments of the present invention will be explained in more detail below with reference to the accompanying drawings. Show it:

1 is a schematic view of a capacitance sensor for measuring a measured variable according to an embodiment of the present invention;

FIG. 2 shows an electrode arrangement in a sensor for measuring a measured variable according to an exemplary embodiment of the present invention; FIG.

3a shows an equivalent circuit diagram for the electrode group circuit in the sensor shown in FIG. 1 when measuring a first differential capacitance; FIG. 3b shows an equivalent circuit diagram for the electrode interconnection in the sensor shown in FIG. 1 according to an exemplary embodiment of the present invention when measuring a second differential capacitance;

4 shows a circuit with which the electrode pairs can be controlled in order to determine the first and the second differential capacitance;

FIG. 5 shows curves for the dependence of the first differential capacitance and the second differential capacitance on a rotational angle of the sensor; FIG.

6 shows an exemplary embodiment of a processing device in a sensor for measuring a measured variable according to an exemplary embodiment of the present invention;

Fig. 7 is a conventional capacitance sensor for determining an inclination;

8 shows an equivalent circuit diagram for self-forming capacitors in the conventional one shown in FIG

Sensor;

9 shows an electronic evaluation circuit in order to generate an output signal on the conventional sensor shown in FIG. 8;

10 shows an electrode arrangement in a further conventional sensor; and

11 is an equivalent circuit diagram explaining how two differential capacitances are formed in the sensor shown in FIG. FIG. 1 shows a capacitance sensor 100 according to an embodiment of the present invention. The capacitance sensor 100 has a first electrode pair 103, a second electrode pair 105 and a liquid 106, which is arranged between the first electrode pair 103 and the second electrode pair 105.

Via a first switch 107, a first electrode 103a and a second electrode 103b of the first electrode pair 103 can be conductively connected to one another. Via a second switch 109, a third electrode 105a and a fourth electrode 105b of the second electrode pair 105 can be conductively connected to one another.

A first differential capacitance meter 111 is connected to the first electrode 103a, the third electrode 105a, and the fourth electrode 105b. A second differential capacitance meter 113 is connected to the first electrode 103a, the second electrode 103b, and the fourth electrode 105b.

A driver 115 opens and closes the first switch 107 and the second switch 109 and triggers a measurement in the first differential capacitance meter 111 and in the second differential capacitance meter 113. A processor 117 receives an output signal from the first differential capacitance meter 111 and an output signal from the second differential capacitance meter 113, and provides a signal depending on the two received output signals.

A. Measuring a first differential capacity

At a first measuring time, the driving device 115 closes the first switch 107, opens the second one Switch 109 and triggers a measurement in the first differential capacity meter 111. By closing the switch 107, the first electrode 103a and the second electrode 103b of the first pair of electrodes 103 are electrically connected. By opening the switch 109, the third electrode 105a and the fourth electrode 105b are electrically disconnected, so that a first sub-capacitor is formed between the third electrode 105a and the first electrode pair 103 and a second sub-capacitor is formed between the fourth electrode 105b and the first electrode pair 103 , A corresponding equivalent circuit diagram for the interconnection of the first to fourth electrodes will be explained in Fig. 3a.

The capacitance of the first sub-capacitor and of the second sub-capacitor depend on an alignment or arrangement of the dielectric liquid 106 between the first electrode pair 103 and the second electrode pair 105. The arrangement of the liquid 106 in turn depends on an orientation of the capacitance sensor with respect to a horizontal or a horizontal surface and thus with respect to the gravitational field. When the capacitance sensor 100 is rotated right about a rotation axis 119, the proportion of the area of the third electrode 105a covered by the liquid 106 increases. A clockwise rotation of the sensor 100 is represented by an arrow 121 in FIG. At the same time, the area of the fourth electrode 105b covered by the liquid 106 decreases in a right turn of the sensor 100.

Since the liquid has a different or higher dielectric constant than air, the capacitance of the first partial capacitor and the second partial capacitor depends on an arrangement of the dielectric liquid 106 with respect to the third electrode 105a and with respect to the fourth electrode 105b. The first differential capacitance meter 111 determines the capacitance of the first sub-capacitor and the capacitance of the second sub-capacitor. Subsequently, the first differential capacitance meter 111 subtracts the capacitance of the second partial capacitor from the capacitance of the first partial capacitor and determines therefrom a first differential capacitance. The first differential capacitance meter 111 then generates an output signal at its output, which is dependent on the first differential capacitance and is received by the processing device 117.

Since, in a reference position shown in FIG. 1, the capacitance of the first partial capacitor is minimal and the second partial capacitor is maximum, the value of the first differential capacitance in the reference position is minimal.

B. determining a second differential capacity

For this purpose, the drive device 115 opens the first switch 107 at a second measurement time, closes the second switch 109, and triggers a measurement in the second differential capacitance meter 113. By opening the first switch 107, the first electrode 103a and the second electrode 103b of the first pair of electrodes 103 are electrically separated from each other. At the same time, the third electrode 105a and the fourth electrode 105b of the second electrode pair 105 are electrically connected to each other. Thus, a third partial capacitor forms between the first electrode 103a and the second electrode pair 105 and a fourth partial capacitor between the second electrode 103b and the second electrode pair 105.

The capacitance of the third sub-capacitor and the fourth sub-capacitor also depend on the position of the dielectric liquid 106. However, the second electrode pair 105 is here rotated by 90 ° relative to the first electrode pair 103, so that the third subconcept capacitor and the fourth sub-capacitor have the same capacity, in the reference position shown in Fig. 1.

The second differential capacitance meter 113 subtracts a value of the capacitance of the fourth partial capacitor from a value of the capacitance of the third partial capacitor and determines therefrom a second differential capacitance. The second differential capacitance meter 113 then generates an output signal at its output, which is dependent on the second differential capacitance and is received by the processing device 117.

The processing device 117 uses the signal received from the first differential capacitance meter 111 and the signal received from the second differential capacitance meter 113 to determine a rotation of the sensor 100 about the rotation axis 119 in a range of -180 ° to + 180 ° or in a range of 0 ° to 360 ° and thus an inclination of the sensor 100 relative to the horizontal. The method steps which take place in the processing device 117 for this purpose are explained in more detail below.

It is advantageous on the capacitance sensor shown in Fig. 1 according to an embodiment of the present invention that in a space-saving manner, two pairs of electrodes 103, 105 are arranged opposite one another. The attachment of further electrodes around the semicircular electrodes is thus eliminated.

FIG. 2 illustrates in an exploded view a structure of a sensor 122 according to an embodiment of the present invention in a housing. The housing consists of a first housing element 123 with a cavity in the first housing element 123 and a second housing element 127 with a surface 129 of the second housing element 127. The first electrode pair 103 is arranged on a surface 125 of a cavity in the first housing element 123, while the second electric The pair 105 is disposed on the surface 129 of the second housing member 127.

The first electrode 103 a, the second electrode 103 b, the third electrode 105 a and the fourth electrode 105 b are here z. B. circular segment-shaped, while the cavity in the first housing member 123, for example, is cylindrical. The electrodes of the second pair of electrodes 105 are here z. B. circular segment and rotated by 90 ° to the electrodes 103 a, 103 b of the first pair of electrodes 103.

FIG. 3a illustrates an equivalent circuit diagram for the interconnection of the first to fourth electrodes 103a-b, 105a-b in the measurement of the first differential capacitance. As already explained above, in order to measure the first differential capacitance, the first electrode 103a and the second electrode 103b are electrically conductively connected to one another, while the third electrode 105a and the fourth electrode 105b are separated from one another. The first differential capacitance meter 111 is connected to a first terminal 131a with the third electrode 105a, connected to the fourth electrode 105b via a second terminal 131b and to the first electrode pair 103 via a third terminal 131c. Via the connections 131a, 131c, the first differential capacitance meter determines the capacitance of the first partial capacitor and, via the connections 131b, 131c, the capacitance of the second partial capacitor. Subsequently, as already explained above, it forms the first differential capacitance.

FIG. 3b illustrates an equivalent circuit diagram for the interconnection of the first to fourth electrodes in the measurement of the second differential capacitance. As already explained above, the third electrode 105a and the fourth electrode 105b are electrically conductively connected while the first electrode 103a and the second electrode 103b are electrically separated from one another. The second Differential capacitance meter 113 is connected to the second electrode pair 105 at a fourth terminal 131d and connected to the first electrode 103a via a fifth terminal 131e and to the second electrode 103b via a sixth terminal 131f. Via the fourth connection 131d and the fifth connection 131e, the second capacitance meter 113 determines the capacitance of the third partial capacitor and via the fourth connection 131d and the sixth connection 131f the capacitance of the fourth partial capacitor. It then forms the second differential capacitance from the capacitance of the third partial capacitor and the fourth partial capacitor.

Fig. 4 illustrates a modified embodiment of the embodiment of the present invention shown in Fig. 1. Compared with the embodiment of the present invention shown in FIG. 1, the modified embodiment shown in FIG. 4 has a microcontroller 133 with a first microcontroller connection or first connection of the microcontroller 135a, a second microcontroller connection or second connection of the microcontroller 135b and a third microcontroller terminal and third terminal of the microcontroller 135c and a first to fourth switch 137a-d on. The capacitance sensor 100 with the modified embodiment shown in FIG. 4 is used to measure a tilt angle.

In this case, the measurement of the current position of the sensor or capacitance sensor 100 takes place such that the electronics or the microcontroller 133 are the switches 137a-d for the realization of the electrode interconnections shown in Fig. 3a and Fig. 3b, respectively assigns a switch position of the switch.

A. Measurement of the first differential capacity For this purpose, the first to fourth switches 137a-d are actuated by the microcontroller 133 at the first measuring time such that they each have the switch position represented by the solid line in FIG. Thus, the first electrode 103a and the second electrode 103b are connected to each other via the first changeover switch 137a and the second changeover switch 137b, and connected to the second microcontroller port 135b. The third electrode 105a is connected to the first microcontroller port 135a via the third switch 137c. The fourth electrode 105b is electrically conductively connected to the third microcontroller terminal 135c via the fourth switch 137d.

The microcontroller 133 determines the capacitance of the first partial capacitor via the first microcontroller connection 135a and the second microcontroller connection 135b, and the capacitance of the second partial capacitor via the third microcontroller connection 135c and the second microcontroller connection 135b. In the microcontroller 133, the first differential capacitance is then determined, for example, by means of the evaluation circuit 51 shown in FIG.

B. Measurement of the second difference capacity:

After determining the first differential capacitance, the switches 137a-d are placed in the dashed state shown in FIG. 4 at the second measuring time. Thus, the third electrode 105a and the fourth electrode 105b are short-circuited via the third switch 137c and the fourth switch 137d and connected to the second microcontroller terminal 135b. At the same time, the first electrode 103a is connected to the first microcontroller port 135a via the first switch 137a. The second electrode 103b is coupled to the third microcontroller port 135c via the second switch 137b. About the first Microcontroller port 135a and the second microcontroller port 135b determines the microcontroller 133, the capacity of the third sub-capacitor and the third microcontroller port 135c and the second microcontroller port 135b, the capacitance of the fourth sub-capacitor. In the microcontroller 133, the second differential capacitance is then again determined, for example, with the evaluation circuit shown in FIG. 9.

The sequences or the clock for the switching of the first 137a to fourth 137d switch or the definition of the distances between the first and the second measurement time, is z. B. in a control software that is processed by the microcontroller 133, deposited.

By means of a comparison table, the z. B. is also implemented in software on the microcontroller 133, the microcontroller 133 determines an inclination of the sensor. In the comparison table, for each value of the first differential capacitance, there are two corresponding values of the inclination angle in a range from 0 ° to 360 °. Also, for the value of the second differential capacitance, there are two corresponding values of the inclination angle in a range of 0 ° to 360 ° in the comparison table. The microcontroller 133 now compares the two corresponding values of the angle of inclination for the first differential capacity with the two corresponding values of the angle of inclination for the second differential capacity and determines the value of the angle of inclination in the two pairs of values, ie in the corresponding value pair for the first differential capacity and the corresponding value pair for the second differential capacity. This value corresponds to the actual tilt angle by which the capacitance sensor is deflected. Thus, a determination of the inclination angle in a range of 0 ° to 360 ° is possible. In Fig. 5, the dependence of the tilt angle of the first differential capacitance, which is provided in Fig. 5 by the reference numeral .DELTA.C1, and the second differential capacitance, which is provided in Fig. 5 by the reference numeral .DELTA.C2 is explained. On the x-axis of the graph shown in Fig. 5, the values of the inclination angle in a clockwise rotation of the sensor 100 in Fig. 1 are plotted around the rotation thing 119 in a range of 0 ° to 360 °. In the reference position of the sensor 100 shown in FIG. 1, the inclination angle is 0 °. On the y-axis, a normalized to the range of the differential capacitance value of the first ΔC1 and the second ΔC2 differential capacity, to which a factor of 0.5 has been added, plotted. In other words, a ratio of the measured differential capacitance to a difference between a maximum value and a minimum value of the differential capacitance is plotted on the y axis. A dashed line explains a course of the normalized values of the first differential capacitance ΔC1 as a function of the angle of inclination. A solid line explains a course of the normalized values of the second differential capacitance ΔC2 as a function of the angle of inclination.

In the following it will be explained how an inclination angle of 120 ° can be determined with the arrangement shown in FIG. 4 according to a modified embodiment of an embodiment of the present invention. It is assumed that the angle of inclination during the

Measurement of the first differential capacity ΔC1 and the second ΔC2 differential capacity does not change.

First, the microcontroller 133 sets the switches 137a-d to the switch position indicated by the solid line to determine the first differential capacitance. As is apparent from Fig. 5, results in a tilt angle of 120 ° of the sensor, a normalized value for the first differential capacitance .DELTA.C1 of 0.625. The microcontroller 133 thereby determines a first inclination angle value 139a of 120 °, which corresponds to the normalized first differential capacitance ΔC1 of 0.625, and a second inclination angle value 139b of 240 °, which also corresponds to the normalized first differential capacitance ΔC1 of 0.625. The microcontroller 133 stores the first inclination angle value or intermediate measurement value 139 a and the second inclination angle value 139 b in a register, not shown, in the microcontroller 133.

Subsequently, the microcontroller 133 changes the position of the first to fourth switch 137a-d, so that they occupy the dashed line in Fig. 4 drawn position. As a result, the microcontroller determines the second differential capacitance ΔC2 by means of the signals applied to the first to third microcontroller ports 135a-c. At an angle of 120 °, the second differential capacitance ΔC2 assumes a normalized value of 0.875. This normalized value of 0.875 corresponds to two inclination angle values in the comparison table in the microcontroller, a third inclination angle value 141a of 60 ° and a fourth inclination angle value 141b of 120 °. The microcontroller 133 also stores the two tilt angle values 141 a, 141 b in the register (not shown) in the microcontroller 133.

Subsequently, the microcontroller reads out the four inclination angle values 139a, 139b, 141a, 141b from the register and compares them with each other. The first inclination angle value 139a and the fourth inclination angle value 141b thereby appear twice among the read-out inclination angle values. The microcontroller 133 detects this and notes that the value of the inclination angle or the measured variable is 120 °. This value of 120 ° he outputs by means of an output signal not shown here.

The offset of the two measured curves to one another corresponds to the rotation of the electrode pairs 103 and 105 relative to one another. On the basis of the signals for each of the two arrangements leaves Thus, the position of the crossed differential capacitor arrangement or the capacitance sensor 100 by a further logical computing stage, the z here. B. is implemented in a microcontroller, determine.

Thus, in the modified embodiment of the sensor 100 or the differential capacitor arrangement, a contacting of the electrodes 103a, 103b, 105a, 105b by means of the microcontroller 133 or an electrical circuit is possible such that two different ones depending on the contacting of the electrodes Differential capacitor arrangements can be contacted and read out, due to which the position of the dielectric liquid 106 and a fluid can be determined. However, instead of the dielectric liquid 106, an electrically conductive body whose position changes in accordance with the inclination of the sensor 100 could be arranged in the gap between the electrode pairs 103, 105.

In Fig. 6 it is shown how the processing means 117 in the sensor 100 shown in Fig. 1 according to an embodiment of the present invention can determine the value of the inclination angle as an alternative to the method explained above.

FIG. 6 shows an embodiment of the processing device 117 shown in FIG. 1. The first differential capacitance meter 111 is coupled to a first analog-digital converter 143, while the second differential capacitance meter 113 is coupled to a second analog-to-digital converter 145 , An output of the first analog-to-digital converter 143 is connected to a first value register 147, while an output of the second analog-to-digital converter 145 is connected to a second value register 149.

The first value register 147 is connected to a first assignment device 151, while the second value register 149 is coupled to a second assignment device 153. The first allocator 151 is connected to a first intermediate measurement value register 155a, and a second intermediate measurement value register 155b is connected. The second allocation means 153 is connected to a third measurement intermediate value register 157a and a fourth measurement intermediate value register 157b.

The first measurement intermediate value register 155a is coupled to a first comparison circuit 159a and a second comparison circuit 159b. The second measurement intermediate value register 155b is coupled to a third comparison circuit 159c and a fourth comparison circuit 159d.

The third measurement intermediate value register 157a is coupled to the first comparison circuit 159a and the fourth comparison circuit 159d. The fourth measurement intermediate value register 157b is coupled to the second comparison circuit 159b and the third comparison circuit 159c.

A read-out means 161 is electrically connected to each of the first to fourth comparison circuits 159a-d and connected to the first measurement intermediate value register 155a and the second measurement intermediate value register 155b. An output of the readout device 161 is connected to an input of the measured value register 163, and an output of the measured value register 163 is connected to an output connection 165 of the processing device 117.

The first analog-to-digital converter 143 converts a signal from the first differential capacitance meter 111 whose height depends on the first differential capacitance ΔC1 into a first value, preferably a first binary value, and stores this first value in the first value register 147. The second analog-to-digital converter 145 converts a signal from the second differential capacitance meter 113, the magnitude of which depends on the second differential capacitance ΔC2, into a second value, preferably a second binary value, at and stores this second value in the second value register 149. The first allocation device 151 reads out the first value from the first value register 147 and determines a first measurement intermediate value and a second measurement intermediate value by means of a comparison table and stores the first measurement intermediate value in the first measurement intermediate value register 155a and the second measurement intermediate value in the second measurement intermediate value register 155b. The first intermediate measurement value and the second intermediate measurement value correspond with the two possible inclination angle values by which the sensor 100 could be inclined at the measured value of the first differential capacitance ΔC1. The second assignment means 153 reads out the second value from the second value register 149 and determines a third measurement intermediate value and a fourth measurement intermediate value by means of a comparison table and stores the third measurement intermediate value in the third measurement intermediate value register 157a and the fourth measurement intermediate value in the fourth measurement intermediate value register 157b. The third measurement intermediate value and the fourth measurement intermediate value correspond to the possible inclination angle values by which the sensor 100 could be inclined at the measured value of the second differential capacitance ΔC2. In this case, the course of the inclination angle as a function of the first differential capacity ΔC1 and the second differential capacity ΔC2 still applies to the course shown in FIG.

The first comparison circuit 159a compares the first measurement intermediate value with the third measurement intermediate value. The second comparison circuit 159b compares the first measurement intermediate value with the fourth measurement intermediate value. The third comparison circuit 159c performs a comparison of the second measurement intermediate value with the fourth measurement intermediate value. The fourth comparison circuit 159d performs a comparison of the second measurement intermediate value with the third measurement intermediate value. In all comparison circuits 159a-d, the comparison of the measured intermediate values is carried out by means of an XOR function that returns a binary value of 0 if the two compared values are identical.

The read-out means 161 reads out the values of the first to fourth comparison circuits 159a-d and determines the values

Comparison circuit of the four comparison circuits, which supplies the binary value 0.

Then, when the first or the second comparison circuit 159a-b supplies the binary value 0, it reads the measurement intermediate value from the first measurement intermediate value register 155a, or if the third or fourth comparison circuit 159c-d supplies the binary value 0, the measurement intermediate value from the second one Measurement intermediate value register 155b. The reading intermediate reading is then written by the read-out 161 in the measured value register 163.

The four comparison circuits 159a-d thus determine a measured intermediate value from the first and second measured intermediate value, which is equal to a measured intermediate value from the third and fourth measured intermediate value. The intermediate measurement value occurring in both pairs of measurement intermediate values indicates the actual height of the inclination angle in a range of 0 ° to 360 °, by which the sensor 100 is inclined.

In the above embodiment of the present invention, a dielectric liquid is disposed between the first and second electrode pairs, but alternatively, any movable element may be disposed between the two electrode pairs affecting the first and second differential capacitance. A possible alternative would be an embodiment of the movable element as a rotatable electrode made of an electrically conductive material, which is preferably rotatably mounted with a small distance between, for example, frontally opposite electrodes. In the above embodiment of the present invention, the dielectric liquid, which is arranged between the first and the second electrode pair, a different dielectric constant than the surrounding medium, wherein any ratios of the dielectric constant of the liquid to the liquid surrounding medium are possible.

As an alternative to the dielectric liquid, it would also be possible to arrange an electrically conductive liquid between the electrode pairs whose arrangement between the electrodes is likewise z. B. is dependent on the inclination of the sensor. Also, the medium surrounding the liquid can be any substance which preferably changes its arrangement between the electrode pairs as a function of the measured variable. In the above embodiment of the present invention, the liquid between the first electrode pair 103 and the second electrode pair 105 is arranged so that it preferably completely overlaps with a reference position of the sensor with one of the electrodes of the first or the second pair of electrodes, but are any liquid levels alternatives.

In the above embodiment, the driver 115 is designed to alternately measure the first differential capacitance and the second differential capacitance, however, any of the operations of measuring the first differential capacitance and the second differential capacitance therefor are alternatives thereto. In addition, in the above embodiment of the present invention, the driving device is designed so that the first differential capacity and the second differential capacity are preferably measured within a period of less than ten seconds, but any time periods therefor are alternatives.

Alternatively, the drive device could also be designed so that, depending on a value of the inclination angle optionally a value of the inclination angle in Dependent on the first differential capacity or the second differential capacity is determined. For example, the drive device could be designed so that in a range of the inclination angle of -60 ° to 60 °, in which the first differential capacitance has a suitable sensitivity or linearity, the inclination angle is determined in dependence on a value of the first differential capacity, and a range of the inclination angle of 60 ° to 120 ° or of -120 ° to -60 °, in which the second differential capacitance has a suitable sensitivity or non-linearity, the inclination angle is determined as a function of the value of the second differential capacitance , In this case, any selection of the range end points at which the drive device switches from a measurement of the value of the first differential capacitance to a measurement of the value of the second differential capacitance or from a determination of the inclination angle as a function of the first differential capacitance to a determination of the inclination angle as a function of second differential capacity or vice versa switched, possible.

In the above embodiment of the present invention, the first and second electrode pairs are circular. However, any shapes of the first and second pairs of electrodes are alternatives thereto. In the above embodiment of the present invention, the first electrode and the second electrode and the third electrode and the fourth electrode are circular sector-shaped, but any shapes of the first to fourth electrodes are alternatives thereto.

In the above embodiment of the present invention, a rotation axis about which the sensor rotates preferably passes through the center of the first pair of electrodes and the center of the second pair of electrodes. However, any gradients of the axis of rotation about which the sensor rotates are alternatives to the first pair of electrodes and the second pair of electrodes. In the above embodiment of the In the above embodiment of the present invention, the axis of rotation is preferably perpendicular to the first pair of electrodes and perpendicular to the second pair of electrodes, however, any angles for arranging the axis of rotation to the first pair of electrodes and to the second pair of electrodes are alternatives. In the above embodiment of the present invention, the first electrode pair is arranged parallel to the second electrode pair, however, any arrangement of the electrode pairs with each other is possible.

In the above embodiment of the present invention, the first to fourth electrodes each have a semicircular shape, but any circle segment angles or other shapes of the electrodes are alternatives thereto. In the above embodiment of the present invention, in a plan view of the pairs of electrodes from a perpendicular viewing angle, the first pair of electrodes and the second pair of electrodes completely overlap in area, however, any overlaps of the pairs of electrodes are alternatives, as long as both electrodes of one pair of electrodes overlap with the other pair of electrodes.

In the above embodiment of the present invention, the two pairs of electrodes are circular and form mutually rotated pairs of surfaces, wherein a rotation angle by which the two pairs of surfaces are rotated to each other here z. B. is 90 °. However, any values of the angle by which the pairs of electrodes rotate with each other are alternatives.

In the above embodiment of the present invention, in FIG. 5, the waveforms of a function indicating a dependency of the first differential capacitance and the second differential capacitance on the inclination angle of the sensor and a first differential capacitance measurement magnification and a second differential capacitance Meßgrössenzusammenhangs shown, wherein the curves are identical, but are phase-shifted by a Flächenpaarrotations- angle to each other. However, any curves of the function of the first differential capacity and the second differential capacity as a function of the angle of inclination, which may not be identical, are alternatives thereto.

In the above embodiment of the present invention, the readout means 161 determines, by means of the first to fourth comparison circuits, the measurement intermediate value corresponding to the measurement value. In the comparison circuits, four measured intermediate values were compared with each other via an XOR function. The comparison circuits for this purpose combine a first and a second function input value or intermediate measurement value with a third and a fourth function input value. Then they determine the function output value from the four function output values at which one of the four comparison circuits supplies the binary value 0 as a function output value. However, any circuit implementations for this are alternatives which compare the first and second measurement intermediate values respectively with the third and fourth measurement intermediate values and also apply functions other than an XOR function.

In the above embodiment of the present invention, in Fig. 1, a first switch 107 and a second switch 109 are used to electrically connect or electrically separate the first and second electrodes and the third and fourth electrodes from each other. Here are any means for connecting or disconnecting the electrodes of the electrode pairs or implementations of the switches, such. As a field effect transistor switch or relay possible.

In the above embodiment of the present invention, there is shown in Fig. 4 an embodiment of the processing device which is a microcontroller. However, any computing devices that come from the are arbitrary computing devices that determine the measured value from the value of the first differential capacity and the value of the second differential capacity by means of a software in which a lookup table is implemented, alternatives. The performed by the microcontroller 133 control of the position of the switch can be performed by any controller, which is not on the microcontroller 133 but z. B. can be implemented in an external logic circuit.

In the above exemplary embodiment, the sensor is embodied, for example, as a differential capacitor arrangement in a housing, the housing having a cavity, at the first end side of which at least two electrodes are arranged and at the second end side of which at least two further electrodes are arranged. In this case, the electrodes are arranged on the first end side opposite to the electrodes on the second end side rotated by a rotation angle in a range of 0 ° to 180 °. The cavity is in this case formed in at least one housing element which has the housing. At the same time a dielectric liquid is arranged in the cavity, which partially fills the cavity. However, alternatives to this are sensors of arbitrary design, in which the electrodes of a first pair of electrodes and of a second pair of electrodes are arranged, for example with an arbitrary holder, that a space is formed between them, in which a movable element is arranged, wherein the electrodes of a pair of electrodes each overlap with the two electrodes of the other pair of electrodes. Also, then the dielectric liquid z. B. forms the movable element, are arranged in a separate container.

Claims

claims

1. Sensor (100) for measuring a measured variable, with the following

features:

a first electrode pair (103) having a first electrode (103a) and a second electrode (103b);

a second electrode pair (105) having a third electrode (105a) and a fourth electrode (105b);

wherein a gap is formed between the first electrode pair (103) and the second electrode pair (105), and wherein the electrodes of the first and second electrode pairs (103, 105) are arranged so that one electrode of a pair of electrodes is connected to both of the electrodes overlaps other pairs of electrodes;

a movable member (106) whose position with respect to the first and second pairs of electrodes (103, 105) depends on the measured quantity and which is arranged between the first pair of electrodes (103) and the second pair of electrodes (105);

a capacitance measuring device (111, 113) for measuring a first differential capacitance (ΔC1) between a first sub-capacitor, which is conductively connected to one another by the first electrode pair (103), in which the first (103a) and the second electrode (103b) are connected to one another third electrode (105a) and a second sub-capacitor formed by the first electrode pair (103) and the fourth capacitor electrode (105b) and measuring a second differential capacitance (ΔC2) between a third sub-capacitor by the second electrode pair (105) in which the third (105a) and the fourth electrode (105b) are conductively connected to each other, and the first electrode (103a) is formed, and a fourth sub-capacitor formed by the second electrode pair (105) and the second electrode (103b); and

a processing device (117) for generating a measured value for the measured variable using the first differential capacitance (ΔC1) and the second differential capacitance (ΔC2).

The sensor (100) according to claim 1, wherein the movable element (106) has a dielectric arranged to influence the first differential capacitance (ΔC1) and the second differential capacitance (ΔC2) depending on the measurand.

A sensor (100) according to any one of claims 1 or 2, which is an inclination sensor and is adapted to determine an inclination of the sensor (100) with respect to a reference direction, wherein the movable member (106) comprises a liquid, the arrangement thereof the first electrode pair (103) and the second electrode pair (105) depends on the inclination of the sensor (100) and has a different dielectric constant than a medium surrounding the liquid in the gap.

4. Sensor (100) according to claim 3, wherein the liquid has a level such that it at a reference position of the sensor (100) with one of the E- electrodes of the first or the second pair of electrodes (103, 105) completely overlaps.

A sensor (100) according to any one of claims 1 to 4, wherein said capacitance measuring means (111, 113) is adapted to alternately measure said first differential capacitance (ΔC1) and said second differential capacitance (ΔC2).

6. Sensor (100) according to one of claims 1 to 5, wherein the capacitance measuring device (111, 113) designed is to measure the first differential capacitance (ΔC1) and the second differential capacitance (ΔC2) within a period of less than ten seconds.

A sensor (100) according to any one of claims 1 to 6, which is a tilt sensor, and wherein the capacitance measuring means (111, 113) is adapted to operate in a first range depending on an inclination angle about which the inclination sensor is inclined of the inclination angle to determine the first differential capacity (.DELTA.C1) and to determine the second differential capacity (.DELTA.C2) in a second range of the inclination angle.

The sensor (100) according to any one of claims 1 to 7, wherein the first electrode pair (103) is circular, and the first electrode (103a) and the second electrode (103b) are circular sector shaped, and the sensor (100) is a tilt sensor which is adapted to rotate about an axis of rotation (119) and to determine a rotation angle dependent on an inclination of the sensor (100), the axis of rotation (119) passing through the center of the first pair of electrodes (103), and the first pair of electrodes is arranged in a plane perpendicular to the axis of rotation (119), and the second pair of electrodes is arranged in a plane parallel to the plane of the first pair of electrodes such that it completely covers the first pair of electrodes at each angle of inclination, so that the second Difference capacity (ΔC2) depends linearly on the rotation angle.

The sensor (100) according to claim 8, wherein the first electrode (103a) and the second electrode (103b) have a semicircular shape such that a range of the rotation angle within which the second differential capacitance (ΔC2) changes with a rotation angle changes, becomes maximum.

The sensor (100) according to any one of claims 1 to 9, wherein the second electrode pair (105) is circular, and the third (105a) and fourth (105b) electrodes are circular sector shaped, and the sensor is a tilt sensor designed is to rotate about an axis of rotation (119) and to determine a rotation angle dependent on an inclination of the sensor (100), wherein the axis of rotation (119) passes through the center of the second pair of electrodes (105) and the second pair of electrodes in one plane is arranged perpendicular to the axis of rotation (119), and the first pair of electrodes (103) is arranged in a plane parallel to the plane of the second pair of electrodes (105) so that the second pair of electrodes (105) have a complete area bei at each angle of inclination - Covered so that the first differential capacitance (ΔC1) depends linearly on the rotation angle.

The sensor (100) according to claim 10, wherein the third electrode (105a) and the fourth electrode (105b) have a semicircular shape such that a range of the rotation angle within which the first differential capacitance (ΔC1) changes as the angle of rotation changes , maximum becomes.

12. Sensor (100) according to one of claims 1 to 11, wherein the first pair of electrodes (103) and the second pair of electrodes (105) have the same shape and each completely overlap.

13. A sensor (100) according to one of claims 1 to 12, wherein the first (103) and the second electrode pair (105) and the first (103a), the second (103b), the third (105a) and the fourth (103 105b) are semicircular electrodes and form mutually rotated pairs of surfaces.

14. A sensor (100) according to claim 13, which is an inclination sensor and is adapted to determine an inclination angle with respect to a reference direction, wherein the first differential capacitance (ΔC1) and the second differential capacitance (ΔC2) have identical waveforms of a function having a Dependency of the first (.DELTA.C1) and the second differential capacitance (.DELTA.C2) indicating the inclination angle, wherein the waveforms are phase-shifted by a surface pair rotation angle to each other.

15. Sensor (100) according to claim 13, wherein the two pairs of surfaces (103, 105) are rotated relative to one another by a rotation angle, and wherein the processing device (117) is designed to take into account the measured value for the measured variable determining a first differential capacitance measurement quantity relationship for the first difference capacitance (ΔC1) and taking into account a second differential capacitance measurement magnitude relationship for the second differential capacitance (ΔC2), the first differential capacitance measurement context and the second differential capacitance measurement relationship being identical but out of phase with each other, and wherein Phase shift depends on the rotation angle.

16. The sensor (100) according to claim 15, wherein the processing device (117) is configured to compare a value of the first (ΔC1) and a value of the second differential capacitance (C2) with a look-up table and to determine therefrom the measured value.

17. A sensor according to claim 16, wherein the processing device is configured to transmit the value of the first differential capacitance and the value of the second differential capacitance to a computing device that is designed to by means of a Software in which the lookup table is implemented to determine the metric.

18. The sensor according to claim 1, wherein the processing device is configured to determine a first measured intermediate value and a second measured intermediate value from a value of the first differential capacitance, and a value of the second differential capacitance (ΔC2) to determine a third and a fourth measured intermediate value, wherein a measured intermediate value of the first and the second measured intermediate value is equal to a measured intermediate value from the third and from the fourth measured intermediate value, the first and the second measured intermediate value respectively with the third and the Compare the fourth measurement intermediate value to identify the two measurement intermediate values that are the same, and to determine the measured value as a function of the two same measurement intermediate values.

The sensor (100) of claim 18, wherein the processing means (117) is adapted to convert the first to fourth measurement intermediate values into first to fourth binary input values, and the first and second binary input values to each of them by an XOR function third and fourth binary function input values to determine a pair of the four pairs of associated function input values that provides a binary function output value of zero, and to determine the measurement value in response to one of the two associated function input values in the particular pair.

20. A sensor according to claim 1, further comprising a drive device configured to drive a circuit element such that while the capacitance measurement device receives the first differential rence capacitance (ΔC1), the circuit element conductively connects the first electrode (103a) and the second electrode (103b), and while the capacitance measuring device detects the second differential capacitance (ΔC2), the circuit element detects the third electrode (105a) and the fourth one Conductively connects electrode (105b).

21. Sensor (100) according to claim 20, wherein the circuit element has a first switch (107) which is arranged between the first (103a) and the second electrode (103b) and has a second switch (109), which is arranged between the third (105a) and the fourth electrode (105b), wherein the driving means (115) is adapted to close the first switch and to open the second switch while the capacitance measuring device detects the first differential capacitance (ΔC1), and opening the first switch (107) and closing the second switch (109) while the capacitance measuring device detects the second differential capacitance (ΔC2).

22. Sensor (100) according to claim 20, which has a microcontroller (133), which comprises the drive device (115), wherein the microcontroller (133) is designed, while the capacitance measuring device (111, 113) the first differential capacitance (.DELTA.C1 ) determines to switch a first changeover switch (137a) connected to the first electrode (103a) and a second changeover switch (137b) connected to the second electrode (103b) so that the first one (137a) 103a) and the second (103b) electrode are connected to a first terminal (135b) of the microcontroller (133), and a third switch (137c) connected to the third electrode (105a) so as to switch a second one Terminal (135a) of the microcontroller (133) is connected to the third electrode (105a), and a fourth switch (137d), connected to the fourth electrode (105b), so that a third terminal (135c) of the microcontroller (133) is connected to the fourth electrode (105b), and while the capacitance measuring device (111, 113) is the second Difference capacitance (ΔC2) determines to switch the first switch (137a) so that the first electrode (103a) is connected to the second terminal (135a) of the microcontroller (133) and to switch the second switch (137b) so that the second electrode (103b) is connected to the third terminal (135c) of the microcontroller (133), and the third (137c) and the fourth (137d) switch are switched so that the first terminal (135b) of the microcontroller (133) is connected to the third (105a) and the fourth electrode (105b).