Electrodynamic acoustic transducer with conductive membrane for coil connection

Abstract

An electrodynamic acoustic transducer (1a . . . 1c) is presented, which comprises a housing (2), a membrane (3), a coil arrangement (6a . . . 6f) attached to the membrane (3) and a magnet system (9, 10, 11). The coil arrangement (6a . . . 6f) comprises a plurality of coils (7, 8) each having two terminals (T7, T8, T7a, T8a, T7b, T8b, T78) being static in relation to the housing (2). At least one pair of coils (7, 8) has one terminal (T78) in common, whereas the remaining terminals (T7, T8, T7a, T8a, T7b, T8b) are individual terminals (T7, T8, T7a, T8a, T7b, T8b). Connecting wires (12, 13, 12a, 13a, 12b, 13b) connect the coils (7, 8) with the individual terminals (T7, T8, T7a, T8a, T7b, T8b), and a conductive layer or path (14a . . . 14g) attached to the membrane (3) electrically connects the coils (7, 8) with the common terminal (T78).

Claims

1. An electrodynamic acoustic transducer, comprising: a housing; a membrane; a coil arrangement attached to the membrane, wherein the coil arrangement comprises a plurality of coils each having two terminals being static in relation to the housing, wherein at least one pair of coils has one terminal in common and wherein the remaining terminals are individual terminals; a magnet system being designed to generate a magnetic field transverse to a longitudinal direction of a wound wire of the coil arrangement and out of the membrane; connecting wires connecting the coils at individual connecting points, which are between the connecting wires and the coils, with the individual terminals; and a conductive layer or path attached to the membrane out of the magnetic field, which conductive layer or path electrically connects the coils and the common terminal; and wherein a wire connects a common connecting point between the coils with the conductive layer or path.

2. The electrodynamic acoustic transducer as claimed in claim 1, wherein the conductive layer or path comprises or consists of a conductive adhesive, glue and/or paint attached to the membrane.

3. The electrodynamic acoustic transducer as claimed in claim 1, wherein the conductive layer or path comprises or consists of a metallic foil attached to the membrane.

4. The electrodynamic acoustic transducer as claimed in claim 1, wherein the resistance of the conductive layer or path is higher than the real value of the impedance of each of the coils, which the conductive layer or path is connected to.

5. The electrodynamic acoustic transducer as claimed in claim 3, wherein a wire connects a common connecting point between the coils with the conductive layer or path.

6. The electrodynamic acoustic transducer as claimed in claim 1, wherein at least two coils of the coil arrangement are wound in opposite directions.

7. The electrodynamic acoustic transducer as claimed in claim 1, wherein the coil arrangement comprises coils, which are identical in shape and which are mounted to each other head first.

8. The electrodynamic acoustic transducer as claimed in claim 1, wherein individual connecting points between the connecting wires and the coils and/or common connecting points are symmetrically arranged on the coil arrangement.

9. The electrodynamic acoustic transducer as claimed in claim 8, wherein individual connecting points between the connecting wires and the coils and/or common connecting points are symmetrically arranged on the coil arrangement: a) seen in a direction perpendicular to a plane encompassed by a wound wire respectively by a wire loop and/or b) with respect to a height extension perpendicular to a plane encompassed by a wound wire respectively by a wire loop.

10. The electrodynamic acoustic transducer as claimed in claim 8, wherein the individual terminals and/or common terminals are symmetrically arranged around the coil arrangement.

11. The electrodynamic acoustic transducer as claimed in claim 9, wherein the individual terminals and/or common terminals are symmetrically arranged around the coil arrangement.

12. The electrodynamic acoustic transducer as claimed in claim 8, wherein the connecting wires are symmetrically arranged around the coil arrangement.

13. The electrodynamic acoustic transducer as claimed in claim 12, wherein the connecting wires are substantially identical in shape.

14. The electrodynamic acoustic transducer as claimed in claim 8, wherein connecting points and/or common connecting points are arranged in a bonding plane of two coils.

15. The electrodynamic acoustic transducer as claimed in claim 1, wherein the coil arrangement comprises two coils.

16. The electrodynamic acoustic transducer as claimed in claim 1, wherein the coils are polygonal in shape.

17. The electrodynamic acoustic transducer as claimed in claim 16, wherein a connection between the conductive layer or path and the coils is arranged in a corner of the coil arrangement.

18. The electrodynamic acoustic transducer as claimed in claim 16, wherein multiple connecting wires connect the coil arrangement at its corners.

19. The electrodynamic acoustic transducer as claimed in claim 17 wherein multiple connecting wires connect the coil arrangement at its corners.

20. The electrodynamic acoustic transducer as claimed in claim 16, wherein multiple connecting wires connect the coil arrangement at the center of its longitudinal sides.

21. The electrodynamic acoustic transducer as claimed in claim 17, wherein multiple connecting wires connect the coil arrangement at the center of its longitudinal sides.

22. The electrodynamic acoustic transducer as claimed in claim 1, wherein in that the coils are round, in particular circular, in shape.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other aspects, features, details, utilities, and advantages of the invention will become more fully apparent from the following detailed description, appended claims, and accompanying drawings, wherein the drawings illustrate features in accordance with exemplary embodiments of the invention, and wherein:

(2) FIG. 1 shows a cross sectional view of an exemplary transducer with a conductive path on the membrane;

(3) FIG. 2 shows the transducer of FIG. 1 in top view;

(4) FIG. 3 shows a transducer similar to the transducer of FIGS. 1 and 2, but with a conductive path on the lower side of the membrane;

(5) FIG. 4 shows a simplified circuit diagram of the transducer shown in FIGS. 1 and 2;

(6) FIG. 5 shows a further example of a transducer in top view with improved symmetry;

(7) FIG. 6 shows a detailed cross sectional view of an exemplary membrane with conductive paths or layers;

(8) FIG. 7 shows an example of a coil arrangement with the individual connecting points on the short sides of the coils in exploded view;

(9) FIG. 8 shows a top view of the coil arrangement of FIG. 7 in operating position;

(10) FIG. 9 shows a further example of a coil arrangement with the individual connecting points on the long sides of the rectangular coil arrangement;

(11) FIG. 10 shows individual connection points in the corners of a rectangular coil arrangement;

(12) FIG. 11 shows individual connection points at the center of the longitudinal sides of a rectangular coil arrangement and

(13) FIG. 12 shows an example of a circular coil arrangement.

(14) Like reference numbers refer to like or equivalent parts in the several views.

DETAILED DESCRIPTION OF EMBODIMENTS

(15) Various embodiments are described herein to various apparatuses. Numerous specific details are set forth to provide a thorough understanding of the overall structure, function, manufacture, and use of the embodiments as described in the specification and illustrated in the accompanying drawings. It will be understood by those skilled in the art, however, that the embodiments may be practiced without such specific details. In other instances, well-known operations, components, and elements have not been described in detail so as not to obscure the embodiments described in the specification. Those of ordinary skill in the art will understand that the embodiments described and illustrated herein are non-limiting examples, and thus it can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments, the scope of which is defined solely by the appended claims.

(16) Reference throughout the specification to various embodiments, some embodiments, one embodiment, or an embodiment, or the like, means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases in various embodiments, in some embodiments, in one embodiment, or in an embodiment, or the like, in places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Thus, the particular features, structures, or characteristics illustrated or described in connection with one embodiment may be combined, in whole or in part, with the features, structures, or characteristics of one or more other embodiments without limitation given that such combination is not illogical or non-functional.

(17) It must be noted that, as used in this specification and the appended claims, the singular forms a, an and the include plural referents unless the content clearly dictates otherwise.

(18) The terms first, second, and the like in the description and in the claims, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms include, have, and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

(19) All directional references (e.g., plus, minus, upper, lower, upward, downward, left, right, leftward, rightward, front, rear, top, bottom, over, under, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader's understanding of the present disclosure, and do not create limitations, particularly as to the position, orientation, or use of the any aspect of the disclosure. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein.

(20) As used herein, the phrased configured to, configured for, and similar phrases indicate that the subject device, apparatus, or system is designed and/or constructed (e.g., through appropriate hardware, software, and/or components) to fulfill one or more specific object purposes, not that the subject device, apparatus, or system is merely capable of performing the object purpose.

(21) Joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the spirit of the invention as defined in the appended claims.

(22) All numbers expressing measurements and so forth used in the specification and claims are to be understood as being modified in all instances by the term about, which particularly means a deviation of 10% from a reference value.

(23) FIG. 1 shows an example of an electrodynamic acoustic transducer 1a, which may be embodied as a loudspeaker, in cross sectional view. FIG. 2 depicts a top view of the transducer 1a. The transducer 1a comprises a housing 2 and a membrane 3 with a bending section 4 and a stiffened center section 5. Furthermore, the transducer 1a comprises a coil arrangement 6a attached to the membrane 3. The coil arrangement 6a comprises a first coil 7 and a second coil 8. The first coil 7 is arranged on top of the second coil 8 and concentric to the second coil 8 in this example. Generally, mounting the coils 7, 8 to each other may be done by means of an adhesive or glue.

(24) Furthermore, the transducer 1a comprises a magnet system with a magnet 9, a pot plate 10 and a top plate 11. The magnet system generates a magnetic field B transverse to a longitudinal direction of a wound wire of the coil arrangement 6a.

(25) The first coil 7 and the second coil 8 are electrically switched in series. Accordingly, the first coil 7 has an individual terminal T7 being static in relation to the housing 2. Similarly, the second coil 8 has an individual terminal T8 being static in relation to the housing 2. A connecting wire 12 connects the terminal T7 and the first coil 7 at an individual connecting point C7, and a connecting wire 13 connects the terminal T8 and the second coil 8 at an individual connecting point C8.

(26) Furthermore, the first coil 7 and the second coil 8 have a common terminal T78. A conductive path 14a, which is attached to the membrane 3 and which is electrically connected to the common connecting point C78 of the coils 7, 8, is used for this reason.

(27) Concretely, a short piece of wire 15 connects the common connecting point C78 of the coils 7, 8 and the conductive path 14a. On the outer, fixed part of the membrane 3 respectively conductive path 14a, the common terminal T78 is arranged. The conductive path 14a may comprise or consist of a conductive adhesive, glue and/or paint attached to the membrane 3 and/or a metallic foil attached to the membrane 3.

(28) The common connecting point C78 is arranged directly at the moving coils 7, 8. Beneficially, the connection at the moving coils 7, 8 is made with low ohmic resistance.

(29) FIG. 3 shows an alternative embodiment an electrodynamic acoustic transducer 1b, which is similar to the transducer 1a shown in FIGS. 1 and 2. In contrast, the conductive path 14b is not attached to the upper side of the membrane 3, but to the lower side. Additionally, the short piece of wire 15 is arranged on the outer side of the coil arrangement 6b, and not on the inner side. Finally, the common terminal T78 is vertically arranged on the circumference of the housing 2.

(30) FIG. 4 shows a simplified circuit diagram of the coil arrangement 6a shown in FIGS. 1 and 2. Concretely, FIG. 4 shows a voltage source, generating the voltage U.sub.In, which is fed to a serial connection of the first coil 7 and the second coil 8. In common designs, the voltage U.sub.In forms a sound signal, and a current I.sub.In caused by the voltage U.sub.In, which flows into the terminal T7 and out of the terminal T8 is comparably high. In contrast, currents flowing out of or into the common terminal T78, which are used for controlling tasks for example, are comparably low. One should note that the technical teaching disclosed in the context of FIG. 4 equally applies to the transducer 1b shown in FIG. 3.

(31) By means of the conductive path 14a, 14b the number of connecting wires and thus their influence on a movement of the membrane 3 can be reduced. The conductive path 14a, 14b has nearly no influence on a rocking or tumbling tendency of the coil arrangement 6a. However, to further improve symmetry, a further conductive path 14c may be arranged vis-a-vis of the first conductive path 14a or 14b as this is shown in FIG. 5. The further conductive path 14c may be electrically connected to the coils 7, 8 or not. Another possibility to improve symmetry is to attach a conductive layer to the whole membrane 3 or to attach a conductive layer with symmetric shape to the membrane 3. Further conductive paths 14d, 14e may be attached to the membrane 3 to connect further common connecting points between coils 7, 8, e.g. if the coil arrangement 6a comprises more than two coils 7, 8 switched in series and thus more than one common connecting point C78 and more than one common terminal T78.

(32) A further possibility to connect more than one common connecting point C78 in case of more than two coils 7, 8 switched in series is to arrange different conductive paths or layers on top of each other and/or on different sides of the membrane 3. In this context, FIG. 6 shows a cut out of an exemplary membrane 3 in cross sectional view (in particular of its bending section 4). Several conductive paths or layers are attached to the membrane 3, concretely a first conductive path or layer 14a on the upper side of the membrane 3, a second conductive path or layer 14f on top of the first conductive path or layer 14a and a third conductive path or layer 14g on the lower side of the membrane 3. The layers 14a, 14f, 14g may cover the whole area of the membrane 3 or parts thereof. Of course, the layers 14a, 14f, 14g may differ from each other in size and shape.

(33) FIG. 6 also shows that a layer or path 14a on top of the membrane 3 may be connected to a wire 15 by means of a feedthrough or via 16. On the lower side of the membrane 3 there is a contact pad 17, which the wire 15 is connected to. As there is also the third conductive path or layer 14g on the lower side of the membrane 3, the contact pad 17 is insulated by means of the insulation 18.

(34) It should be noted that FIGS. 1 to 6 just illustrate the possibilities how to arrange a conductive path or layer 14a . . . 14g on the membrane 3 and how to contact it with the coil arrangement 6a . . . 6b. Other embodiments are imaginable without departing from the spirit of the invention. For example, the wires of the coils 7, 8 may directly be led to the contact pad 17 or the conductive path or layer 14a . . . 14g so as to achieve the serial connection of the coils 7 and 8. In this case, the common connecting point C78 is situated on the connection pad 17 or the conductive path or layer 14a . . . 14g. Accordingly, the conductive path or layer 14a . . . 14g (including a via 16 as the case may be) forms the whole connection between the common connecting point C78 and the common terminal T78, whereas in the examples before, a short piece of wire 15 (which generally may be a short section of a coil wire of one of the coils 7, 8 or both coils 7, 8) is part of said connection. In any case, the common connecting point C78 is situated on the moving part of the electrodynamic transducer 1a . . . 1c. Beneficially, the connection between the coils 7 and 8 via the common connecting point C78 is low-ohmic, whereas the conductive path or layer 14a . . . 14g may have a higher resistance. Particularly, the resistance of the conductive path or layer 14a . . . 14g is higher than the real value of the impedance of each of the coils 7, 8, which the conductive path or layer 14a . . . 14g is connected to. Generally, the common connecting point C78 beneficially is arranged in a corner of a polygonal coil arrangement 6a . . . 6b (see also FIG. 10).

(35) In the examples hereinbefore, the conductive paths or layers 14a . . . 14g are attached to the outside of the membrane 3. However, this is not the only possibility. Instead, the conductive paths or layers 14a . . . 14g may also be arranged within the membrane 3. That means that the membrane 3 may have different layers, wherein some are conductive (e.g. metallic foils) and some are insulating like it is the case in a multilayer circuit board. Especially, if a high number of common connecting points C78 are to be connected, the membrane 3 may have the acoustic function on the one hand, and the function of a circuit board (including vias 16 as the case may be) on the other hand.

(36) FIGS. 7 and 8 show a top view of the coil arrangement 6a. FIG. 7 shows an exploded view with the coils 7, 8 displaced in diagonal direction, and FIG. 8 shows the coil arrangement 6a in operating position with the coils 7, 8 arranged above another.

(37) The individual connecting points C7, C8 are symmetrically arranged around the coil arrangement 6a, in particular with respect to the main axes x and y of the rectangular coil arrangement 6a.

(38) In a preferred embodiment, also the terminals T7, T8 are symmetrically arranged around the coil arrangement 6a as is shown in FIG. 8 (again with respect to the main axes x and y, respectively seen in a direction perpendicular to a plane encompassed by a wound wire respectively by a wire loopcase a). Furthermore, it is advantageous, if also the connecting wires 12, 13 are symmetrically arranged around the coil arrangement 6a (again with respect to the main axes x and y) as shown in FIG. 8. Finally, it is also advantageous, if the connecting wires 12, 13 are substantially identical in shape as this is the case in FIG. 8.

(39) Generally, the individual connecting points C7, C8 between the connecting wires 12, 13 and the coils 7, 8 may be symmetrically arranged on the coil arrangement 6a seen in the loop axis z respectively in a direction perpendicular to a plane encompassed by a wound wire respectively by a wire loop (case a). In this view, the wound wires of the coils 7, 8 appear as loops. This first approach of symmetry was discussed above.

(40) However, alternatively or in addition a second approach of symmetry of the individual connecting points C7, C8 may be applied to the transducer 1a. According to this approach, the individual connecting points C7, C8 between the connecting wires 12, 13 and the coils 7, 8 are symmetrically arranged on the coil arrangement 6a with respect to a height extension perpendicular to a plane encompassed by a wound wire respectively by a wire loop (case b). In particular, the individual connecting points C7, C8 may be arranged in the mid of a height extension of the coil arrangement 6a as this is the case in FIG. 1. The height extension of the coil arrangement 6a is oriented vertically in FIG. 1. However, the individual connecting points C7, C8 may also be arranged on top of the coil arrangement 6a or on its bottom.

(41) The individual connecting points C7, C8 beneficially may be arranged in a bonding plane of two coils 7, 8, which is the case in the example shown in FIGS. 1 to 3. In this way, manufacturing the coil arrangement 6a is comparably easy.

(42) In a very advantageous embodiment, the coil arrangement 6a comprises (two) coils 7, 8, which are identical in shape and which are mounted to each other head first. Using identical coils 7, 8 allows for manufacturing the coil arrangement 6a in a very economic way. Because the coils 7, 8 are mounted to each other head first, symmetry with regards to the height extension of the coil arrangement 6a is obtained in a very easy way.

(43) FIG. 9 now shows an embodiment of a coil arrangement 6c, which is quite similar to the coil arrangement 6a shown in FIG. 8. Instead, the individual connecting points C7, C8 are arranged on the y-axis.

(44) In the above examples, symmetry was disclosed with regards the individual connecting points C7, C8. Additionally or alternatively, the technical disclosure related to symmetry of individual connecting points C7, C8 can also applied to the common connecting points C78. Accordingly, symmetry can be obtained for individual connecting points C7, C8 and/or common connecting points C78.

(45) FIG. 10 shows a rectangular coil arrangement 6d with the individual connection points C7a, C7b, C8a and C8b in the corners of the coil arrangement 6d. The connection points C7a and C8a can belong to a first serial connection of the coils 7, 8, whereas the connection points C7b and C8b can belong to a second serial connection of coils. Accordingly, the individual connection points C7a, C7b, C8a and C8b can form the outer taps of two pairs of serially connected coils 7, 8.

(46) In view of polygonal coil designs, often a number of separate, rod-shaped magnets 9 (respectively magnets 9 shaped like a cuboid) instead of a single ring-shaped magnet 9 are used. Accordingly, the magnetic field is concentrated on the longitudinal sides of the polygon and is relatively weak in its corners. That is the reason why an individual connection point C7a, C7b, C8a, C8b and/or a common connection point C78 in the corner has nearly no influence on the performance of the transducer 1a . . . 1c.

(47) Generally, the effect of the magnetic stray field on the wires 12, 13, 12a, 13a, 12b, 13b is different than on the conductive paths 14a . . . 14e because of the different current levels and/or impedances. On the one hand, different current levels lead to different forces acting on the membrane 3 caused by the different currents flowing through the wires 12, 13, 12a, 13a, 12b, 13b respectively through the conductive paths 14a . . . 14e. On the other hand, different voltages are induced into the wires 12, 13, 12a, 13a, 12b, 13b respectively into the conductive paths 14a . . . 14e based on their different impedances. Since the strayfield is lower in the corner regions, as said it is beneficial to use these corner regions for any of the connection types between the coils 7,8 and the non-moving parts of the transducer 1a . . . 1c, i.e. for the wires 12, 13, 12a, 13a, 12b, 13b and/or the conductive paths 14a . . . 14e. Moreover, it is easier to connect the wires 12, 13, 12a, 13a, 12b, 13b respectively the conductive paths 14a . . . 14e in a region, where no magnets 9 are, for mechanical reasons.

(48) FIG. 11 shows a rectangular coil arrangement 6e, which is quite similar to the coil arrangement 6d shown in FIG. 10. In contrast, the individual connection points C7a, C7b, C8a and C8b are not arranged in the corners of the coil arrangement 6e, but at the center of its longitudinal sides.

(49) In view of the coil arrangement 6d and arrangement 6e, conductive paths 14a and 14c as shown in FIG. 5 may be used for the two common connection points. However, the common connection points C78 and the conductive paths 14a . . . 14e may also be arranged in the corners of the coil arrangement 6d, 6e.

(50) In FIGS. 1 to 11, the coil arrangements 6a . . . 6d respectively their coils 7, 8 are rectangular in shape. However, this is not the only possibility. A coil arrangement may also be quadratic in shape or round for example. FIG. 12 shows an example of a circular coil arrangement 6f. The terminals T7 and T8 are arranged opposite to each other in FIG. 12.

(51) It should be noted that although the examples depicted in the FIGS. 1 to 12 disclose circular and rectangular coil arrangements 6a . . . 6f, the invention relates to any shape of a coil arrangement 6a . . . 6f, in particular also to oval and polygonal shapes. Furthermore, the coils 7 and 8 may have the same height or different heights, the same diameter or different diameters as well as the same number of windings or different numbers of windings. Beneficially a coil arrangement 6a . . . 6f is symmetric with regards to the two main axes x and y.

(52) It should also be noted, that the coils 7, 8 may be wound in the same directions or in opposite directions.

(53) Furthermore, the invention does not just relate to two coils 7, 8, but to any number of coils 7, 8.

(54) Additionally, it should be noted that although symmetric design of individual connecting points C7, C8, C7a, C8a, C7b, C8b, common connecting points C78, terminals T7, T8, T7a, T8a, T7b, T8b, T78 and connecting wires 12, 13, 12a, 13a, 12b, 13b is advantageous, one may also deviate from a strict symmetric design. For example, the terminals T7, T8, T7a, T8a, T7b, T8b, T78 may be arranged in a different manner to provide a particular electrical interface. Furthermore, the shape of the connecting wires 12, 13, 12a, 13a, 12b, 13b may be different. Nevertheless, the influence of the connecting wires 12, 13, 12a, 13a, 12b, 13b on the movement of the membrane 3 may still be substantially symmetric by choosing an adequate design.

(55) It should be noted that the invention is not limited to the above mentioned embodiments and exemplary working examples. Further developments, modifications and combinations are also within the scope of the patent claims and are placed in the possession of the person skilled in the art from the above disclosure. Accordingly, the techniques and structures described and illustrated herein should be understood to be illustrative and exemplary, and not limiting upon the scope of the present invention. The scope of the present invention is defined by the appended claims, including known equivalents and unforeseeable equivalents at the time of filing of this application. Although numerous embodiments of this invention have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this disclosure.

LIST OF REFERENCES

(56) 1a . . . 1c electrodynamic acoustic transducer 2 housing 3 membrane 4 bending section 5 stiffened center section 6a . . . 6f coil arrangement 7 first coil 8 second coil 9 magnet 10 pot plate 11 top plate 12 . . . 13b connecting wire 14a . . . 14g conductive path 15 wire 16 feedthrough/via 17 contact pad 18 insulation B magnetic field C7 . . . C8b individual connecting point C78 common connecting point T7 . . . T8b individual terminal T78 common terminal x first main axis y second main axis z third main axis/loop axis U.sub.In input voltage I.sub.In input current