CN109143403B

CN109143403B - Method for calibrating an inductive positioning sensor and positioning sensor

Info

Publication number: CN109143403B
Application number: CN201810679159.9A
Authority: CN
Inventors: M.哈尔; K.伦茨
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2017-06-28
Filing date: 2018-06-27
Publication date: 2023-04-21
Anticipated expiration: 2038-06-27
Also published as: CN109143403A; DE102017210943A1

Abstract

A method for calibrating an inductive position sensor having at least one transmitter coil (116) and at least one receiver winding system (118) is proposed, which are designed on a circuit board (126 a) of the position sensor in the form of conductor tracks (128), wherein a balancing of a voltage U induced in the receiver coils (112, 114) of the receiver winding system (118) is achieved by switching off at least one calibration winding system (130) of the receiver winding system (118). According to the invention, the at least one calibration winding system (130) is disconnected in a method step (218) by means of mechanical milling of the conductor tracks (128) of the at least one calibration winding system (130).

Description

Method for calibrating an inductive positioning sensor and positioning sensor

Technical Field

The invention relates to a method for calibrating an inductive position sensor having at least one transmitting coil and at least one receiving winding system. Furthermore, the invention relates to a corresponding positioning sensor.

Background

Positioning sensors for positioning metallic objects concealed in building materials are currently commonly operated using inductive methods. The fact that the conductive and ferromagnetic material influences the properties of the electromagnetic coil arranged in the surroundings is used here. The change in the inductive properties caused by the metallic object is registered by the receiving circuit of such a positioning sensor. In this way, objects, such as metal enclosed in a wall, can be positioned by means of one or more coils guided on the wall.

The technical difficulty of detecting metallic objects is that the object to be positioned acts on the coil or coils of the positioning sensor with a small negative effect, in particular the positioning signal. This is especially true for the effects of non-ferromagnetic objects, such as technically important copper. This results in the induction effect of the coils with respect to each other being possibly significantly greater than the induction generated by the enclosed object in the receiving coil. The detectors of induction-based methods generally have a high signal that can be captured by the receiver coil of the detector, which signal is already measured by the receiver circuit of the positioning sensor without the influence of an external, metallic object. Such a high "background signal" (or also referred to as "bias") makes it difficult to detect very small induced changes caused by metal objects placed near the positioning sensor.

The following solutions are known from the prior art: the sensor signal, which is present in the form of a background signal in the absence of metallic objects, is reduced and the relative signal change is thereby amplified with respect to the background signal. For example, in DE 10 2004 047 188 Al, a sensor assembly for an inductive position sensor is known, which compensates for the background signal induced by the coil itself. The proposed device for locating metallic objects has at least one transmitter coil and at least one receiver winding system which are inductively coupled to one another, wherein the calibration of the device, in particular the compensation of the background signal induced by the coil itself, is achieved by means of a switching device which achieves a change in the effective number of turns of the receiver winding system.

Disclosure of Invention

A method for calibrating an inductive position sensor having at least one transmitter coil and at least one receiver winding system, which are embodied as conductor tracks on a circuit board of the position sensor, is proposed, wherein a balancing of a voltage U induced in the receiver coils of the receiver winding system is achieved by switching off at least one calibration winding system of the receiver winding system. According to the invention, at least one calibration winding system is disconnected in a method step by means of mechanical milling of the conductor tracks of the at least one calibration winding system.

The proposed method for calibrating an inductive position sensor is based on the disclosed concept that the geometry of the receiving winding system, for example the receiving coil, is modified in such a way that if no object to be positioned is positioned around the position sensor, the total magnetic flux generated by the receiving winding is lost or at least almost lost. This concept is known from DE 10 2004 047 188 A1.

In this case, the number of layers of one or more conductor loops and/or the conductor loops used, i.e. the geometry of the receiver winding system, is reduced by the receiver winding of the receiver winding system initially within the scope of the production. In order to carry out a change in the number of turns of the receiving winding and/or in the geometry of the receiving winding system, a method is proposed according to the invention in which the calibration winding system, i.e. in particular one or more receiving windings of the positioning sensor, are disconnected in a method step by means of mechanical milling of the at least one calibration winding system, which forms the conductor tracks of the respective winding. In the case of a suitable design of the conductor loop of the receiving winding, i.e. for example one or more receiving coils, the voltage is induced in the conductor loop part and/or the geometry of the receiving winding system is modified in such a way that, for example, an error voltage in the positioning sensor, which may occur due to non-compliant manufacturing tolerances, can just be compensated for.

It should be noted that the expression "milling of the conductor tracks" includes a similar machining of the conductor tracks, wherein the conductor tracks are interrupted by material removal, for example by means of drilling.

The method according to the invention achieves calibration of the position sensor, wherein balancing the voltage U induced in the receiving winding is achieved by switching off the calibration winding system of the receiving winding system. The calibration winding system may be composed of one or more compensation modules of a predetermined winding length and/or compensation windings. The compensation winding is to be understood here as meaning, in each case, the arc length of the current flow through the compensation winding, which is provided for the method according to the invention to be milled and, as a result of the milling, to effect a switching or change between at least two, preferably m, different alternative configurations. By means of this method, it is possible to change different combinations of the connections by milling the respective conductor tracks, so that the background signal of the positioning sensor, which is produced, for example, by incorrect assembly or by non-compliant manufacturing tolerances, is compensated for, so that an optimum balance is achieved.

Thus, a particularly simple, cost-effective and yet particularly effective method for accurately calibrating the positioning sensor according to the invention can be achieved according to the invention. Furthermore, a positioning sensor calibrated according to the method of the invention can be obtained, which produces as little background signal as possible, wherein incorrect placement of the coils, in particular of the transmit and receive coils, has as little influence as possible on the background signal.

In particular, a positioning sensor can be obtained in this way, which is calibrated after installation in the factory using the method according to the invention, so that an optimized operation can be achieved.

In one embodiment of the method according to the invention, the desired milling depth is obtained by mechanical milling of the test structure arranged on the circuit board in a method step preceding the method step of mechanical milling of the conductor tracks of the calibration winding system.

Since in the production of positioning sensors of the type mentioned, circuit boards equipped with electronic components are generally present, the use of working depth limiters for milling tools is generally not or only limitedly possible for the method steps of milling. In particular in the case of circuit boards which are provided with components and/or conductor tracks in a multi-layer manner, care must therefore be taken, in particular, to only process, i.e. separate, the desired layer provided with conductor tracks to be milled by means of milling. For this purpose, this requires milling at a milling depth which is as precisely defined as possible.

However, since the milling depth is taken in the milling tools known from the prior art starting from the support on which the circuit board to be milled is placed, tolerances in the thickness of the circuit board are also included within the possible accuracy of the milling depth. The prior art circuit boards typically have tolerances in terms of their thickness in the range of up to + -10%. In an exemplary 2.5. 2.5 mm thick circuit board, this corresponds to an absolute tolerance of ±250 μm. Therefore, the milling depth can also only be set to exactly ±250 μm.

The layers of the multiple layers of conductor tracks are usually separated on the circuit board by a substrate layer whose thickness is of the order of less than 500 μm. In the case of tolerances of the printed circuit board of, for example, ±250 μm, it is therefore not possible to ensure that the milling tool protrudes into the printed circuit board below the printed circuit board to be milled and damages its structure (in this case the thickness of the printed circuit board lies within the upper range of its tolerance, for example 2.75 mm) and/or that the printed circuit board to be milled is not completely cut off (in this case the thickness of the printed circuit board lies within the lower range of its tolerance, for example 2.25 mm), so that calibration of the positioning sensor is not performed.

By means of the method steps described above, according to the invention, the required milling depth is obtained by mechanical milling of the test structures provided on the circuit board and thus possible tolerances of the circuit board to be milled are taken into account in the determination of the milling depth. In particular, a method for calibrating an inductive position sensor that is independent of tolerances in the production, in particular on the basis of the production of circuit boards, can be obtained therefrom.

In the production of the conductor tracks of the positioning sensor, the test structure is likewise arranged on the circuit board, preferably in the immediate vicinity of the conductor tracks of the receiving winding system. In this context, "immediate vicinity" is to be understood to mean, in particular, a distance of the test structure from the receiving winding system of less than 10 cm, preferably less than 5 cm, particularly preferably less than 1 cm. Furthermore, a plurality of test structures according to the invention may also be provided on the circuit board. In one embodiment, a test structure is provided in the immediate vicinity of the calibration winding system, respectively.

In one embodiment of the method according to the invention, the test structure is implemented as a circuit, wherein the test structure is run by means of an evaluation circuit during the execution of the method steps for obtaining the required milling depth. In this way, a test structure that is particularly easy to handle can be manufactured and operated with particularly simple devices. Preferably, the test structure is designed as a circuit comprising at least one conductor track. Furthermore, the test structure may comprise, for example, a resistor for simple measurement of a particularly specific potential. As a result of the milling of the conductor tracks of the test structure, the closed circuit of the circuit is broken and the reduced voltage across the resistor (alternatively: the current applied to the resistor) is changed. By means of the evaluation circuit, the test structure can advantageously be observed during the execution of the method steps for obtaining the required milling depth, and the voltage change and/or the current change can be detected. In particular, in one embodiment of the method according to the invention, the desired milling depth is achieved when a voltage change and/or a current change is detected on the test structure by means of the evaluation circuit when the method steps for obtaining the desired milling depth are performed.

In one embodiment of the method according to the invention, the milling tool is positioned at the location of the test structure in a method step preceding the method step for obtaining the desired milling depth.

In one embodiment of the method according to the invention, a minimum milling depth is first set during the method steps for obtaining the desired milling depth, and then the milling depth is iteratively increased until the desired milling depth is reached. In this way, a particularly fine graduation can be achieved when determining the desired milling depth.

In one embodiment of the method according to the invention, in a method step of mechanical milling of the conductor tracks of the calibration winding system, a milling tool is first positioned at the location of the conductor tracks of the calibration winding system to be milled, and then the conductor tracks are milled to the desired milling depth.

With the method according to the invention it is thus ensured that the milled conductor tracks of the alignment winding system are completely milled, whereas the underlying (other), i.e. following the conductor tracks in the milling direction, conductor tracks are not milled. A particularly reliable calibration of the position sensor with a long-term stable conductor track can thus be achieved.

The invention also relates to a positioning sensor for positioning metallic objects, comprising at least one transmitter coil and at least one receiver winding system, which are coupled to one another in an inductive manner in particular and are designed on a circuit board of the positioning sensor in the form of conductor tracks, wherein at least one calibration winding system of the receiver winding system is provided for balancing a voltage U induced in the receiver coil of the receiver winding system, wherein the at least one calibration winding system is balanced, in particular calibrated, with respect to the number of active turns of the receiver winding system and/or with respect to the formed surface of the receiver winding system and/or with respect to the geometry of the receiver winding system, due to mechanical milling of the conductor tracks of the at least one calibration winding system.

Furthermore, the invention relates to a positioning sensor having a test structure in the form of a circuit. Test structures may be attached to the evaluation circuit and used to obtain the required milling depth according to the method of the invention.

In one embodiment of the positioning sensor, the at least one transmitting coil and the at least one receiving coil of the positioning sensor are formed as printed coils on a circuit board, in particular as printed coils arranged in planes parallel to one another, which are highly offset. In an alternative embodiment, the transmitting coil is not designed as a printed coil, but as a wound transmitting coil, wherein the at least one receiving coil and the transmitting coil are arranged in planes parallel to each other, which are highly offset.

By realizing the transmitter coil and the receiver coil as printed coils, they are advantageously arranged in a plane directly parallel to the circuit board, i.e. directly adjoining them on the circuit board. In one embodiment, the coil is constructed in a planar, single-layer winding geometry. Thus, a printed circuit can be realized in which no additional costs for manufacturing the receiving winding are incurred. Furthermore, the method according to the invention can be applied particularly easily.

In one embodiment of the positioning sensor, the at least one transmitting coil and the at least one receiving coil are configured coaxially to one another. In one embodiment, the plurality of receiving coils are arranged coaxially with each other and energized in different directions. The at least one transmitter coil may be arranged in a parallel but highly offset plane relative to the receiver coil.

The proposed positioning sensor can be used in inductive measuring devices, for example in positioning devices for detecting metallic objects in walls, ceilings and floors. Alternatively, the positioning sensor may be integrated in or on the machine tool, such as a drilling tool, in order to allow a user of the machine to safely drill holes. For example, the sensor may thus be integrated in a drilling or punching tool or be configured as a module that can be connected to such a tool.

Drawings

The invention is explained in detail in the following description by means of embodiments shown in the drawings. The figures, description and claims contain numerous features in combination. The person skilled in the art can also suitably take the features individually and make up other combinations that are expedient. Like reference symbols in the drawings indicate like elements.

Wherein:

fig. 1 shows in a schematic representation of a sensor geometry of a positioning sensor for positioning a metallic object according to the prior art;

FIG. 2 shows an embodiment of a coil arrangement of a positioning sensor according to the invention in a simplified perspective view;

FIG. 3 shows a top view of a receiving coil and test structure of a positioning sensor in a simplified schematic diagram;

fig. 4 shows an exemplary embodiment of the method according to the present invention.

Detailed Description

Fig. 1 shows a schematic construction of an inductive positioning sensor for positioning a metallic object according to the prior art. Such a positioning sensor has three

coils

12, 14, 16 in its sensor assembly 10. A first transmit coil 12 attached to the first transmitter S1, a second transmit coil 14 attached to the second transmitter S2, and a receive coil 16 attached to the receiver E. Each coil is here shown as a circular line. The three coils 12, 14, 16 are arranged concentrically with respect to a common axis 18. The individual coils 12, 14, 16 have different external dimensions, so that the transmitter coil 12 can be inserted into the transmitter coil 14 coaxially with the axis 18.

The two transmit

coils

12 and 14 are powered by their transmitters S1 and S2 with alternating currents of opposite phases. Thus, the first transmitting coil 12 induces a flux in the receiving coil 16 that is directed opposite to the flux induced in the receiving coil 16 by the second transmitting coil 14. If there is no external metallic object (not shown in detail here) in the vicinity of the sensor assembly 10, the two induced fluxes in the receiving coil 16 compensate each other, so that the receiver E does not detect the received signal in the receiving coil 16 in the ideal case. The flux excited by the

respective transmitter coil

12 or 14 in the receiver coil 16 depends on various parameters, such as the number of turns and geometry of the

coil

12 or 14 and the amplitude of the current fed into the two

transmitter coils

12 or 14 and the mutual phase position of the currents.

In the case of the sensor assembly 10 according to the prior art, these variables should ultimately be optimized in such a way that, in the absence of metallic objects, no flux or as little flux as possible (the described background signal) is excited in the receiving coil 16 in the case of the transmitting

coil

12 or 14 through which the current flows. In the sensor assembly 10 according to fig. 1, the first transmitting coil 12 attached to the first transmitter S1 and the second transmitting coil 14 attached to the second transmitter S1 are arranged coaxially to each other in a common plane. The receive coil 16 is arranged in a plane offset with respect to the two transmit

coils

12 and 14.

Fig. 2 shows an arrangement of a sensor assembly 110 as it is used in a positioning sensor for positioning a metallic object according to the invention. The sensor assembly 110 of the positioning sensor according to fig. 2 has two receiving

coils

112 or 114 which are arranged coaxially to one another in a common plane 126 (formed by an X-axis 122 and a Y-axis 124 in fig. 2) and form a receiving winding system 118. The plane 126 here represents the upper side of the circuit board 126a of the positioning sensor. The receiving coils 112 or 114 of the receiving winding system 118 have a planar, single-layer winding geometry, wherein both receiving

coils

112, 114 are realized on a circuit board 126a in the form of printed circuits (printed coils). The receiving coils 112, 114 are realized in particular in the form of conductor tracks 128 on a circuit board 126 a. The transmit coil 116 is located offset in the direction of the z-axis 120 by a distance relative to a common plane 126 of the receive winding system 118, which is likewise arranged coaxially with the receive coil 112 or the receive coil 114. The transmitter coil 116 is likewise produced as a circuit (printed coil) composed of conductor tracks 128, which are printed in particular onto the rear-side surface of the circuit board 126 a. Windings 117 of transmit coil 116 are located above or below plane 126 of circuit board 126a by a determined, predefined distance along the z-axis. Sensor assembly 110 likewise represents an inductive compensation sensor.

In the schematic of fig. 2, Z-axis 120 is shown extending relative to X-axis 122 and Y-axis 124 for better visibility. Furthermore, for a better view of the cross section in fig. 2, one segment of the

coils

112, 114, 116 is each taken.

The winding 115 of the receiving coil 114 is wound in the clockwise direction in the embodiment shown, while the further outer winding 113 of the receiving coil 112 is wound in the counter-clockwise direction. By properly sizing the number of turns of windings 113, 115 and the winding radius, it can be achieved that if no metallic object (not shown in detail here) is present in the vicinity of the positioning sensor, the voltages induced in the two receiving

coils

112, 114 of the sensor assembly 110 of the sensor system exactly cancel each other due to their opposite signs. However, this compensation is only applicable to a predefined, well-defined position of the transmit coil 116. If the position of the transmitting coil 116 changes relative to a pre-calculated position, for example due to tolerances during the production of the

coils

112, 114, 116 or during the mechanical sensor installation, the resulting error voltage U is induced in the receiving coils 112, 114 _F 。

According to the invention, in the positioning sensor, that is to say in the sensor arrangement 110 shown, the calibration winding system 130 of the receiving winding system 118 is provided in order to balance the voltages U induced in the receiving coils 112, 114 of the receiving winding system 118, wherein at least one calibration winding system 130 is balanced by mechanical milling of the conductor tracks 128 of the at least one calibration winding system 130, that is to say in particular the number of active turns of the receiving winding system 118 is changed and/or the geometry of the receiving winding system 118 is modified in such a way that the total magnetic flux generated through the windings 113, 115 disappears or at least almost disappears if no object to be positioned is located in the vicinity of the positioning sensor.

Furthermore, a test structure 132 (see also fig. 3) for obtaining the required milling depth according to the method of the invention (see fig. 4) is located on the surface of the circuit board 126 a.

The again strongly simplified illustration of fig. 3 serves the purpose of illustrating the method according to the invention. Fig. 3 shows a schematic representation of the schematic arrangement of the receiving

coils

112, 114 with the associated windings 113, 115 in a top view onto the circuit board 126a, i.e. corresponding to the X-Y plane 126 of fig. 2. The transmit coil 116 is not shown in fig. 3. Further, a test structure 132 is shown in fig. 3.

The two receive

coils

112 or 114 are arranged in an X-Y plane 126. The detection voltage is tapped between the two external terminals a and B of the two receiving

coils

112, 114 and is further processed in an evaluation circuit of a measuring device associated with the position sensor. The inner winding 115 of the receiving coil 114 illustrated in fig. 3, depending on the production of the position sensor, is electrically connected to the outer winding 113 of the receiving coil 112 at different locations (designated P1 to P8) via the conductor tracks 128 of the calibration winding system 130. In the context of the calibration positioning sensor, the conductor tracks 128 of the calibration winding system 130 are interrupted at 7 out of 8 positions (P1 to P8), so that a defined receiving winding system 118 results. For example, the radius and the number of turns of the receiving winding system 118 can be dimensioned such that, if the ideal, i.e. theoretically calculated, arrangement of the transmitting coil 116 and the receiving coils 112, 114 remains electrically connected only at the point P5 (i.e. the conductor tracks 128 (electrical contact) are interrupted at the points P1 to P4 and P6 to P8), a mutual compensation of the voltages measured between the points a and B in the absence of metallic objects can be achieved. However, for example, in the case of a maintenance of the electrical connection at the position P1, three complete windings (winding 115) with a smaller radius in the clockwise direction and four windings (winding 113) with a larger radius in the counterclockwise direction are thus obtained in total between points a and B. With the electrical connection maintained at position P5, then effectively 2.5 windings in the clockwise direction and 3.5 windings in the counterclockwise direction are obtained. Since the voltage induced in the winding 113 of the receiving coil 112 has a different amplitude and opposite sign from the voltage induced in the conductor loop of the receiving coil 114, the voltage measured between points a and B can vary depending on the location of the electrical connection that has been maintained. By changing the position to be held, fine tuning of the compensation assembly of the positioning sensor device consisting of three coils can thereby be achieved.

In particular in this embodiment, the effective number of turns of the two oppositely oriented receiving

coils

112, 114 of the receiving winding system 118 varies and is adapted to the respective requirements. Within the scope of the method according to the invention (see fig. 4), therefore, the incorrect positioning of the transmitting coil 116, which is not shown in detail in fig. 3, and the accompanying error voltage U of the inductive sensor due to manufacturing tolerances, can be eliminated or compensated for by a subsequent balancing process _F 。

The test structure 132 shown in fig. 2 and 3 is used to obtain the required milling depth (see method step 204) for carrying out the method according to the invention, i.e. in particular before the method step of mechanically milling the conductor tracks 128 of the calibration winding system 130 is carried out. The test structure here consists of a circuit comprising conductor tracks 128. The conductor track 128 is grounded on one side ("GND") and on the other side is attached to the potential of "VCC" in a high-impedance manner via a resistor 134. In this embodiment, resistor 134 has a value of 1 k Ω to 10 k Ω. In this way, since the contact point 136 is grounded (potential GND) with low impedance via the conductor track 128 to be milled, the conductor track 128 has a vanishing potential at the contact point 136 before the milling for obtaining the desired milling depth is performed. Once the conductor tracks 128 are milled through at the milling locations 138, the resistance dominates and the potential at the contact locations 136 is set to VCC. By measuring the potential at contact point 136, a complete penetration of conductor track 128 can therefore be detected due to the increase in potential from GND to VCC.

It should be noted that the positioning sensor for positioning a metal object according to the present invention is not limited to the embodiment shown in the drawings. In particular, the receive winding system 118 of the positioning sensor according to the present invention is not limited to the use of two receive

coils

112, 114 and/or the use of 8 calibration winding systems.

Fig. 4 shows an exemplary embodiment of the method according to the invention by means of a method diagram. In a method step 200, a test structure 132 for obtaining a desired milling depth is first attached to an evaluation circuit (not shown in detail here). With a voltage VCC (equivalent to: current) applied across the test structure 132, an evaluation circuit is used for the electrical contact of the test structure 132. Furthermore, the evaluation circuit serves to detect a voltage applied to the contact locations 136 of the test structure 132 (see fig. 3).

In a method step 202, a milling tool (not shown in detail here) is then positioned at the location of the test structure 132, i.e. at the defined milling location 138 of the test structure 132, in particular at the conductor tracks 128 of the test structure 132. Subsequently, in a method step 204 preceding the method step of mechanical milling of the conductor tracks 128 of the calibration winding system 130, the desired milling depth is obtained by mechanical milling of the test structures 132 arranged on the circuit board 126 a. For this purpose, in particular, in method step 206, a minimum milling depth (empirical or construction-dependent) is initially set. Subsequently, in method step 208, the milling depth is iteratively increased, and in method step 210, milling is performed into conductor tracks 128 of test structure 132 by means of a milling tool until the milling depth is now set. If the conductor tracks 128 of the test structure 132 are completely milled through, i.e. the desired milling depth is reached, a voltage change (see fig. 3) and/or a current change is detected at the contact points 136 of the test structure 132 by means of the evaluation circuit (it is determined in step 212 that the desired milling depth has been reached: yes/no "). Next, the loop of iterative method steps 208, 210 is exited. The current settings for the desired milling depth are then stored (method step 214).

With the current value now or the current setting now for the desired milling depth, in step 216 the milling tool is positioned at the position of the conductor tracks 128 to be milled of the calibration winding system 130, that is to say P1 to P8. Finally, in a method step 218, the conductor tracks are milled to the desired milling depth, if necessary with the addition of a tolerance value.

The other conductor tracks 128 can then be executed with the same settings as the required milling depth, in particular iteratively at 7 out of 8 positions P1 to P8. Alternatively, the method may again be performed on another test structure 132 of the positioning sensor.

In this way, the calibration of the inductive position sensor is performed according to the invention, wherein the voltage U induced in the receiving coil of the receiving winding system 118 is balanced by switching off at least one calibration winding system 130 of the receiving winding system 118, wherein the at least one calibration winding system 130 is switched off in a method step by means of mechanical milling of the conductor tracks 128 of the at least one calibration winding system 130 (method step 218).

Claims

1. Method for calibrating an inductive position sensor having at least one transmitter coil (116) and at least one receiver winding system (118), which are formed on a circuit board (126 a) of the inductive position sensor in the form of conductor tracks (128), wherein a voltage U induced in the receiver coils (112, 114) of the receiver winding system (118) is balanced by switching off at least one calibration winding system (130) of the receiver winding system (118), characterized in that the at least one calibration winding system (130) is switched off in a method step 218 by means of mechanical milling of the conductor tracks (128) of the at least one calibration winding system (130).

2. The method according to claim 1, characterized in that in a method step 204 preceding a method step 218 of mechanical milling of the conductor tracks (128) of the calibration winding system (130), the required milling depth is obtained by mechanical milling of a test structure (132) provided on the circuit board (126 a).

3. The method according to claim 2, characterized in that the test structure (132) is implemented by a circuit, wherein the test structure (132) is operated by means of an evaluation circuit during the execution of the method step 204 for obtaining the required milling depth.

4. A method according to any of claims 2-3, characterized in that in a method step 202 before the method step 204 for obtaining the required milling depth, a milling tool is positioned onto the test structure (132).

5. A method according to any of claims 2-3, characterized in that during method step 204 for obtaining a desired milling depth, a minimum milling depth is set first and then the milling depth is iteratively increased until the desired milling depth is reached.

6. A method according to claim 3, characterized in that the desired milling depth is reached during the execution of the method step 204 for obtaining the desired milling depth when a voltage change and/or a current change is detected on the test structure (132) by means of the evaluation circuit.

7. A method according to any one of claims 2 to 3, characterized in that in the method step of mechanical milling of the conductor tracks of the calibration winding system (130), first a milling tool is positioned at the position (P1-P8) of the conductor tracks (128) of the calibration winding system (130) to be milled and then the conductor tracks (128) are milled to the desired milling depth.

8. A positioning sensor for positioning a metallic object, having at least one transmitting coil (116) and at least one receiving winding system (118) which are inductively coupled to one another and are designed on a circuit board (126 a) of the positioning sensor in the form of conductor tracks (128), characterized by at least one calibration winding system (130) of the receiving winding system (118) for balancing a voltage U induced in the receiving coils (112, 114) of the receiving winding system (118), wherein the at least one calibration winding system (130) is balanced in terms of an effective number of turns in relation to the receiving winding system (118) and/or in terms of a formed face in relation to the receiving winding system (118) and/or in terms of a geometry in relation to the receiving winding system (118) due to mechanical milling of the conductor tracks (128) of the at least one calibration winding system (130).

9. The positioning sensor of claim 8, characterized in that the positioning sensor comprises at least one test structure (132) in the form of an electrical circuit.

10. The positioning sensor according to any one of claims 8 to 9, characterized in that the at least one transmitting coil (116) and the receiving coil (112, 114) are configured as printed coils on the circuit board (126 a).

11. The positioning sensor according to claim 8, characterized in that the at least one calibration winding system (130) is calibrated as a result of mechanical milling of the conductor tracks (128) of the at least one calibration winding system (130) with respect to the effective number of turns of the receiving winding system (118) and/or with respect to the formed face of the receiving winding system (118) and/or with respect to the geometry of the receiving winding system (118).

12. The positioning sensor according to claim 10, characterized in that the at least one transmitting coil (116) and the receiving coil (112, 114) are constructed on the circuit board (126 a) as printed coils arranged in mutually parallel, highly offset planes.