FR3149377A1 - Offset compensated inductive position sensor - Google Patents

Abstract

Inductive position sensor with offset compensation The invention relates to an inductive position sensor comprising: a mobile target (3) adapted to modify an electromagnetic field; a fixed circuit plate (5) having a loopback zone (R) for the magnetic field in which a primary winding (7) is arranged surrounding two secondary windings (8, 9); a current generator (11) for creating an inductive coupling modulated by the position of the target; a detector (13) of the linear or angular position of the target; and a system for balancing the coupling between the primary winding (7) and the secondary windings (8, 9) comprising at least one conductive compensation zone (Z) arranged in the loopback zone (R) for compensating the measurement offset. Figure for the abstract: Fig. 4.

Description

Offset compensated inductive position sensor

The present invention relates to the technical field of inductive position sensors by eddy current coupling.

The present invention finds applications for determining the linear or angular position of moving parts for example in motor vehicles, engines or machine tools.

The state of the art has proposed various solutions of inductive sensors by eddy current coupling to measure the position of a mobile along a linear or angular trajectory.

To determine the linear position of a moving object, US patent 6,483,295 describes a position sensor comprising a target mounted so as to move relative to a fixed printed circuit board or plate on which tracks configured to form windings or coils are arranged. Thus, the circuit board comprises a primary winding connected to an alternating current generator for generating a magnetic field when current flows in said primary winding. This primary winding surrounds secondary windings. The magnetic field thus created is perceived by the secondary windings and induces a current in said secondary windings.

The target is made of a conductive material to allow the flow of eddy currents. This target is moved linearly relative to the primary winding and the secondary windings. The inductive coupling between the primary winding and the secondary windings is modulated by the position of the target. The geometries of the secondary windings are chosen so that the induced signals delivered by the secondary windings depend on the position of the target. A detector connected to the secondary windings makes it possible, from the induced signals from the secondary windings, to determine the position of the target.

In an optimal configuration, the coupling between the primary winding and the secondary windings in the absence of the target is zero. The non-zero value of this coupling in the absence of the target is called direct coupling or measurement offset. However, it appears that at least one of the secondary windings does not have a symmetrical shape relative to the ends of the primary winding. This asymmetry in the configuration of a secondary winding leads to the appearance of the measurement offset signal. To overcome this drawback, US patent 6,483,295 proposes reducing the size of a secondary winding at the ends of the primary winding. This solution has the drawback of reducing the linear measurement portion for a constant size of the sensor.

In the field of angular position measurement sensors, patent FR 3 023 611 proposes, in order to remedy the problem of the concentration of field lines at the ends of the primary winding, to produce the secondary windings in particular by tracks delimiting complete meshes. This solution has the disadvantage of increasing the size of the circuit whose primary winding surrounds the two secondary windings.

Similarly, GB 2 167 563 describes a position or speed sensor by eddy current coupling. According to embodiments, this document proposes to produce the target in several parts in order to obtain a linear signal or to implement several secondary windings to obtain a univocal signal over the entire stroke. Such solutions do not allow the measurement offset to be compensated.

US Patent 5,886,519 also describes a position sensor proposing in particular to compensate for manufacturing tolerances or other constraints tending to create a signal offset, to modify the size and shape of the secondary windings or the distance between the primary winding and the secondary windings which is at least one period. This solution results in an increase in the size of the sensor.

It is apparent from the prior art that various technical solutions aim to minimize the measurement offset by changing the geometric configurations of the windings. It should be noted that the measurement offset of a given winding configuration can be obtained by testing or by simulation. However, it turns out that geometric changes have several drawbacks. The first concerns their sensitivity because a displacement of the tracks by a few hundredths of a mm causes a large variation in the measurement offset. Optimizing the measurement offset by moving the tracks therefore requires very good resolution during the simulation. Furthermore, their implementation requires a complete resumption of the configuration of the windings including a displacement of the vias (connection holes). There is also a risk that the configuration resulting from an automated optimization is not physically achievable, in particular while respecting the insulation distances. Finally, optimization cannot be carried out by simple successive tests on a given printed circuit board.

The present invention therefore aims to remedy the drawbacks of the prior art by proposing a new inductive sensor for determining the linear or angular position of a moving part, making it possible to reduce the measurement offset independently of changes in the configuration of the windings.

To achieve such an objective, the inductive position sensor according to the invention, for determining the position of a moving object along a linear or rotating trajectory, comprises:
- a moving target along the trajectory adapted to modify an electromagnetic field;
- a fixed circuit plate extending in relation to the trajectory of the target and having a loopback zone for the magnetic field in which are arranged at least a first and a second secondary winding and a primary winding surrounding the two secondary windings, the first secondary winding being adapted to generate a first signal upon detection of a target while the second secondary winding is adapted to generate a second signal upon detection of a target, this second signal being offset relative to the first signal;
- a current generator for the primary winding or the secondary windings to create between the primary winding and the secondary windings an inductive coupling modulated by the position of the target;
- a detector of the linear or angular position of the target from the induced signals from the secondary windings or the primary winding;
- and a coupling balancing system between the primary winding and the secondary windings making it possible to compensate for a measurement offset, this coupling balancing system comprising at least one conductive compensation zone arranged in the loopback zone.

According to an implementation variant, the looping zone extends outside the primary winding along a peripheral strip and at least one conductive compensation zone is provided in this peripheral strip.

Typically, the loopback zone extends outside the primary winding in a peripheral band of width equal to ½ the width of the primary winding.

According to one embodiment, the looping zone extends outside the primary winding along a peripheral strip delimited between the primary winding and a ground plane.

According to another embodiment, the looping zone extends outside the primary winding along a peripheral strip delimited between the primary winding and a ground plane and at least one conductive compensation zone is arranged in this peripheral strip while being connected to the ground plane.

According to another implementation variant, the looping zone extends inside the primary winding by an internal zone and at least one conductive compensation zone is arranged in this internal zone.

Advantageously, the first secondary winding and the second secondary winding each comprise meshes oriented positively and negatively depending on the direction of flow of the current flowing in these meshes and at least one conductive compensation zone is positioned to reduce the contribution to the signal of a positive or negative mesh of at least one secondary winding.

According to an exemplary embodiment, the first secondary winding and the second secondary winding comprise meshes oriented positively and negatively depending on the direction of flow of the current flowing in these meshes and at least one conductive compensation zone is positioned to reduce the contribution on the one hand to the first signal of a positive or negative mesh of the first secondary winding and on the other hand, to the second signal of a positive mesh or a negative mesh of the second secondary winding.

According to another exemplary embodiment, the sensor comprises several conductive compensation zones.

For example, the sensor has several symmetrically arranged conductive compensation zones.

Advantageously, the secondary windings have substantially identical lengths.

Various other features emerge from the description given below with reference to the attached drawings which show, by way of non-limiting examples, embodiments of the subject of the invention.

There is a schematic view of an exemplary embodiment of a position sensor of the prior art, of the rotary type.

There is an example of a rotary type position sensor and more particularly illustrating the positively oriented meshes of a sinusoidal secondary winding, depending on the direction of current flow.

There is an example of a rotary type position sensor and more particularly illustrating the negatively oriented meshes of a sinusoidal secondary winding, depending on the direction of current flow.

There is an example of a rotary type position sensor and more particularly illustrating the positively oriented meshes of a cosine secondary winding, depending on the direction of current flow.

There is an example of a rotary type position sensor and more particularly illustrating the negatively oriented meshes of a cosine secondary winding, depending on the direction of current flow.

There is a schematic view of an embodiment of a position sensor according to the invention of the rotary type implementing a conductive compensation zone positioned inside the primary winding to reduce the contribution to the signal of a positive mesh of a sinusoidal secondary winding.

There is seen in longitudinal section taken approximately along lines AA of the .

There is a schematic view of another embodiment of a position sensor according to the invention of the rotary type implementing a conductive compensation zone positioned inside the primary winding to reduce the contribution to the signal of a positive mesh of a cosine secondary winding.

There is a schematic view of an alternative embodiment of a position sensor according to the invention of the rotary type implementing a conductive compensation zone positioned outside the primary winding to reduce the contribution to the signal of a positive mesh of a cosine secondary winding.

There is a schematic view of an alternative embodiment of a position sensor according to the invention of the rotary type implementing a conductive compensation zone positioned outside the primary winding while being connected to the ground plane, to reduce the contribution to the signal of a positive mesh of a cosine secondary winding.

There is a schematic view of another embodiment of a position sensor according to the invention of the rotary type implementing a conductive compensation zone positioned inside the primary winding to reduce the contribution to the signal of a positive mesh of a cosine secondary winding and to the signal of a positive mesh of a sinus secondary winding.

There is a schematic view of another embodiment of a position sensor according to the invention of the rotary type implementing a conductive compensation zone positioned inside the primary winding to reduce the contribution to the signal of a positive mesh of a sinusoidal secondary winding and to the signal of a negative mesh of a cosine secondary winding.

There is a schematic view of another embodiment of a position sensor according to the invention of the rotary type implementing four conductive compensation zones positioned inside the primary winding in a symmetrical manner to reduce the contributions to the signal of a positive mesh of a sinusoidal secondary winding and to the signal of a positive mesh of a cosine secondary winding.

There is a schematic view of another embodiment of a position sensor according to the invention of the linear type implementing four conductive compensation zones positioned inside the primary winding but outside the secondary windings.

As is more precisely apparent from the figures, the subject of the invention relates to a position sensor 1 for a mobile in the general sense not shown and whose position is to be determined along an angular trajectory F according to the examples illustrated in FIGS. 4 to 11 and a linear trajectory F according to the example illustrated in . Conventionally, a position sensor 1 comprises a stator part 2 and a target 3 mounted to move along the trajectory F. Thus, the target 3 is driven by the moving part or is arranged on the moving part whose position is to be determined. The target 3 is made of an electrically conductive material such as metal, to allow the circulation of eddy currents.

In reference to the , the stator part 2 of the position sensor 1 of the rotary type is produced over the entire circumference corresponding to the travel of the mobile, i.e. of the target 3. The stator part 2 comprises a printed circuit board or plate 5 which is fixedly mounted relative to the target 3. In a known manner, the circuit board 5 comprises a primary winding 7 surrounding at least a first secondary winding 8 and a second secondary winding 9, magnetically coupled to the primary winding 9. For the rotary type sensor, the primary winding 7 has an external segment 7e of circular shape and an internal segment 7i of circular shape between which the secondary windings 8, 9 are arranged. For the linear type sensor illustrated in FIG. , the primary winding 7 has two main segments 7a extending parallel to each other and to the trajectory F and two end segments 7b extending parallel to each other but perpendicular to the trajectory F.

According to an exemplary embodiment, it should be noted that an electrical ground plane M is provided on one face of the circuit board 5. As is more precisely shown in FIGS. 4 to 12, this electrical ground plane M is provided on the part of the face located outside the primary winding 7 and at a distance from this primary winding 7. It should be noted that it may be provided that the circuit board 5 does not have an electrical ground plane M on one of its faces.

Typically, an alternating current generator 11 is connected to the primary winding 7 to generate a magnetic field when a current flows in said primary winding. The magnetic field thus created is perceived by the secondary windings 8, 9 and induces a voltage in said secondary windings. For example, the current generator 11 delivers a high-frequency alternating current, allowing the establishment of eddy currents in the target 3.

The inductive coupling between the primary winding 7 and the secondary windings 8, 9 is modulated by the position of the target 3. The target 3 modifies the magnetic coupling between the primary winding 7 and the secondary windings 8, 9. The illustrates the loopback zone R for the magnetic field between the primary winding 7 and the secondary windings 8, 9. The loopback of the magnetic field is carried out through the circuit plate 5 in a plane substantially perpendicular to this circuit plate 5. This loopback zone R thus extends inside the primary winding 7 but also outside the primary winding 7 along a peripheral strip B, contiguous to this primary winding 7.

Advantageously, the looping zone R extends outside the primary winding 7 along a peripheral strip B of width equal to ½ of the width l of the primary winding 7. In the case of a rotary sensor, the width l of the primary winding 7 is the radial distance taken between the external segment 7e and the internal segment 7i ( ) whereas in the case of a linear sensor, the width l of the primary winding 7 is the distance taken between the two main segments 7a and perpendicular to the trajectory F ( ).

According to an alternative embodiment for which the ground plane M is present, the looping zone R extends outside the primary winding 7 along the peripheral strip B delimited between the primary winding 7 and the ground plane M. In other words, the looping zone R extends outside the primary winding 7 to the edge delimiting the ground plane M.

These secondary windings 8, 9 are connected to a detector 13 which, by measuring the electrical voltages induced at the terminals of the secondary windings 8, 9, makes it possible to deduce the precise position of the target 3. Consequently, the detector 13 makes it possible to determine the position of the mobile.

According to this configuration, the primary winding 7 is designated as the transmitter winding while the secondary windings 8, 9 are designated as the receiver windings. It should be noted that a reverse operation can be envisaged for which the current generator 11 is connected to the secondary windings 8, 9 which are transmitters while the primary winding 7 is the receiver and to which the detector 13 is connected which, from the phase of the induced signal, makes it possible to deduce the precise position of the target 3.

For the sake of clarity of the drawings, the inputs and outputs of the windings 7, 8, 9 are not shown. Similarly, each winding is represented by a forward track and a return track forming a loop or a winding. Of course, each winding 7, 8, 9 may have several forward tracks and several return tracks. The forward track and the return track of each winding have suitable shapes making it possible to delimit meshes between them.

In a known manner, in the presence of the target 3 in the measurement window, the secondary windings 8, 9 placed near said target 3 see a lower quantity of flux of the magnetic field than if the target 3 were absent. Each secondary winding 8, 9 is generally made up of meshes of opposite orientations so that when the target 3 moves above one then the other of these meshes, the secondary winding sees, compared to a zero average value, a relative increase then a relative decrease in the quantity of flux of the magnetic field passing through it.

According to a known preferred embodiment, the inductive sensor implements two secondary windings offset by 90°. According to this example, there is, on the one hand, a first secondary winding 8 having a form of a sine function called "sine" 8 adapted to deliver a sine signal when a target 3 passes through the measurement window and a second secondary winding 9 having a form of a cosine function called "cosine" 9 adapted to deliver a cosine signal when a target 3 passes through the measurement window. The sine/cosine signals which are transmitted to the detector 13 make it possible to determine the precise angular or linear position of the target by calculating the arc tangent. Thus, according to the embodiments illustrated in the drawings, the position sensor 1 comprises two secondary windings 8, 9 offset by 90° (sine and cosine). Of course, the position sensor can have a larger number of secondary windings, such as three secondary windings offset two by two by 120°.

In a conventional manner, the first secondary winding 8 which has the shape of a sine function, is made up of a forward track 8a and a return track 8r delimiting between them positively oriented meshes Ms+ ( ) separated two by two by negatively oriented meshes Ms- ( ), depending on the direction of current flow in these meshes. The second secondary winding 9 which has the form of a cosine function, is made up of a forward track 9a and a return track 9r delimiting between them positively oriented meshes Mc+ ( ) separated two by two by negatively oriented meshes Mc- ( ), depending on the direction of current flow in these meshes.

It should be noted that according to this embodiment, the secondary windings 8, 9 have the exact shapes of the sine and cosine functions respectively. For the rotary type sensor, the secondary windings 8, 9 are arranged in a circular direction for an angular or more precisely rotating trajectory of the target.

According to the example of realization of the illustrating a linear sensor, the forward track 8a and the return track 8r of the first secondary sine winding 8 delimit between them a first mesh and a second mesh. The forward track 9a and the return track 9r of the secondary cosine winding 9 delimit between them a first half-mesh, a central mesh and a second half-mesh. The ends of the forward track 8a and the return track 8r of the first secondary sine winding 8 located near each end segment 7b of the primary winding are positioned at the same location so that the forward track 8a and the return track 8r of the first secondary sine winding 8 have a common mean line Ls. This mean line Ls is parallel to the trajectory F. The forward track 9a and the return track 9r of the second secondary cosine winding 9 are connected, at their ends, by a connecting track 9l extending perpendicular to the trajectory F.

Advantageously, the two secondary windings 8, 9 are arranged so that their two ends are located on two lines perpendicular to the trajectory F and separated by a distance C. Thus, the two secondary windings 8, 9 have a substantially identical length C, taken in a direction parallel to the trajectory F and corresponding to the measurement window of the position sensor 1. It should be noted that the two secondary windings 8, 9 also have a substantially identical length C for the case of a rotary sensor.

As recalled in the preamble of the present patent application, the coupling between the primary winding 7 and the secondary windings 8, 9, in the absence of the target 3, is zero if the configuration or design of the windings is optimal. Given the difficulty in achieving such a configuration, the coupling between the primary winding 7 and the secondary windings 8, 9, in the absence of the target 3, leads to a measurement offset.

According to the invention, the inductive position sensor 1 comprises a system for balancing the coupling between the primary winding 7 and the secondary windings 8, 9, adapted to compensate for the measurement offset. According to the invention, the coupling balancing system comprises at least one conductive compensation zone Z arranged in the loopback zone R. In other words, the inductive position sensor 1 comprises one or more conductive compensation zones Z arranged so as to compensate for the measurement offset.

Each conductive compensation zone Z corresponds to a surface of an electrically conductive material arranged on or in the circuit board 5. In the exemplary embodiment illustrated in , the conductive compensation zone Z is arranged on the upper face of the circuit plate 5, in the same plane as that in which the primary winding 7 and the ground plane M are arranged. Of course, the conductive compensation zone Z can be arranged on a different face or at the level of an intermediate layer of the circuit plate 5.

The presence of one or more conductive compensation zones Z in the loopback zone R has an impact on the measurement offset because the coupling between the primary winding 7 and the secondary windings 8, 9 is weakened in the area near each of these conductive compensation zones Z. The size and position of the conductive compensation zone(s) Z are optimized to minimize the measurement offset. Such optimization can be carried out using numerical simulations or using positioning tests of conductive compensation zones with different or different surfaces. The conductive compensation zone(s) Z are arranged in the loopback zone R without being in contact with the primary winding and the secondary windings. The conductive compensation zone(s) Z are therefore arranged near the primary winding 7 and the secondary windings 8, 9, being superimposed or not with respect to these windings. In the example illustrated in , the conductive compensation zone Z is arranged by being superimposed on the secondary windings 8, 9.

It must therefore be understood that the conductive compensation zone(s) Z are arranged outside the primary winding 7 and/or inside the primary winding 7 since the loopback zone R extends over the entire zone located inside the primary winding 7 but also over the entire peripheral strip B externally bordering the primary winding 7. Similarly, at least one conductive compensation zone Z is positioned to reduce the contribution to the signal of a positive and/or negative mesh of at least one secondary winding 8, 9.

According to an alternative embodiment, at least one conductive compensation zone Z is provided in the peripheral strip B, as illustrated in FIGS. 7 and 8. In the example illustrated in , a conductive compensation zone Z is provided in the peripheral strip B, being partly superimposed on the primary winding 7. In the example illustrated in , a conductive compensation zone Z is arranged in the peripheral strip B by being connected to the ground plane M. In other words, the ground plane M extends locally in the peripheral strip B in the direction of the primary winding 7, to form a conductive compensation zone Z. It should be noted that in the examples illustrated in FIGS. 7 and 8, the conductive compensation zone Z is arranged to reduce the contribution to the signal of a positive mesh of the cosine secondary winding 9 since it is arranged near a positive mesh of the cosine secondary winding 9. Of course, the conductive compensation zone Z can be arranged to reduce the contribution to the signal of a positive mesh of the sinus secondary winding and/or of a negative mesh of the sinus and/or cosine secondary winding.

According to another variant embodiment, at least one conductive compensation zone Z is arranged in the part of the loopback zone R located inside the primary winding 7. Inside this internal zone of the primary winding, all the positions of the conductive compensation zone(s) Z relative to the meshes of the secondary windings 8, 9 are possible in order to compensate for the measurement offset.

Thus, at least one conductive compensation zone Z can be positioned to reduce the contribution to the signal of a positive or negative mesh of the first secondary winding 8. Similarly, at least one conductive compensation zone Z can be positioned to reduce the contribution to the signal of a positive or negative mesh of the second secondary winding 9. According to another variant embodiment, at least one conductive compensation zone Z is positioned to reduce the contribution on the one hand to the first signal of a positive or negative mesh of the first secondary winding 8 and on the other hand, to the second signal of a positive mesh or a negative mesh of the second secondary winding 9.

According to the example of realization illustrated in the , a conductive compensation zone Z is positioned to reduce the contribution to the signal of a positive mesh Ms+ of the sinusoidal secondary winding. This conductive compensation zone Z is positioned in a positive mesh Ms+ of the sinusoidal secondary winding, near the part of the outward track 8a located closest to the external segment 7e of the primary winding 7.

In the example embodiment illustrated in the , a conductive compensation zone Z is positioned inside the primary winding to reduce the contribution to the signal of a positive mesh Ms+ of a cosine secondary winding. This conductive compensation zone Z is positioned in a positive mesh Ms+ of the cosine secondary winding 9a, near the part of the outward track 9a located closest to the external segment 7e of the primary winding 7.

According to the example of realization illustrated in the , a conductive compensation zone Z is positioned inside the primary winding to reduce the contribution to the signal of a positive mesh Mc+ of the cosine 9 secondary winding and to the signal of a positive mesh Ms+ of the sine 8 secondary winding. This conductive compensation zone Z is positioned in the common zone of the positive mesh Mc+ of the cosine 9 secondary winding and the positive mesh Ms+ of the sine 8 secondary winding.

According to the example of realization illustrated in the , a Z compensation conductive zone is positioned inside the primary winding to reduce the contribution to the signal of a positive mesh of the secondary winding sine 8 and to the signal of a negative mesh of the secondary winding cosine 9. This Z compensation conductive zone is positioned in the common zone of a positive mesh of the secondary winding sine 8 and of a negative mesh of the secondary winding cosine 9.

In the preceding examples, only one conductive compensation zone Z is provided. Of course, several conductive compensation zones can be provided. The illustrates an embodiment implementing four Z-compensation conductive zones positioned inside the primary winding in a symmetrical manner to reduce the contributions to the signal of a positive mesh of the sine secondary winding and to the signal of a positive mesh of the cosine secondary winding. These Z-compensation conductive zones have a 90° offset by being positioned in the common area of the positive mesh Mc+ of the cosine secondary winding 9 and the positive mesh Ms+ of the sine secondary winding 8.

There illustrates another embodiment variant implementing several Z-compensation conductive zones for a linear-type position sensor. According to this example, four Z-compensation conductive zones are positioned inside the primary winding 7 but outside the secondary windings 8, 9. More precisely, two Z-compensation conductive zones are arranged near each connecting track 9l, between this connecting track 9l and the end segment 7b adjacent to the primary winding 7.

The subject of the invention makes it possible to minimize the measurement offset by optimizing the size and position of the Z compensation conductive zone(s). Such optimization carried out by numerical simulation or by tests is simple and rapid. Typically, this optimization, which is characterized by the implementation of one or more Z compensation conductive zones, leads to a reduction in the measurement offset of at least 50% compared to a sensor not comprising such Z compensation conductive zones.

Claims (11)

Inductive position sensor for determining the position of a moving object along a linear or rotating trajectory (F), comprising:
- a target (3) moving along the trajectory adapted to modify an electromagnetic field;
- a fixed circuit plate (5) extending in relation to the trajectory of the target and having a loopback zone (R) for the magnetic field in which are arranged at least a first and a second secondary winding (8, 9) and a primary winding (7) surrounding the two secondary windings (8, 9), the first secondary winding (8) being adapted to generate a first signal upon detection of a target while the second secondary winding is adapted to generate a second signal upon detection of a target, this second signal being offset relative to the first signal;
- a current generator (11) for the primary winding or the secondary windings to create between the primary winding (7) and the secondary windings (8, 9) an inductive coupling modulated by the position of the target;
- a detector (13) of the linear or angular position of the target from the induced signals from the secondary windings or the primary winding;
- and a coupling balancing system between the primary winding (7) and the secondary windings (8, 9) making it possible to compensate for a measurement offset, the coupling balancing system comprising at least one conductive compensation zone (Z) arranged in the loopback zone (R). Sensor according to claim 1, characterized in that the looping zone (R) extends outside the primary winding along a peripheral strip (B) and in that at least one conductive compensation zone (Z) is provided in this peripheral strip. Sensor according to claims 1 or 2, characterized in that the looping zone (R) extends outside the primary winding along a peripheral strip (B) of width equal to ½ the width of the primary winding. Sensor according to one of claims 1 to 3, characterized in that the looping zone (R) extends outside the primary winding along a peripheral strip (B) delimited between the primary winding and a ground plane (M). Sensor according to one of claims 1 to 4, characterized in that the looping zone (R) extends outside the primary winding along a peripheral strip (B) delimited between the primary winding and a ground plane (M) and in that at least one conductive compensation zone (Z) is arranged in this peripheral strip (B) while being connected to the ground plane (M). Sensor according to one of claims 1 to 5, characterized in that the loopback zone (R) extends inside the primary winding by an internal zone and in that at least one conductive compensation zone (Z) is arranged in this internal zone. Sensor according to one of the preceding claims, characterized in that the first secondary winding (8) and the second secondary winding (9) each comprise meshes oriented positively and negatively depending on the direction of flow of the current flowing in these meshes and in that at least one conductive compensation zone (Z) is positioned to reduce the contribution to the signal of a positive or negative mesh of at least one secondary winding. Sensor according to one of the preceding claims, characterized in that the first secondary winding (8) and the second secondary winding (9) comprise meshes oriented positively and negatively depending on the direction of flow of the current flowing in these meshes and in that at least one conductive compensation zone (Z) is positioned to reduce the contribution on the one hand to the first signal of a positive or negative mesh of the first secondary winding (8) and on the other hand, to the second signal of a positive mesh or a negative mesh of the second secondary winding (9). Sensor according to one of the preceding claims, characterized in that it comprises several conductive compensation zones (Z). Sensor according to the preceding claim, characterized in that it comprises several conductive compensation zones (Z) arranged symmetrically. Sensor according to one of the preceding claims, characterized in that the secondary windings (8, 9) have substantially identical lengths (L).