Magnetic flux concentrators

Abstract

The present disclosure relates to magnetic flux concentrators. There is disclosed a magnetic flux concentrator, including a first element (4a) and a second element (4b) each having at least two magnetic flux concentrating limbs (2a, 2b). The first and second elements are arranged such that each magnetic flux concentrating limb (2a) is aligned with, and spaced from, a corresponding magnetic flux concentrating limb (2b) to create a concentrated magnetic flux region. The disclosure extends to, inter alia, a device including the magnetic flux concentrator and a method of operating such a device.

Description

[0001] Magnetic Flux Concentrators

[0002] Field of the invention

[0003] The present invention relates to magnetic flux concentrators, magnetic sensor devices comprising the magnetic flux concentrators and methods of operating the same; and kits for assembling said magnetic flux concentrators; particularly for use in magnetic sensing arrays.

[0004] Background to the invention

[0005] It is known to enhance the sensitivity of a magnetic sensor using a magnetic flux concentrator (MFC). Magnetic flux concentration, also known as magnetic magnification, is achieved by increasing the density of magnetic flux lines.

[0006] In recent years, as magnetic sensors have improved, particularly with the introduction of Tunnelling Magnetoresistance (TMR) sensor technology, many new applications for magnetic sensing have emerged, e.g. from medical diagnostics to industrial testing. It is becoming more important for magnetic sensing applications to reguire multiple channels of measurement, in the form of magnetic sensor arrays.

[0007] Tunnel magnetoresistance (TMR) is a guantum mechanical effect that can be exploited by magnetic sensors called TMR sensors. This effect occurs in structures called magnetic tunnel junctions (MTJs) which typically include two ferromagnetic metal layers separated by a thin insulating barrier. The insulating barrier decouples the ferromagnetic metal layers and reguires the electrons in the decoupled layers to exploit guantum tunnelling to move between them. In an MTJ, one of the ferromagnetic metal layers (i.e. the ‘fixed’ layer) has a magnetic moment with a fixed orientation and the other layer (i.e. the ‘free’ layer) has a magnetic moment that can change orientation freely. When the MTJ is exposed to a magnetic field, the orientation of the magnetic moment in the ‘free’ layer changes and the relative alignment of the magnetic moments in the two ferromagnetic metal layers increases or decreases the resistance through the layers, which results in a change in tunnelling current that can be measured. This change can be indicative of the sensed magnetic field.

[0008] Traditional magnetic flux concentrators are bulky and occupy a large area when arranged in arrays, which limits the miniaturisation of magnetic sensing devices and limits the spatial resolution that can be achieved with sensor arrays.

[0009] It is an aim of the present invention to provide magnetic flux concentrators which address at least some of the above problems.

[0010] Summary of the invention

[0011] According to a first aspect of the present invention there is provided a magnetic flux concentrator, comprising: a first element having at least two magnetic flux concentrating limbs; and a second element having at least two magnetic flux concentrating limbs, wherein the first and second elements are arranged such that each magnetic flux concentrating limb is aligned with, and spaced from, a corresponding magnetic flux concentrating limb to create a concentrated magnetic flux region. The invention extends to a magnetic sensor device, comprising the magnetic flux concentrator of the first aspect and one or more magnetic sensors or magnetic sensor elements located at each concentrated magnetic flux region. The invention further extends to a method of operating such a magnetic sensor device; comprising exposing the magnetic sensor device to a magnetic field and sensing the magnetic field at each of the one or more magnetic sensors or magnetic sensor elements.

[0012] Thus, the invention provides a magnetic flux concentrator suitable for use in magnetic sensing applications. Each element has one or more magnetic flux concentrating limbs which can be aligned with corresponding magnetic flux concentrating limbs (e.g. of other elements) to allow a plurality of concentrated magnetic flux regions to be created, for example, for concentrating magnetic flux in a magnetic sensor array. The applicant has found that magnetic flux concentrators embodying the invention occupy a smaller footprint without sacrificing magnetic gain at the concentrated magnetic flux regions. This is particularly useful for applications requiring miniaturised sensor devices with high sensitivity. Embodiments of the invention may achieve magnetic flux concentration without having to sacrifice small device footprint. Thus, embodiments of the invention are particularly suitable for applications which require the use of compact sensor arrays.

[0013] Furthermore, in some embodiments, the present invention may achieve improved magnetic gain when compared with traditional single-channel magnetic flux concentrators. The modularity of the individual elements of the magnetic flux concentrator provides improved flexibility of design and scalability and allows magnetic flux concentrators to be built up into arrays of different sizes and shapes to suit different purposes and magnetic sensing applications. Magnetic flux concentrators in accordance with the invention, thus, may help to improve sensitivity for compact and dense arrays of magnetic sensors for recording high resolution magnetic signals. For example, mapping high spatial density magnetic fields requires dense magnetic sensor arrays.

[0014] When a magnetic flux concentrating limb is aligned with, and spaced from, a corresponding magnetic flux concentrating limb a concentrated magnetic flux region is created. These magnetic flux concentrating limbs may have a similar shape. In a set of embodiments, a magnetic flux concentrating limb has substantially the same shape as the magnetic flux concentrating limb that it corresponds with. The magnetic flux concentrating limbs creating a concentrated magnetic flux region may be considered a pair of magnetic flux concentrating limbs. There may be a plurality of pairs of magnetic flux concentrating limbs creating a respective plurality of magnetic flux concentrated regions.

[0015] The first element has at least two magnetic flux concentrating limbs. Therefore, the first element may have at least a first magnetic flux concentrating limb and a second magnetic flux concentrating limb. The second element may have at least a first magnetic flux concentrating limb and a second magnetic flux concentrating limb.

[0016] The first magnetic flux concentrating limb of the first element may correspond to the first magnetic flux concentrating limb of the second element. The second magnetic flux concentrating limb of the first element may correspond to the second magnetic flux concentrating limb of the second element. The magnetic flux concentrating limbs of each element may be positioned so as to have uniform spacing between said magnetic flux concentrating limbs.

[0017] It will be appreciated by those skilled in the art that to create a magnetic flux concentrated region, a minimum of two elements of the magnetic flux concentrator are used; wherein at least one magnetic flux concentrating limb of each element is aligned and spaced from a corresponding magnetic flux concentrating limb.

[0018] In a set of embodiments, the magnetic flux concentrator comprises a plurality of first elements and a plurality of second elements arranged so as to provide a plurality of respective magnetic flux concentrated regions. Each magnetic flux concentrated region may be created by a respective pair of magnetic flux concentrating limbs. There may be a plurality of pairs of first and second elements wherein said pairs are arranged in rows and / or columns.

[0019] Thus, sensing arrays can be assembled using multiple elements of the magnetic flux concentrator depending on the size of array needed or desired.

[0020] There may be further structures between the pairs of magnetic flux concentrating limbs. For example, each magnetic flux concentrated region may be divided into separate magnetic flux concentrated regions (e.g. by having further structures between corresponding magnetic flux concentrating limbs) to form a one-dimensional or two-dimensional array of magnetic flux concentrated regions. In a set of embodiments, the magnetic flux concentrator comprises one or more third elements. The third element may be a different shape to the first element and / or the second element. The or each third element may be configured (e.g. shaped) to be positioned between (e.g. the distal ends of) two corresponding magnetic flux concentrating limbs so as to divide the concentrated magnetic flux region into a plurality of concentrated magnetic flux regions. Each of the plurality of concentrated magnetic flux regions created by dividing the concentrated magnetic flux region may provide a region where a magnetic sensor can be placed for improved sensitivity of said sensor. This further allows an increased number of magnetic sensors to be provided in a given area without substantially sacrificing sensitivity and, in some cases, potentially improving sensitivity.

[0021] In a set of embodiments, each of the one or more third elements may be an intermediate element; wherein each intermediate element is arranged between, and spaced from, the corresponding magnetic flux concentrating limbs to divide the concentrated magnetic flux region into a plurality of concentrated magnetic flux regions.

[0022] The third element may comprise one or more magnetic flux concentrating limbs. The third (e.g. intermediate) element may resemble a portion of a magnetic flux concentrating limb (e.g. having the same width as the magnetic flux concentrating limbs). The third element may be a rectangular element (e.g. resembling an island) and may have the same width as the distal end of each magnetic flux concentrating limb. Including one or more intermediate (e.g. ‘island’) elements may provide improved spatial resolution in compact array applications. This may be especially useful for precision-required fields like neurology and advanced material analysis. Optionally, there may be a cascade of magnetic flux concentrating limbs and / or a cascade of magnetic flux concentrating elements. For example, between two corresponding magnetic flux concentrating limbs there may be two or more further elements and / or two or more further magnetic flux concentrating limbs. Each further magnetic flux concentrating limb may have a width smaller than the width of the magnetic flux concentrating limbs.

[0023] Each of the magnetic flux concentrating limbs may extend in mutually oblique, parallel, antiparallel or orthogonal directions. In a set of embodiments, the magnetic flux concentrating limbs extend in mutually parallel, anti-parallel or orthogonal directions.

[0024] Each of the first and second, and optionally third, elements may have a body portion. The magnetic flux concentrating limbs of an element may extend from the body portion of said element. The two or more magnetic flux concentrating limbs of an element may be monolithic with the body portion of said element (i.e. the magnetic flux concentrating limbs and body portion of the element form a single unit).

[0025] Each magnetic flux concentrating limb has a proximal end and a distal end. The proximal end of each magnetic flux concentrating limb of an element may be proximal to the body portion of said element. The distal end of each magnetic flux concentrating limb of an element may be distal to the body portion of said element.

[0026] The distal end of a magnetic flux concentrating limb of an element may be aligned with and spaced from the distal end of a corresponding magnetic concentrating limb (i.e. of a different element) so as to create a magnetic flux concentrated region proximal to, and between, the distal ends of said magnetic flux concentrating limbs.

[0027] The body portion may be an elongate body portion. The elongate body portion may extend along a first axis. The magnetic flux concentrating limbs may extend parallel to a second axis perpendicular to the first axis. The elongate body portion may extend between two ends. The magnetic flux concentrating limbs may extend from the elongate body portion at positions that are spaced from each end of the elongate body portion.

[0028] In a set of embodiments, the magnetic flux concentrating limbs and body portion of each element lie in the same plane. For a device comprising a plurality of magnetic sensors and / or magnetic sensor elements, the magnetic flux concentrator and the plurality of magnetic sensors and / or magnetic sensor elements may lie in the same plane.

[0029] The body portion of each element may have any suitable (e.g. polygonal) shape. The body portion may have a plurality of sides (e.g. four).

[0030] In a set of embodiments, the first element and second element each comprise: a (e.g. respective) body portion from which the magnetic flux concentrating limbs of the (e.g. respective) element extend; wherein said magnetic flux concentrating limbs extend from at least a first side of the (e.g. respective) body portion.

[0031] Each of the elements may have the two or more magnetic flux concentrating limbs extending from two or more sides of the body portion. For example, one or more magnetic flux concentrating limbs may extend from each side of the body portion. A plurality of the magnetic flux concentrating limbs may extend from one or more sides of the body portion of one or more of the elements of the magnetic flux concentrator. In some embodiments, a first plurality of magnetic flux concentrating limbs extend from a first side of each body portion of one or more (e.g. first, second, or third etc.) elements of the magnetic flux concentrator and a second plurality of magnetic flux concentrating limbs extend from a second side of said body portion, opposite to the first side.

[0032] In a set of embodiments, the magnetic flux concentrator comprises: a plurality of first elements each having a body portion and a plurality of magnetic flux concentrating limbs extending from a single side of said body portion; a plurality of second elements each having a body portion and a plurality of magnetic flux concentrating limbs extending from at least two opposing sides of said body portion of each second element.

[0033] The plurality of the first elements and plurality of second elements may be arranged such that each magnetic flux concentrating limb is aligned with, and spaced from, a corresponding magnetic flux concentrating limb to create a concentrated magnetic flux region.

[0034] Each second element may have at least twice the number of magnetic flux concentrating limbs as each first element. Each second element may have an equal number of magnetic flux concentrating limbs on opposite sides of its body portion.

[0035] Each of the magnetic concentrating limbs may have a shape suitable for concentrating magnetic flux at a concentrated magnetic flux region when aligned with and spaced from a corresponding magnetic concentrating limb.

[0036] Each of the magnetic concentrating limbs (e.g. of the first and / or second element) may have a similar shape. Each of the magnetic concentrating limbs (e.g. of the first and / or second element) may have the same shape.

[0037] Each of the magnetic concentrating limbs (e.g. of the first and / or second element) may have a length from their proximal end to their distal end and a width perpendicular to the length (e.g. across the limb).

[0038] Each of the magnetic concentrating limbs may have a uniform length. However, in a set of embodiments, two or more of the magnetic concentrating limbs of each magnetic flux concentrator element have different lengths. Thus, two or more adjacent concentrated magnetic flux regions may be mutually offset (i.e. not aligned along a common axis). In such examples, where the magnetic concentrating limbs of each magnetic flux concentrator element have different lengths, the summed length of each pair of corresponding magnetic flux concentrating limbs that create each concentrated magnetic flux region may be uniform (e.g. over the plurality of pairs of magnetic flux concentrating limbs).

[0039] Each of the magnetic concentrating limbs (e.g. of the first and / or second element) may have a constant width along their length. In some embodiments, however, each magnetic concentrating limb has a width that is smallest at its distal end. For example, each magnetic concentrating limb may have a width that decreases, from its proximal end to its distal end, i.e. along its length. The width of each magnetic concentrating limb may decrease linearly or according to a non-linear function. The elements of the magnetic flux concentrator may be arranged so that the magnetic concentrating limbs of said elements are mutually parallel.

[0040] In a set of embodiments, each of the first element and second element has a respective plurality of adjacent magnetic concentrating limbs and gaps therebetween (i.e. the gaps between the plurality of adjacent magnetic concentrating limbs) having a (e.g. maximum) size that is equal to or less than twice the width of each of the magnetic concentrating limbs. Each gap may have a (e.g. maximum) size that is equal to or less than the width of each of the magnetic concentrating limbs. Each gap may be defined by the (e.g. maximum) distance between inner edges of adjacent magnetic concentrating limbs. Adjacent magnetic concentrating limbs are to be understood as neighbouring magnetic concentrating limbs which extend from the same side of the body portion of the element.

[0041] The first element and the second element may have the same shape. Alternatively the first element and the second element may have a different shape. The first element and the second element may have different configurations of magnetic flux concentrating limbs, e.g. the first element may have a different number and / or arrangement of magnetic flux concentrating limbs compared to the second element.

[0042] The first element and second element are arranged such that each magnetic flux concentrating limb is aligned with, and spaced from, a corresponding magnetic flux concentrating limb to create a concentrated magnetic flux region. Each concentrated magnetic flux region may have a size defined by the distance between elements of the magnetic flux concentrator most proximal to said region (e.g. the smallest gap between elements of magnetic flux concentrator either side of the concentrated magnetic flux region). The plurality of concentrated magnetic flux regions may have a uniform size. Each concentrated magnetic flux region may be sized to fit a magnetic (e.g. TMR) sensor. For example, the smallest gap between elements of magnetic flux concentrator either side of the concentrated magnetic flux region may have a similar size to a TMR sensor or TMR sensor element (e.g. the size of the gap may be within 5%; optionally within 2%; of the size of the TMR sensor or TMR sensor element). Having a gap that is not much larger than the TMR sensor or TMR sensor element helps to prevent dissipation and / or stray of the magnetic field.

[0043] In a set of embodiments, the smallest spacing between elements of the magnetic flux concentrator (e.g. the size of each concentrated magnetic flux region) is less than 1 cm, e.g. less than 5 mm, e.g. less than 2 mm, e.g. less than 1 mm. The smallest spacing between elements of the magnetic flux concentrator is preferably large enough to allow a magnetic sensor or magnetic sensor element to be placed therein. The smallest spacing may be the spacing between a magnetic flux concentrating limb of the first element and a corresponding magnetic flux concentrating limb of the second element. Alternatively, the smallest spacing may be the spacing between a magnetic flux concentrating limb and a further (e.g. third) element of the magnetic flux concentrator.

[0044] Each first element of the magnetic flux concentrator may have a shape resembling a chain of contiguous T-shapes. Each second element of the magnetic flux concentrator may have a shape resembling a chain of contiguous cross-shapes. One or more (e.g. further) elements of the magnetic flux concentrator may have a shape resembling a cross-shape having four arms wherein each of the four arms is a magnetic flux concentrating limb. Magnetic flux concentrators embodying the invention provide two or more concentrated magnetic flux regions. Each of the concentrated magnetic flux regions may be associated with a corresponding magnetic sensor configured to output a signal on a respective measurement channel, when the magnetic sensor is exposed to a magnetic field. For example, a magnetic sensor may be located (e.g. centrally) in each of the concentrated magnetic flux regions and configured to output a signal on a respective measurement channel, when the magnetic sensor is exposed to a magnetic field.

[0045] As a plurality of measurement channels may be provided with magnetic flux concentration at each concentrated magnetic flux region, it is possible to sense weak magnetic fields at a plurality of locations (e.g. on a plane), the magnetic field at each location being provided by a respective measurement channel. This may allow a map of sensed magnetic fields to be generated by a processing module receiving respective measurement signals on each measurement channel. The invention may therefore help to provide a way of increasing the density of such measurement channels, this allowing for higher spatial resolution and improved sensitivity for magnetic mapping.

[0046] The magnetic flux concentrator may, therefore, be a multi-channel magnetic flux concentrator (e.g. for a multi-channel magnetic sensing device having a plurality of magnetic sensors). For example, the magnetic flux concentrator may, therefore, be an N-channel magnetic flux concentrator for an N-channel magnetic sensing device having N magnetic sensors. The ability to measure multiple magnetic fields may allow for more comprehensive monitoring and analysis in various applications, from medical diagnostics to industrial testing. The elements of the magnetic flux concentrator may be arranged to provide an array of concentrated magnetic flux regions. The array of concentrated magnetic flux regions may have M rows of magnetic flux regions and N columns of magnetic flux regions - i.e. the array may be an M X N array. Optionally, M > 1 and N > 1 .

[0047] At least one magnetic sensor element or magnetic sensor may be located at each magnetic flux region, thereby providing a magnetic sensor element array or magnetic sensor array, e.g. an M X N magnetic sensor array.

[0048] In a set of embodiments, the magnetic flux concentrator may provide a plurality of rows and / or columns of magnetic flux concentrated regions. Adjacent rows and / or columns of magnetic flux concentrated regions may allow magnetic sensors to be arranged in respectively perpendicular orientations.

[0049] Magnetic sensors may be sensitive in more than one dimension, e.g. in respectively perpendicular dimensions. For example, TMR sensors may be sensitive along their x-axis and along their y-axis.

[0050] Along a first row and / or column of concentrated magnetic flux regions, the magnetic flux concentrating limbs (e.g. either side of said row and / or column) may be parallel to a first axis (e.g. x-axis); and along a second row and / or column of concentrated magnetic flux regions, the magnetic flux concentrating limbs (e.g. either side of said row and / or column) may be parallel to a second axis (e.g. y-axis), perpendicular to the first axis. There may be a plurality of such first and second rows and / or columns. Thus, when exposed to a magnetic field (e.g. in use) magnetic flux may be concentrated along a first axis (e.g. x-axis) in a first row and / or column of concentrated magnetic flux regions and magnetic flux may be concentrated along a second axis (e.g. y-axis) in a second row and / or column of concentrated magnetic flux regions, perpendicular to the first axis. The second row and / or column may be adjacent to the first row and / or column.

[0051] This perpendicular arrangement of sensing directions may enhance spatial sensing capabilities.

[0052] One or more elements of the magnetic flux concentrator may have one or more lines of symmetry. In a set of embodiments, each element of the magnetic flux concentrator comprises at least one line of symmetry. In a set of embodiments, one or more of the elements of the magnetic flux concentrator has at least two lines of symmetry. The two lines of symmetry may be mutually perpendicular.

[0053] The magnetic flux concentrator may be disposed on a substrate. The substrate and the magnetic flux concentrator may be rigid or flexible. The substrate may be made from a low magnetic permeability material. The substrate may be a printed circuit board (PCB) or an integrated circuit die.

[0054] The magnetic flux concentrator may be provided on-chip in an integrated circuit die, integrated circuit package or integrated circuit device.

[0055] The invention may extend to a multi-channel magnetic sensor device comprising the magnetic flux concentrator according to the invention and a plurality of magnetic sensors; wherein each magnetic sensor is located in a respective concentrated magnetic flux region. Each magnetic sensor may be configured to output a measurement signal on a respective measurement channel. Each magnetic sensor may be positioned at the midpoint between two corresponding magnetic flux concentrating limbs.

[0056] Each magnetic sensor may be a tunnelling magnetoresistance (TMR) sensor, e.g. in a TMR array. Each TMR sensor may be placed within a respective concentrated magnetic flux region. TMR sensors are able to measure weak magnetic fields down to the pT scale and are small enough to be incorporated into a compact array to achieve high spatial resolution measurements. Using TMR sensors with the magnetic flux concentrator embodying the invention, thus allows for compact multi-channel sensor devices which can sense low-strength magnetic fields with improved magnetic gain.

[0057] Typically, the magnetic flux concentrator is made from a high magnetic permeability material - e.g. a high magnetic permeability alloy. The high magnetic permeability material (e.g. alloy) may comprise one or more of the list of metals comprising: iron, cobalt or nickel - e.g. nickel and iron.

[0058] According to a second aspect of the present invention there is provided a magnetic flux concentrator element, comprising: at least two magnetic flux concentrating limbs; wherein the magnetic flux concentrator element is arrangeable (e.g. arranged) with a corresponding element such that each magnetic flux concentrating limb is aligned with, and spaced from, a corresponding magnetic flux concentrating limb to create a concentrated magnetic flux region.

[0059] The invention extends to a magnetic sensor device, comprising the magnetic flux concentrator element of the second aspect and one or more magnetic sensors or magnetic sensor elements located at each concentrated magnetic flux region. The invention further extends to a method of operating such a magnetic sensor device; comprising exposing the magnetic sensor device to a magnetic field and sensing the magnetic field at each of the one or more magnetic sensors or magnetic sensor elements.

[0060] According to a third aspect of the present invention there is provided a magnetic flux concentrator, comprising: a first element having at least two magnetic flux concentrating limbs; and a second element having at least one magnetic flux concentrating limb; a third element having at least one magnetic flux concentrating limb; wherein: a first magnetic flux concentrating limb of the first element is aligned with, and spaced from, the magnetic flux concentrating limb of the second element to create a first concentrated magnetic flux region; and a second magnetic flux concentrating limb of the first element is aligned with, and spaced from, the magnetic flux concentrating limb of the third element to create a second concentrated magnetic flux region.

[0061] The invention extends to a magnetic sensor device, comprising the magnetic flux concentrator according to the third aspect and one or more magnetic sensors or magnetic sensor elements located at each concentrated magnetic flux region. The invention further extends to a method of operating such a magnetic sensor device; comprising exposing the magnetic sensor device to a magnetic field and sensing the magnetic field at each of the one or more magnetic sensors or magnetic sensor elements.

[0062] According to a fourth aspect of the present invention there is provided a magnetic flux concentrator, comprising: a first element having at least one magnetic flux concentrating limb; a second element having at least one magnetic flux concentrating limb; and an intermediate element; wherein: the first and second elements are arranged such that each magnetic flux concentrating limb is aligned with, and spaced from, a corresponding magnetic flux concentrating limb to create a concentrated magnetic flux region; and the intermediate element is arranged between, and spaced from, the corresponding magnetic flux concentrating limbs to divide the concentrated magnetic flux region into a plurality of concentrated magnetic flux regions.

[0063] The invention extends to a magnetic sensor device, comprising the magnetic flux concentrator of the fourth aspect and one or more magnetic sensors or magnetic sensor elements located at each concentrated magnetic flux region. The invention further extends to a method of operating such a magnetic sensor device; comprising exposing the magnetic sensor device to a magnetic field and sensing the magnetic field at each of the one or more magnetic sensors or magnetic sensor elements.

[0064] According to a fifth aspect of the present invention there is provided a magnetic flux concentrator, comprising: a plurality of elements each element having a plurality of magnetic flux concentrating limbs; wherein the plurality of elements are arranged such that each magnetic flux concentrating limb is aligned with, and spaced from, a corresponding magnetic flux concentrating limb to create a concentrated magnetic flux region.

[0065] The invention extends to a magnetic sensor device, comprising the magnetic flux concentrator of the fifth aspect and one or more magnetic sensors or magnetic sensor elements located at each concentrated magnetic flux region. The invention further extends to a method of operating such a magnetic sensor device; comprising exposing the magnetic sensor device to a magnetic field and sensing the magnetic field at each of the one or more magnetic sensors or magnetic sensor elements.

[0066] The elements of the magnetic flux concentrators described herein may be supplied separately. In one embodiment, however, the elements of the magnetic flux concentrator are supplied together as a kit. Thus when viewed from a sixth aspect the invention provides a kit for assembling a magnetic flux concentrator comprising a plurality of magnetic flux concentrator elements each magnetic flux concentrator element having a plurality of magnetic flux concentrating limbs; wherein the plurality of elements may be arranged such that each magnetic flux concentrating limb is aligned with, and spaced from, a corresponding magnetic flux concentrating limb to create a concentrated magnetic flux region.

[0067] The kit may comprise one or more (e.g. a plurality of) elements as described in relation to the first to fifth aspects. In a set of embodiments, the kit also comprises a plurality of (e.g. rectangular) intermediate magnetic flux concentrator elements. The magnetic flux concentrator elements of the kit are preferably made from the same material (e.g. a high magnetic permeability material).

[0068] The applicant appreciates that the magnetic flux concentrators described herein and the sensor devices in which they may be incorporated may be made more compact, which is particularly advantageous for wearable technology and portable devices. Thus, the first to fifth aspects of the invention may extend to a portable and / or wearable magnetic sensor device, comprising the magnetic flux concentrator of one of the first to fifth aspects and one or more magnetic sensors or magnetic sensor elements located at each concentrated magnetic flux region.

[0069] Embodiments of any aspect of the present invention may include one or more features of one or more of the other aspects of the present invention or its embodiments.

[0070] Brief description of the drawings

[0071] Embodiments of the invention will not be described, by way of example, with reference to the drawings, in which:

[0072] Fig. 1 schematically shows an apparatus including a magnetic flux concentrator embodying the present invention;

[0073] Fig. 2 schematically shows another version of the apparatus shown in Fig. 1 ;

[0074] Fig. 3 schematically shows two magnetic flux concentrators of the type shown in Fig. 1 combined to provide a modular magnetic flux concentrator; Fig. 4 schematically shows another magnetic flux concentrator embodying the present invention;

[0075] Fig. 5 schematically shows a compact version of the magnetic flux concentrator of Fig. 3;

[0076] Fig. 6 schematically shows a compact version of the magnetic flux concentrator of Fig. 4;

[0077] Fig. 7 schematically shows another magnetic flux concentrator embodying the present invention;

[0078] Fig. 8 schematically shows a compact version of the magnetic flux concentrator of Fig. 7;

[0079] Fig. 9 schematically shows a curved magnetic flux concentrator embodying the present invention;

[0080] Fig. 10 schematically shows another version of the magnetic flux concentrator of Fig. 9;

[0081] Fig. 11 schematically shows another version of the magnetic sensor device of Fig. 2;

[0082] Fig. 12 schematically shows another apparatus including a magnetic flux concentrator, similar to the type shown in Figs. 4 and 6, embodying the present invention;

[0083] Fig. 13 schematically shows part of a magnetic sensor device including a magnetic flux concentrator according to another embodiment of the invention;

[0084] Fig. 14 schematically shows another version of the apparatus shown in Fig. 1 wherein the magnetic flux concentrator has varied limb lengths;

[0085] Fig. 15 shows results from a simulation test of magnetic gain achieved by a traditional block magnetic flux concentrator;

[0086] Figs. 16 to 24 show results from simulation tests of magnetic gain achieved by magnetic flux concentrators embodying the present invention; and Figs. 25A-26C demonstrate simulation results and corresponding experimental results from testing magnetic flux concentrators embodying the invention.

[0087] Description of preferred embodiments

[0088] A TMR sensor is a type of magnetic sensor which makes use of arrays of magnetic tunnel junctions (MTJs) and is particularly suitable for sensing weak magnetic fields. The applicant has found that the performance of these sensors, and other magnetic sensors, can be improved by amplifying the magnetic field to be sensed at the location of each sensor or sensor element while also improving spatial resolution and device size when using the magnetic flux concentrators described herein.

[0089] Fig. 1 shows an apparatus embodying the invention. A magnetic flux concentrator is provided in combination with two magnetic sensors 7, in this example tunnel magnetoresistive (TMR) sensors 7, as part of a magnetic sensor device. The TMR sensors 7 each provide a respective measurement channel, making this device a ‘multi-channel’ magnetic sensor device.

[0090] The TMR sensors 7 are provided on a substrate (not shown). The magnetic flux concentrator 1 , includes a first element 4a having two magnetic flux concentrating limbs 2a; and a second element 4b having two magnetic flux concentrating limbs 2b. The size (S1 ) of the gap between limbs 2a, 2b is constant along the length of the limbs 2a, 2b.

[0091] The first and second elements 4a, 4b are arranged such that each magnetic flux concentrating limb 2a is aligned with, and spaced from, a corresponding magnetic flux concentrating limb 2b to create a concentrated magnetic flux region. The size (G) of the concentrated magnetic flux region is defined by the distance between the aligned pairs of magnetic flux concentrating limbs 2a, 2b. The magnetic flux concentrator advantageously concentrates magnetic flux on the magnetic sensors 7 to provide the most magnetic gain where the magnetic field is being sensed. This improves the sensitivity of the multi-channel magnetic sensor and allows very weak magnetic fields to be detected.

[0092] In Fig. 1 it can be seen that each element 4a, 4b of the magnetic flux concentrator has an elongate body portion 3a, 3b from which the magnetic flux concentrating limbs 2a, 2b extend. In this example, the magnetic flux concentrating limbs 2a, 2b extend from only one side of each elongate body portion 3a, 3b. Two magnetic flux concentrating limbs 2a, 2b extend from one of the long edges of each magnetic flux element.

[0093] Similarly to Fig. 1 , Fig. 2 shows an apparatus embodying the invention. In this apparatus, a magnetic flux concentrator is provided in combination with five magnetic sensors, e.g. tunnel magnetoresistive (TMR) sensors 7, as part of a ‘multi-channel’ magnetic sensor device. The TMR sensors 7 again are provided on a substrate (not shown). The magnetic flux concentrator of Fig. 2 includes a first element 4a’ having five magnetic flux concentrating limbs 2a’; and a second element 4b’ having five magnetic flux concentrating limbs 2b’.

[0094] The first and second elements 4a’, 4b’ are arranged such that each magnetic flux concentrating limb 2a’ is aligned with, and spaced from, a corresponding magnetic flux concentrating limb 2b’ to create a concentrated magnetic flux region. As with Fig. 1 , the magnetic flux concentrator advantageously concentrates magnetic flux on each of the five magnetic sensors 7 to provide the most magnetic gain where the magnetic field is being sensed. While Figs. 1 and 2 illustrate the scalability of the magnetic flux concentrators embodying the present invention; Figs. 3 to 14 illustrate the modularity and design flexibility which can be achieved using the invention.

[0095] Fig. 3 shows two magnetic flux concentrators 1 of the type shown in Fig. 1 arranged together to provide a modular magnetic flux concentrator for a 2x2 magnetic sensor array. The magnetic flux concentrator of Fig. 3 provides four concentrated magnetic flux regions 5, each of which could comprise a respective magnetic sensor or sensor element to provide said magnetic sensor with increased magnetic gain. This arrangement saves space and thus helps to reduce the footprint of the sensor array.

[0096] Fig. 4 shows a magnetic flux concentrator which also can be used to provide magnetic flux concentration for a 2x2 magnetic sensor array. The magnetic flux concentrator of Fig. 4 has a further element 8 in addition to the first element 4a and second element 4b. The first and second elements 4a, 4b have the same shape and the further element 8 has a different shape. The further element 8 has an elongate body portion 10 with four magnetic flux concentrating limbs 6a, 6b extending from the body portion 10, perpendicular to the length of the body portion and spaced from either end. On a first side of the body portion 10, i.e. on one of the long edges, two magnetic flux concentrating limbs 6a extend perpendicular to the length of the body portion 10. On a second side of the body portion 10, i.e. on the opposite long edge, the other two magnetic flux concentrating limbs 6b extend perpendicular to the length of the body portion 10. Each of the magnetic flux concentrating limbs 6a, 6b of the further element 8 is aligned with and spaced from a corresponding limb 2a, 2b of the first or second element 4a, 4b to create a concentrated magnetic flux region 5. This arrangement further reduces the footprint of the magnetic sensor array without sacrificing magnetic gain.

[0097] The Applicant has found that, reducing the spacing between the magnetic flux concentrating limbs allows for the magnetic flux concentrator to be even more compact, while surprisingly not significantly sacrificing magnetic gain. Fig. 5 schematically shows a magnetic flux concentrator similar to the type shown in Fig. 3. The spacing between the limbs on a single side of each element is reduced from S1 to S2 where S2 < S1 .

[0098] S1 may be between 1 and 2 times the width of each magnetic flux concentrating limb, wherein S2 may be less than the width of each magnetic flux concentrating limb.

[0099] Figs. 7 and 8 each show a magnetic flux concentrator embodying the invention having a first element 4a, 4a” with two magnetic flux concentrating limbs 2a, 2a”; a second element 4b, 4b” with two magnetic flux concentrating limbs 2b, 2b” and two intermediate elements 12. The first elements 4a and second elements 4a” are arranged such that each magnetic flux concentrating limb is aligned with, and spaced from, a corresponding magnetic flux concentrating limb to create a concentrated magnetic flux region 5; and each intermediate element 12 is arranged between, and spaced from, corresponding magnetic flux concentrating limbs 2a, 2b; 2a”, 2b” to divide the concentrated magnetic flux region into a plurality of concentrated magnetic flux regions 5.

[0100] Fig. 7 and Fig. 8 are the same except for the spacing between adjacent magnetic flux concentrating limbs. In Fig. 7 the size of the spacing between adjacent magnetic flux concentrating limbs is S1 and the size of the spacing between adjacent magnetic flux concentrating limbs in Fig. 8 is S2. The intermediate elements 12 are rectangular elements each having the same width as the magnetic flux concentrating limbs 2a, 2b. The intermediate element 12 may be composed of the same material as the first and second elements 4a, 4b; 4a”, 4b”.

[0101] Although, in this example, only one intermediate element 12 is shown between corresponding magnetic flux concentrating limbs; there may be a plurality of intermediate elements 12 between (e.g. and aligned with) corresponding magnetic flux concentrating limbs 2a, 2b to divide the concentrated magnetic flux region into a greater number of concentrated magnetic flux regions.

[0102] As can be seen in Fig. 7 and 8, the number of concentrated magnetic flux regions 5 increases from two to four with the addition of an intermediate element between corresponding magnetic flux concentrating limbs 2a, 2b; 2a”, 2b”.

[0103] Fig. 9 and Fig. 10 each show a magnetic flux concentrator embodying the present invention including a plurality of elements each element having four curved magnetic flux concentrating limbs 22a, 22b, 22c, 22d extending in orthogonal directions. Each element 14, 15, 16, 17 has a solid curved cross shape with uniform thickness.

[0104] The magnetic flux concentrator of Fig. 9 has a first element 14 having four magnetic flux concentrating limbs 22b, a second element 15 having four magnetic flux concentrating limbs 22a; a third element 16 having four magnetic flux concentrating limb 22c; and a fourth element 17 having four magnetic flux concentrating limb 22c. As can be seen in Fig. 9, a first magnetic flux concentrating limb 22b of the first element 14 is aligned with, and spaced from, a first magnetic flux concentrating limb 22a of the second element 15 to create a first concentrated magnetic flux region 5.

[0105] A second magnetic flux concentrating limb 22b of the first element 14 is aligned with, and spaced from, a first magnetic flux concentrating limb 22c of the third element 16 to create a second concentrated magnetic flux region 5.

[0106] A first magnetic flux concentrating limb 22d of the fourth element 17 is aligned with, and spaced from, a second magnetic flux concentrating limb 22a of the second element 15 to create a third concentrated magnetic flux region 5. A second magnetic flux concentrating limb 22d of the fourth element 17 is aligned with, and spaced from, a second magnetic flux concentrating limb 22c of the third element 16 to create a third concentrated magnetic flux region 5.

[0107] Fig.10 shows a further version of a magnetic flux concentrator embodying the invention, comprising the same features of Fig. 9 and including an intermediate element between corresponding magnetic flux concentrating limbs. Similar to the arrangements shown in Figs. 7 and 8, each concentrated magnetic flux region of Fig. 9 may be divided into a plurality of (e.g. two) concentrated magnetic flux regions by including an intermediate element 12’ between corresponding magnetic flux concentrating limbs and increasing the distance between the four elements 14-17 accordingly.

[0108] Fig. 11 shows a magnetic flux concentrator provided in combination with ten magnetic sensors, e.g. tunnel magnetoresistive (TMR) sensors 7, as part of a ‘multi-channel’ magnetic sensor device. The TMR sensors 7 again are provided on a substrate (not shown). Similarly to the magnetic flux concentrator of Fig. 2, the magnetic flux concentrator of Fig. 11 , includes a first element 4a’ having five magnetic flux concentrating limbs 2a’; and a second element 4b’ having five magnetic flux concentrating limbs 2b’. Fig. 11 shows that the number of concentrated magnetic flux regions is doubled by introducing an intermediate element between and aligned with corresponding limbs of the first and second elements. Thus, an array of ten magnetic sensors can be provided in a compact space while achieving increased magnetic gain.

[0109] The first and second elements 4a’, 4b’ are arranged such that each magnetic flux concentrating limb 2a’ is aligned with, and spaced from, a corresponding magnetic flux concentrating limb 2b’ to create a concentrated magnetic flux region which is divided into two concentrated magnetic flux regions by the intermediate element. As with Figs. 7 to 10, the intermediate element can be used to concentrate magnetic flux on each of the ten magnetic sensors 7 to provide magnetic gain where the magnetic field is being sensed.

[0110] Fig. 12 shows a magnetic flux concentrator provided in combination with nine magnetic sensors, e.g. tunnel magnetoresistive (TMR) sensors 7, as part of a ‘multi-channel’ magnetic sensor device based on a 3x3 magnetic sensor array. The magnetic flux concentrator has an uppermost element 4a’” and a lowermost element 4b’” with two further elements 8” therebetween. Each further element 8” of Fig. 12 is similar to the further element of Figs. 4 and 6. Each further element 8” of Fig. 12 has an elongate body portion 10 with six magnetic flux concentrating limbs 6a”, 6b” extending from the body portion 10”. On a first side of the body portion 10, i.e. on one of the long edges, two magnetic flux concentrating limbs 6a extend perpendicular to the length of the body portion 10. On a second side of the body portion 10, i.e. on the opposite long edge, the other two magnetic flux concentrating limbs 6b extend perpendicular to the length of the body portion 10. Each of the magnetic flux concentrating limbs 6a, 6b of the further element 8 is aligned with and spaced from a corresponding limb 2a, 2b of the first or second element 4a, 4b to create a concentrated magnetic flux region 5. This arrangement further reduces the footprint of the magnetic sensor array without sacrificing magnetic gain.

[0111] The Applicant has found that, reducing the spacing between the magnetic flux concentrating limbs allows for the magnetic flux concentrator to be even more compact, while surprisingly not significantly sacrificing magnetic gain. Fig. 5 schematically shows a magnetic flux concentrator similar to the type shown in Fig. 3. The spacing between the limbs on a single side of each element is reduced from S1 to S2 where S2 < S1 .

[0112] S1 may be between 1 and 2 times the width of each magnetic flux concentrating limb, wherein S2 may be less than the width of each magnetic flux concentrating limb.

[0113] Fig. 13 shows the ‘curved cross’ magnetic flux concentrator of the type shown in Fig. 9 in a two-dimensional magnetic sensing array of TMR sensors 7, 7’. Having four magnetic concentrating limbs extending from the centre of each element (e.g. 14, 15, 16, 17) in mutually orthogonal directions allows for neighbouring rows and columns of the TMR sensors 7, 7’ to be perpendicular to eachother. Each row and each column of TMR sensors is either oriented along the x-axis or the y-axis. For example, the first row of TMR sensors 7’ senses along the x-axis and the second row of TMR sensors 7 senses along the y-axis. Having the TMR sensors 7,7’ arranged along perpendicular axes (i.e. x and y) further enhances spatial sensing capabilities. Fig. 14 schematically shows a variant of the apparatus shown in Fig. 1 in which there is a magnetic flux concentrator formed from two magnetic flux concentrator elements 40a, 40b each having two magnetic flux concentrating limbs 20a, 20a’ and 20b, 20b’ of different lengths Li and L2. As shown in Fig. 14, the magnetic flux concentrator elements 40a, 40b can be arranged so as to create concentrated magnetic flux regions between aligned corresponding limbs 20a, 20b and 20a’, 20b’. In other examples, there may be further pairs of such magnetic flux concentrating limbs having different lengths. The Applicant has found that having offset concentrated magnetic flux regions may be useful for certain applications which require offset sensing positions. Discrepancies in the magnetic gain achieved at each concentrated magnetic flux region, caused by the offset, may be compensated for using software.

[0114] Devices incorporating such magnetic flux concentrators according to the invention may be portable and / or wearable.

[0115] Each of the magnetic flux concentrators described herein may be used to improve the operation of a magnetic sensor device incorporating said magnetic flux concentrator. In operation, a magnetic sensor device will be exposed to a magnetic field which is sensed at each of the one or more magnetic sensors or magnetic sensor elements. Where there are a plurality of magnetic sensors each magnetic sensor may provide a measurement signal on a respective measurement channel indicative of the magnetic field sensed at said sensor. A processing system (not shown) may comprise circuitry for processing the measurement signals in the appropriate manner according to the specific application for the particular magnetic sensor device. The Applicant has carried out some simulation studies and real-world experiments of a selection of the embodiments seen in Figs. 1-14.

[0116] The performance of some of the magnetic flux concentrators is demonstrated by graphs of simulated gain factors. The gain achieved by the simulated magnetic flux concentrators was determined by the Applicant by calculating ratios of flux densities. First, in the simulation area a unidirectional magnetic flux density, Bo, is established by defining the magnetic scalar potential, with the field direction aligned to the magnetic flux concentrating limbs. A measurement line, e.g. aligned parallel with the magnetic field, is placed centrally within a concentrated magnetic flux region in the gap between corresponding magnetic flux concentrator elements. The presence of the magnetic flux concentrator alters the magnetic flux density in this region, and the flux density along the measurement line is recorded and averaged during the simulation, yielding a value Bi for the gap. The gain is then calculated by dividing the averaged flux density Bi along the measurement line by the defined value Bo.

[0117] Fig. 14 shows a graph of magnetic gain factor for a traditional block magnetic flux concentrator. The block magnetic flux concentrator has two identical rectangular elements separated by a gap between which a single magnetic sensor may be placed. The graph shows how the gain factor changes as a function of the position along the gap between the two elements of the magnetic flux concentrator along lines A and B.

[0118] The simulated magnetic gain across a gap of the same size is shown in Fig. 15 for a magnetic flux concentrator shown in Fig. 1. The graph shows that using a magnetic flux concentrator according to the invention increases the magnetic flux concentration across the gap between elements 4a, 4b along the lines a and b which are each centrally aligned with a respective pair of magnetic flux concentrating limbs.

[0119] Fig. 16 shows how the magnetic flux concentrator of Fig. 2 affects the surrounding magnetic field. It can be seen that the maximum magnetic flux density is observed between each pair of corresponding magnetic flux concentrating limbs which align to provide concentrated magnetic flux regions.

[0120] Fig. 17 is a graph of the gain factor across one of the gaps of the magnetic flux concentrator of Fig. 2. A gain factor of above 6 is shown by the graph at the midpoint between corresponding magnetic flux concentrating limbs.

[0121] Figs. 19A, 19B and 20 show simulation results of the magnetic flux concentrator of the type shown in Fig. 12, scaled to a 3x5 array. Fig. 19A is a simulation showing how field lines are guided which demonstrates the magnetic field concentration achieved using said magnetic flux concentrator.

[0122] Fig. 19B shows the same 3x5 array in diagrammatic form showing an upper, middle and lower row of concentrated magnetic flux regions and five columns of concentrated magnetic flux regions labelled: P1 ,P2, P3, P4 and P5.

[0123] Even when the magnetic flux concentrator is used in these larger arrays, it can be seen that surprisingly high gain factors are observed.

[0124] Fig. 20 shows that the upper and lower rows demonstrate a gain factor of approximately 17 and the middle row demonstrates a gain factor of approximately 21 , both much higher than the gain factor achieved using a traditional block magnetic flux concentrator.

[0125] Fig. 21 shows the magnetic flux concentration simulated for the magnetic flux concentrator shown in Fig. 11 . As shown in Fig. 11 , each concentrated magnetic flux region is divided into two magnetic flux regions by the intermediate elements between each pair of corresponding magnetic flux concentrating limbs.

[0126] Fig. 22 shows a graph of simulated gain factor over the distance between corresponding magnetic flux concentrating limbs. The graph shows that a high magnetic gain of above 6 is achieved for the two concentrated magnetic flux regions and that the magnetic flux concentration is substantially the same (i.e. shown by the symmetrical curves of gain factor).

[0127] Figs. 23 and 24 show simulation results of a magnetic flux concentrator having a first element 4a’ having three magnetic flux concentrating limbs 2a’, a second element 4b’ having three magnetic flux concentrating limbs 2b’ and two intermediate elements 12” disposed between and aligned with two corresponding magnetic flux concentrating limbs 2a’, 2b’. As shown in Fig. 23, there are three concentrated magnetic flux regions 5 between each pair of corresponding limbs 2a’, 2b’. Fig. 23 shows the magnetic flux concentration observed in the simulation for this arrangement.

[0128] Fig. 24 shows a graph of simulated gain factor over the distance between corresponding magnetic flux concentrating limbs 2a’, 2b’ of the magnetic flux concentrator of Fig. 23. Similar gain factors of approximately 5 are observed for the outermost concentrated magnetic flux regions, with a slightly reduced gain factor of approximately 4 for the central concentrated magnetic flux region.

[0129] Simulations were conducted using COMSOL Multiphysics to model two versions of magnetic flux concentrators embodying the present invention.

[0130] The first version is a 1x3 magnetic flux concentrator having a first magnetic flux concentrator element 4a” and a second magnetic flux concentrator element 4b” each element 4a”, 4b” having three magnetic flux concentrating limbs 2a”, 2b” which correspond to form three concentrated magnetic flux regions, as shown in Fig. 25A.

[0131] The second version is a 2x3 magnetic flux concentrator having a first magnetic flux concentrator element 4a”” having three magnetic flux concentrating limbs 2a”” and a second magnetic flux concentrator element 4b”” having three magnetic flux concentrating limbs 2b””, with an intermediate element 12” between each corresponding pair of magnetic flux concentrating limbs 2a””, 2b””, to form six concentrated magnetic flux regions, as shown in Fig. 26A.

[0132] The simulation results indicate that the magnetic field is effectively concentrated in the concentrated magnetic flux regions between corresponding limbs of the magnetic flux concentrator. The gain factor derived from the simulation of Fig. 25A was 4.3, and the gain factor derived from the simulation of Fig. 26A was 3.2.

[0133] The respective performance of each of the magnetic flux concentrators of Fig. 25A and 26A was also tested in the laboratory by the applicant by measuring gains of multi-channel magnetic sensing devices with magnetic flux concentrators according to the designs on a common PCB substrate. The baseline sensitivities of TMR sensors were tested before testing the impact of the magnetic flux concentrators on the sensitivities of said TMR sensors. After integrating TMR sensors with the magnetic flux concentrators, the TMR sensitivities were measured again to determine the gain provided by each of the configurations of Fig. 25A and 26A. The gains were also compared to those obtained from a single channel TMR sensor with a simple T-shaped magnetic flux concentrator, which provided a gain factor of 2.91 .

[0134] To test the design of Fig. 25A a device, as shown in Fig. 25B, was made comprising a 1x3 magnetic flux concentrator for a three-channel TMR sensor array, i.e. having three measurement channels. The same dimensions and materials were used in the laboratory experiment as were specified in the simulation. The results of magnetic gain measurements at each channel (i.e. each TMR sensor) are shown in Fig. 25C - i.e. 3.7469, 3.6209 and 3.5121 going from left to right.

[0135] Similarly to test the design of Fig. 26A a device was made, as shown in Fig. 26B, comprising a 2x3 magnetic flux concentrator for a six-channel TMR sensor array, i.e. having six measurement channels. The same dimensions and materials were used in the laboratory experiment as were specified in the simulation. The results of magnetic gain measurements at each channel (i.e. each TMR sensor) are shown in Fig. 26C - i.e. for the top row: 3.2423, 3.2370, and 3.228 going from left to right; and for the bottom row 3.2188, 3.1457 and 3.2517 going from left to right.

[0136] Both the simulation and experimental results show demonstrably improved gain factors. Therefore, the applicant has found that the magnetic flux concentrator configurations disclosed herein for multi-channel magnetic sensing can synergistically enhance the sensitivity of magnetic sensors, e.g. TMR sensors, and reduce the footprint of such multi-channel magnetic sensors. In particular, these configurations achieve sensitivity gains that are comparable to or surpass those of traditional single-channel magnetic flux concentrator configurations.

[0137] Traditional magnetic flux concentrator designs are predominantly tailored for single-channel measurements, inherently incorporating air gaps between each sensor and magnetic flux concentrator to isolate magnetic channels. This conventional structure, while functional for individual measurements, imposes limitations on the compactness of the device and can detrimentally affect sensitivity due to the spatial separation of the sensors.

[0138] The magnetic flux concentrators according to the present invention may thus provide more compact multi-channel magnetic sensing devices, as the space typically reserved for air gaps in single-channel magnetic flux is eliminated. Surprisingly, having multiple magnetic flux concentrating limbs in a single element does not compromise, but rather enhances, the sensitivity of each measurement channel.

Claims

Claims1 . A magnetic flux concentrator, comprising: a first element having at least two magnetic flux concentrating limbs; and a second element having at least two magnetic flux concentrating limbs, wherein the first and second elements are arranged such that each magnetic flux concentrating limb is aligned with, and spaced from, a corresponding magnetic flux concentrating limb to create a concentrated magnetic flux region.

2. The magnetic flux concentrator of claim 1 , wherein the magnetic flux concentrator comprises a plurality of first elements and a plurality of second elements arranged so as to provide a plurality of magnetic flux concentrated regions.

3. The magnetic flux concentrator of claim 1 or 2, comprising one or more third elements having a different shape to the first element and the second element.

4. The magnetic flux concentrator of claim 3, wherein the, or each, third element is configured to be positioned between two corresponding magnetic flux concentrating limbs so as to divide the concentrated magnetic flux region into a plurality of concentrated magnetic flux regions.

5. The magnetic flux concentrator of any preceding claim, wherein the magnetic flux concentrating limbs extend in mutually parallel, anti-parallel or orthogonal directions.

6. The magnetic flux concentrator of any preceding claim, wherein each the first and second elements has a body portion; and the magnetic flux concentrating limbs of each element extend from the body portion of said element.

7. The magnetic flux concentrator of claim 6, wherein the magnetic flux concentrating limbs of an element are monolithic with the body portion of said element.

8. The magnetic flux concentrator of claim 6 or 7, wherein the body portion is an elongate body portion.

9. The magnetic flux concentrator of claim 8, wherein the elongate body portion extends along a first axis and the magnetic flux concentrating limbs extend parallel to a second axis perpendicular to the first axis.

10. The magnetic flux concentrator of claim 8 or 9, wherein the elongate body portion of each element extends between two ends and the magnetic flux concentrating limbs of each element are positioned along the elongate body portion so that they are spaced from each end of the elongate body portion11 . The magnetic flux concentrator of any preceding claim, wherein a plurality of magnetic flux concentrating limbs extend from one or more sides of the body portion of one or more of the elements of the magnetic flux concentrator.

12. The magnetic flux concentrator of any of claims 6 to 11 , comprising a first plurality of magnetic flux concentrating limbs extending from a first side of each body portion of one or more elements of the magnetic fluxconcentrator and a second plurality of magnetic flux concentrating limbs extending from a second side of said body portion, opposite to the first side.

13. The magnetic flux concentrator of any preceding claim, comprising: a plurality of first elements each having a body portion and a plurality of magnetic flux concentrating limbs extending from a single side of said body portion; a plurality of second elements each having a body portion and a plurality of magnetic flux concentrating limbs extending from at least two opposing sides of said body portion of each second element.

14. The magnetic flux concentrator of any preceding claim, wherein: each of the first element and second element has a respective plurality of adjacent magnetic concentrating limbs and gaps therebetween having a maximum size that is equal to or less than twice the width of each of the magnetic concentrating limbs.

15. The magnetic flux concentrator of claim 14, wherein each gap has a maximum size that is equal to or less than the width of each of the magnetic concentrating limbs.

16. The magnetic flux concentrator of any preceding claim, wherein each concentrated magnetic flux region has a size defined by the distance between elements of the magnetic flux concentrator most proximal to said region.

17. The magnetic flux concentrator of any preceding claim, wherein each of the concentrated magnetic flux regions is associated with a corresponding magnetic sensor configured to output a signal on arespective measurement channel, when the magnetic sensor is exposed to a magnetic field.

18. The magnetic flux concentrator of any preceding claim, wherein the magnetic flux concentrator provides a plurality of rows and columns of magnetic flux concentrated regions.

19. The magnetic flux concentrator of claim 18, wherein along a first row or column of concentrated magnetic flux regions, the magnetic flux concentrating limbs are parallel to a first axis and along a second row or column of concentrated magnetic flux regions, the magnetic flux concentrating limbs are parallel to a second axis, perpendicular to the first axis.

20. A magnetic flux concentrator element, comprising: at least two magnetic flux concentrating limbs; wherein the magnetic flux concentrator element is arrangeable with a corresponding element such that each magnetic flux concentrating limb is aligned with, and spaced from, a corresponding magnetic flux concentrating limb to create a concentrated magnetic flux region.21 . A magnetic flux concentrator, comprising: a first element having at least two magnetic flux concentrating limbs; and a second element having at least one magnetic flux concentrating limb; a third element having at least one magnetic flux concentrating limb; wherein:a first magnetic flux concentrating limb of the first element is aligned with, and spaced from, the magnetic flux concentrating limb of the second element to create a first concentrated magnetic flux region; and a second magnetic flux concentrating limb of the first element is aligned with, and spaced from, the magnetic flux concentrating limb of the third element to create a second concentrated magnetic flux region.

22. A magnetic flux concentrator, comprising: a first element having at least one magnetic flux concentrating limb; a second element having at least one magnetic flux concentrating limb; and an intermediate element; wherein: the first and second elements are arranged such that each magnetic flux concentrating limb is aligned with, and spaced from, a corresponding magnetic flux concentrating limb to create a concentrated magnetic flux region; and the intermediate element is arranged between, and spaced from, the corresponding magnetic flux concentrating limbs to divide the concentrated magnetic flux region into a plurality of concentrated magnetic flux regions.

23. A magnetic flux concentrator, comprising: a plurality of elements each element having a plurality of magnetic flux concentrating limbs; wherein the plurality of elements are arranged such that each magnetic flux concentrating limb is aligned with, and spaced from, a corresponding magnetic flux concentrating limb to create a concentrated magnetic flux region.

24. A magnetic sensor device, comprising the magnetic flux concentrator according to any preceding claim and one or more magnetic sensors or magnetic sensor elements located at each concentrated magnetic flux region.

25. The magnetic sensor device of claim 24, wherein the device is a multi-channel magnetic sensor device comprising a plurality of magnetic sensors; wherein each magnetic sensor is located in a respective concentrated magnetic flux region and is configured to output a measurement signal on a respective measurement channel.

26. The magnetic sensor device of claim 24 or 25, wherein each magnetic sensor is a tunnelling magnetoresistance, TMR, sensor.

27. A kit for assembling a magnetic flux concentrator comprising a plurality of magnetic flux concentrator elements, each magnetic flux concentrator element having a plurality of magnetic flux concentrating limbs; wherein the plurality of elements may be arranged such that each magnetic flux concentrating limb is aligned with, and spaced from, a corresponding magnetic flux concentrating limb to create a concentrated magnetic flux region.

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