GB2635168A

GB2635168A - Transducer array for guided wave testing

Info

Publication number: GB2635168A
Application number: GB2316680.4A
Authority: GB
Inventors: Sanderson Allan; Sanderson Ruth
Original assignee: Full Matrix Ltd
Current assignee: Full Matrix Ltd
Priority date: 2023-10-31
Filing date: 2023-10-31
Publication date: 2025-05-07
Also published as: GB202316680D0

Abstract

The transducer array 250 comprises a first transducer 100 and a second transducer 200. The first transducer comprises a first magnet 110 and a first coil 120 wound around the first magnet. The second transducer comprises a second magnet 210 and a second coil 220 wound around the second magnet. The first magnet and the second magnet have substantially opposite magnetic field orientations, and the first coil and the second coil have substantially opposite current flow directions.

Description

TITLE

Transducer array for guided wave testing

TECHNOLOGICAL FIELD

Examples of the disclosure relate to transducers. Some relate to a transducer array for guided wave testing. For example for guided wave testing of pipes such as oil pipelines.

BACKGROUND

Guided wave testing (GWT) is an evaluation method used to inspect elongate structures. It employs acoustic waves which propagate along an elongate structure while guided by its boundaries, allowing the waves to travel a long distance with little loss in energy. Guided wave testing is non-destructive and can be used for inspecting pipelines, rail tracks, rods and other elongate structures.

Transducers convert a signal in one form of energy to a signal in another. Transducers may be used for various forms of testing. In guided wave testing, transducers are used to convert electrical signals into vibrations in the elongate structure, and to subsequently convert vibrations in the elongated structure into electrical signals.

The transducers may form a transducer array mounted around the perimeter of the elongated structure, for example around the circumference of a pipe. This allows the generation of waves, such as axially symmetric waves that propagates along the elongated structure in both the forward and backward directions. In some examples, the transducer array operates in a pulse-echo configuration, where the same transducer array both propagates and detects the waves. In other examples, one transducer array propagates the waves and another transducer subsequently detects the waves. Based on the detected waves, defects in the elongated structure can be determined.

BRIEF SUMMARY

According to various, but not necessarily all, examples there is provided a transducer array for guided wave testing of an elongate member. The transducer array comprises: a first transducer and a second transducer. The first transducer comprises: a first magnet; and a first coil wound around the first magnet. The second transducer comprises: a second magnet; and a second coil wound around the second magnet. The first magnet and the second magnet have substantially opposite magnetic field orientations, and the first coil and the second coil have substantially opposite current flow directions.

The transducer array may be configured to couple to the elongate member for guided wave testing of the elongate member. The transducer array may comprise a plurality of transducers comprising the first transducer and the second transducer. The transducer array may be configured such that when the transducer array is coupled to the elongate member, the plurality of transducers are positioned around the perimeter of the elongate member. The plurality of transducers may have alternating magnetic field orientations, and alternating current flow directions.

The first coil may be wound around the first magnet with an axis of winding substantially perpendicular to a magnetic axis of the first magnet from the north magnetic pole to the south magnetic pole, and the second coil may be wound around the second magnet with an axis of winding substantially perpendicular to a magnetic axis of the first magnet from the north magnetic pole to the south magnetic pole.

The first coil may be wound around the first magnet substantially parallel to a plane at least partially defined by a magnetic axis from the north magnetic pole to the south magnetic pole of the first magnet, and the second coil may be wound around the second magnet substantially parallel to a plane at least partially defined by a magnetic axis from the north magnetic pole to the south magnetic pole of the second magnet.

The first magnet may have a length, a height and a width, wherein the height is parallel to the magnetic axis from the north to south magnetic pole. The first coil may be wound around the length and height of the first magnet. The second magnet may have a length, a height and a width, wherein the height is parallel to the magnetic axis from the north to south magnetic pole. The second coil may be wound around the length and height of the second magnet. The length of the first magnet may be twice or more the size of the width of the first magnet. The length of the second magnet may be twice or more the size of the width of the second magnet.

A magnetic axis for the first magnet, defined from the north magnetic pole to the south magnetic pole, may be substantially opposite to a magnetic axis for the second magnet, defined from the north magnetic pole to the south magnetic pole. The north magnetic pole of the first magnet may be closer to the south magnetic pole of the second magnet than it is to the north magnetic pole of the second magnet.

The transducer array may be configured such that when the transducer array is coupled to the elongate member, a magnetic axis for the first magnet, defined from the north magnetic pole to the south magnetic pole, is substantially perpendicular to a surface of the elongate member, and a magnetic axis for the second magnet, defined from the north magnetic pole to the south magnetic pole, is substantially perpendicular to a surface of the elongate member.

The transducer array may be configured such that when the transducer array is coupled to the elongate member, for the first magnet the south pole is closer to the elongate member than the north pole is to the elongate member, and for the second magnet the north pole is closer to the elongate member than the south pole is to the elongate member.

The current flow direction of the first coil may be the winding direction of the first coil; and the current flow direction of the second coil may be the winding direction of the second coil. The first transducer and second transducer may be electromagnetic acoustic transducers, EMATs.

The first transducer and the second transducer may be configured to convert vibrations in the elongate member into received electrical signals in the first coil and the second coil, and/or to convert electrical signals in the first coil and the second coil into vibrations in the elongate member. The first transducer and the second transducer may be separated spatially. The first magnet may be a permanent magnet and the second magnet may be a permanent magnet.

The transducer array may further comprise electromagnetic shielding. The first transducer may comprise inner electromagnetic shielding substantially surrounding the first coil. The second transducer may comprise inner electromagnetic shielding substantially surrounding the second coil. The transducer array may comprise outer electromagnetic shielding substantially surrounding the first transducer and the second transducer.

The first transducer array may have a front surface which is shaped to match a surface of the elongate member. The first transducer and the second transducer may each be individually addressable. The first magnet may be a magnet array composing a first magnet portion and a second magnet portion, wherein the first coil is wound around the first portion and the second magnet portion is outside the coil.

According to various, but not necessarily all, examples there is provided a method for manufacturing a transducer array for guided wave testing of an elongate member. The method comprises: providing a first magnet; winding a first coil around the first magnet; providing a second magnet; and winding a second coil around the second magnet; wherein the first magnet and the second magnet have substantially opposite magnetic field orientations, and wherein the first coil and the second coil have substantially opposite current flow directions.

According to various, but not necessarily all, examples there is provided a transducer comprising: a magnet array comprising a first magnet portion, a second magnet portion, and a third magnet portion; and a coil wound around the first magnet portion substantially parallel to a first plane. The first magnet portion, second magnet portion, and third magnet portion have substantially the same magnetic field orientations. The second magnet portion and the third magnet portion are positioned at least partially in the first plane, outside of the coil, on opposite sides of the first magnet portion.

The first magnet portion, second magnet portion, and third magnet portion may be neighboring magnet portions and may be substantially positioned in a straight or curved line. The first magnet portion, second magnet portion, and third magnet portion may be substantially aligned. The transducer may be configured to couple to an elongate member for guided wave testing of the elongate member. The transducer may be configured such that when the transducer is coupled to the elongate member the first magnet portion, second magnet portion, and third magnet portion are substantially aligned in a direction parallel to, or perpendicular to, the length of the elongate member. The first magnet portion, second magnet portion, and third magnet portion may be substantially level.

The second magnet portion and the first magnet portion may be positioned apart by less than the size of the longest dimension of either magnet portion. The third magnet portion and the first magnet portion may be positioned apart by less than the size of the longest dimension of either magnet portion.

The transducer may further comprise a housing. The magnet array and the coil may be positioned within the housing. The second magnet portion and the third magnet portion may each be exposed to the housing with nothing there between.

The transducer may further comprise electromagnetic shielding. The first magnet portion and the coil may be positioned within the electromagnetic shielding.

The coil may be wound around an axis of winding, and the second magnet portion and the third magnet portion may be positioned outside of the coil on opposite sides of the first magnet portion in a direction perpendicular to the axis of winding.

The first magnet portion, second magnet portion, and third magnet portion may be permanent magnets. The second magnet portion, and third magnet portion may be a pair and may be substantially identical. The first magnet portion may be elongate. The magnet array may be elongate. The magnet array has a height, a length and a width, and the first magnet portion, second magnet portion, and third magnet portion may have substantially the same height and substantially the same width.

The transducer may be for testing of a member. The shapes and/or sizes of the magnet portions are optimised according to the magnetic fields of the magnet portions, the member, and/or a testing frequency. The first magnet portion, second magnet portion, and third magnet portion may have substantially the same magnetic field orientations. The transducer may be an electromagnetic acoustic transducer, EMAT.

The second magnet portion may be separated spatially from the first magnet portion, and the third magnet portion may be separated spatially from the first magnet portion. A separation from the second magnet portion to the first magnet portion may be substantially similar in size to a separation from the third magnet portion to the first magnet portion.

The second magnet portion may be contiguous with the first magnet portion, and the third magnet portion may be contiguous with the first magnet portion. The magnet array may be a one piece member.

The magnet array may be configured such that the coil is wound around the first magnet portion so as to pass though the magnet array. The magnet array may comprise two holes positioned on opposite sides of the first magnet portion. The magnet array may be configured such that the coil is wound around the first magnet portion so as to pass though the holes.

The magnet array may comprise a central magnet and an outer frame surrounding the central magnet, wherein the central magnet is the first magnet portion, and wherein the outer frame comprises the second magnet portion and the third magnet portion. A transducer array for testing of a member may comprise at least: a first transducer and a second transducer.

According to various, but not necessarily all, examples there is provided a method for manufacturing a transducer. The method comprises: providing a magnet array comprising a first magnet portion, a second magnet portion, and a third magnet portion; winding a coil around the first magnet portion, the winding direction being substantially parallel to a first plane; and positioning the second magnet portion and the third magnet portion at least partially in the first plane, outside of the coil, on opposite sides of the first magnet portion.

According to various, but not necessarily all, examples there is provided examples as claimed in the appended claims.

While the above examples of the disclosure and optional features are described separately, it is to be understood that their provision in all possible combinations and permutations is contained within the disclosure. It is to be understood that various examples of the disclosure can comprise any or all of the features described in respect of other examples of the disclosure, and vice versa. Also, it is to be appreciated that any one or more or all of the features, in any combination, may be implemented by/comprised in/performable by an apparatus, a method, and/or computer program instructions as desired, and as appropriate.

BRIEF DESCRIPTION

Some examples will now be described with reference to the accompanying drawings in which: FIG. 1 illustrates a first example of a transducer positioned next to an elongate structure; FIG. 2 illustrates a first example of a transducer array positioned next to an elongate structure; FIG. 3 illustrates a second example of a transducer array positioned around an elongate structure; FIG. 4 illustrates an example of a system for guided wave testing; FIGs 5a, 5b, and 5c illustrate perspective and cross sectional views of a third example of a transducer; FIGs 6a and 6b illustrate cross sectional views of a fourth example of a transducer; FIG. 7 illustrates a fifth example of a transducer positioned next to an elongate structure; FIG. 8 illustrates a perspective view of a sixth example of a transducer; FIG. 9 illustrates a seventh example of a transducer; FIG. 10 illustrates an eighth example of a transducer; FIG. 11 illustrates a ninth example of a transducer positioned next to an elongate structure; FIG. 12 illustrates a tenth example of a transducer; FIG. 13 illustrates an eleventh example of a transducer; FIG. 14 illustrates an twelfth example of a transducer; FIG. 15 illustrates an example method; and FIG. 16 illustrates another example method.

The figures are not necessarily to scale. Certain features and views of the figures can be shown schematically or exaggerated in scale in the interest of clarity and conciseness. For example, the dimensions of some elements in the figures can be exaggerated relative to other elements to aid explication. Similar reference numerals are used in the figures to designate similar features. For clarity, all reference numerals are not necessarily displayed in all figures.

DETAILED DESCRIPTION

FIG. 1 illustrates a first example of a transducer 100 according to embodiments of the disclosure. The transducer 100 is positioned next to an elongate member 10, outside the elongate member 10, and is for guided wave testing of the elongate member 10. The transducer 100 is configured to couple to the elongate member 10 for guided wave testing of the elongate member 10.

The elongate member / structure 10 is a test specimen 10 for the transducer 100. The elongate structure 10 may be a pipe, a rail track, a rod, a cable or another elongate structure. In some examples the elongate member 10 may comprise curves, comprise changes in cross section or geometry along its length and/or be branched.

The transducer 100 comprises a magnet 110 and a coil 120 wound around the magnet 110. The magnet 110 produces a biasing magnetic field for the coil 120.

In some examples the transducer 100 is an acoustic transducer, such as an electromagnetic acoustic transducer (EMAT). The transducer 100 is for reception and/or transmission of signals. In some examples, the transducer 100 is configured to convert vibrations in the elongate member 10 into received electrical signals in the coil 120 and/or to convert electrical signals in the coil 120 into vibrations in the elongate member 10. The transducer 100 may be for nondestructive testing (NDT) of conductive structures 10. The transducer 100 may be for condition monitoring of the elongate member 10.

Coordinate axes 50 are illustrated in FIGs 1 and 2 that include an x axis, a y axis and a z axis. The y dimension is aligned with the length of the elongate member 10, the x dimension is aligned with the width of the elongate member 10, and the z dimension is aligned with the height of the elongate member 10. The x, y, and z dimensions are orthogonal to each other.

The magnet 110 comprises a north magnetic pole 112, and a south magnetic pole 114.

In some examples, the magnet 110 is a permanent magnet 110 and in some examples the magnet 110 is ferromagnetic. In some examples the magnet 110 is an electromagnet. A magnetic axis 116 of the magnet 110 is defined from the north magnetic pole 112 to the south magnetic pole 114.

The magnet 110 has a length, a height and a width. The height is parallel to the magnetic axis 116 from the north 112 to south 114 magnetic poles. In the illustrated example, the height of the magnet 110 is parallel to the z dimension, the length is parallel to the y dimension and the width is parallel to the x dimension.

The illustrated magnet 110 is elongate, the length is greater than the height, and the length is greater than the width. The illustrated magnet 110 is bar shaped and has a the length that is twice or more the size of the width. An elongate magnet 110 leads to a more uniform magnetic flux field in the elongate member 10 improving sensitivity of testing.

In other examples the magnet 110, may be a different shape and might not be elongate.

The coil 120 is an electromagnetic coil 120, and in the example of FIG. 1 is a coil 120 of wire. The illustrated coil 120 comprises two turns 122. In other examples, different number of turns 122 may be wound around the magnet 110.

The coil 120 has a winding direction which may be the direction of movement of electric charge around the coil 120. The winding direction is perpendicular to the axis of winding. In some examples, the winding direction is the direction around the coil 120 from a positive electrode to a negative electrode, and the winding direction is clockwise or anti-clockwise.

The coil 120 has a current flow direction which is the direction of movement of current around the coil 120. The current flow direction is perpendicular to the axis of winding. In some examples, the current flow direction is the direction around the coil 120 from a positive electrode to a negative electrode, and the current flow direction is clockwise or anti-clockwise. In some examples the current flow direction is the winding direction.

In this example, the coil 120 is wound around the magnet 110 with an axis of winding substantially perpendicular to a magnetic axis 116 of the magnet 110 from the north magnetic pole 112 to the south magnetic pole 114. The coil 120 is wound around the magnet 110 substantially parallel to a plane at least partially defined by the magnetic axis 116. The coil 120 may be wound at least partially around the height of the magnet 110. The illustrated coil 120 is wound around the length and height of the magnet 110. The illustrated magnet 110 is substantially concentric to the coil 120.

In some examples, the coil 120 has helical winding, in other examples the coil 120 may have a different winding, such as orthocyclic winding. In some examples, the coil 120 is part of a flexible printed circuit board of coils. Both ends of the coil 120 are connected to electrical connectors 124, which connect to other circuitry, such as electrical terminals.

Although the illustrated transducer 100, is positioned above the elongate member 10, in other examples, the transducer 100 may be located at different positions. In some examples, where multiple transducers 100 are coupled to the elongate member 10, the transducers 100 may be positioned around the perimeter / circumference of the elongate member 10. In some examples, the transducer 100 may be positioned inside the elongate member 10, such as inside a pipe 10. In some examples, multiple transducers 100 are positioned around the inner surface of a pipe 10.

In the some examples, when the transducer 100 is coupled to the elongate member 10, the magnetic axis 116 for the magnet 110 is substantially perpendicular to a surface of the elongate member 10. When the transducer 100 is coupled to the elongate member 10, the coil 120 is wound around the magnet 110 with an axis of winding substantially perpendicular to the outer surface of the elongate member 10.

In the illustrated example, when the transducer 100 is coupled to the elongate member 10, the coil 120 is wound around the magnet 110 with an axis of winding substantially perpendicular to the length of the elongate member 10, and the magnetic axis 116 is substantially perpendicular to the length of the elongate member 10. However, in other examples, different orientations are possible, as, for example, in FIG. 7.

FIG. 2 illustrates a first example of a transducer array 250 according to embodiments of the invention. The transducer array 250 is positioned next to an elongate structure 10. FIG. 2 illustrates a perspective which is perpendicular to the perspective illustrated in FIG. 1.

The illustrated transducer array 250 is for guided wave testing of an elongate member 10 and is configured to couple to the elongate member 10 for guided wave testing of the elongate member 10. The illustrated transducer array 250 comprises a first transducer 100 and a second transducer 200.

The first transducer 100 and second transducer 200 of the transducer array 250 illustrated in FIG. 2 may comprise some or all of the features of the first example of a transducer 100 illustrated in FIG. 1. The first transducer 100 and second transducer of the transducer array are similar to the first example of a transducer 100 with a number of differences.

The first transducer 100 comprises a first magnet 110 and a first coil 120 wound around the first magnet 110. The second transducer 200 comprises a second magnet 210 and a second coil 220 wound around the second magnet. The first transducer 100 and second transducer 200 of the transducer array 250 are neighboring transducers 100, 200. They may be similar to each other and may form a pair.

The first magnet 110 and the second magnet 210 have substantially opposite magnetic field orientations / polarities. As such the magnetic axes 116, 216 the first magnet 110 and the second magnet 210 are substantially opposite to each other. Additionally, the first coil 120 and the second coil 220 have substantially opposite winding directions and current flow directions.

In the illustrated example, the magnetic field orientations of the first magnet 110 and the second magnet 210 are close to but not completely opposite. However, in other examples the magnetic field orientations of the first magnet 110 and the second magnet 210 are completely opposite. In the illustrated example, the current flow directions of the first coil 120 and the second coil 220 are close to but not completely opposite. However, in other the current flow directions of the first coil 120 and the second coil 220 are completely opposite.

In this example, with respect to the surface of the elongate member 10, the first magnet and the second magnet 210 have substantially opposite magnetic field orientations, and the first coil 120 and the second coil 220 have substantially opposite current flow directions.

In the illustrated transducer array 250, the north magnetic pole 112 of the first magnet is closer to the south magnetic pole 214 of the second magnet 210 than it is to the north magnetic pole 212 of the second magnet 210.

In the illustrated example, when the transducer array 250 is coupled to the elongate member 10, a magnetic axis 116 for the first magnet 110, defined from the north magnetic pole 112 to the south magnetic pole 114, is substantially perpendicular to a surface of the elongate member 10, and a magnetic axis 216 for the second magnet 210, defined from the north magnetic pole 212 to the south magnetic pole 214, is substantially perpendicular to a surface of the elongate member 10.

In the illustrated example, the magnetic axis 116 for the first magnet 110 points towards the elongate member 10, and the magnetic axis 216 for the second magnet 210 points away from the elongate member 10. When the transducer array 250 is coupled to the elongate member 10, for the first magnet 110 the south pole 114 is closer to the elongate member 10 than the north pole 112 is to the elongate member 10, and for the second magnet 210 the north pole 212 is closer to the elongate member 10 than the south pole 214 is to the elongate member 10.

In the example of FIG. 2, the first transducer 100 and the second transducer 200 are separated spatially. The first magnet 110 and the second magnet 210 are separated spatially, and the first coil 210 and the second coil 220 are separated spatially.

In the illustrated transducer array 250 there is a gap, such as an air gap, between the first transducer 100 and the second transducer 200, and between the transducer array 250 and the elongate member 10.

In some examples the transducer array 250 comprises feet for contacting the elongate member 10 to help maintain the relative position of the transducer array 250 and the elongate member 10. In some examples the feet are comprised of a non-conductive material such as a foam. For example, a closed cell polymer foam interlayer such as Foamex. In other examples, the feet are comprised of a conductive material such as a metal, for example metal springs. The feet may be designed, through geometry and/or material choice, to cause as little effect as possible on the propagation of ultrasound in the elongate member 10.

In some examples, the transducer array 250 does not contact the elongate member 10. In such examples the transducer array 250 may be supported by hanging or magnetic levitation.

The first transducer 100 and second transducer 200 may be electrically coupled. For example, the first transducer 100 and second transducer 200 may be connected in series. The first transducer 100 and second transducer 200 may be considered to form a linear array 250. In other examples, the first transducer 100 and second transducer 200 are not connected in series.

In some examples, the first transducer 100 and the second transducer 200 are configured to convert vibrations in the elongate member 10 into received electrical signals in the first coil 120 and the second coil 220, and/or to convert electrical signals in the first coil 120 and the second coil 220 into vibrations in the elongate member 10. In some examples, the first transducer 100 and the second transducer 200 are each individually addressable and have separate signal channels.

FIG. 3 illustrates a second example of a transducer array 350 according to the embodiments of the disclosure. The transducer array 350 is positioned around an elongate structure 10.

The second example of a transducer array 350 illustrated in FIG. 3 may comprise some or all of the features of the first example of a transducer array 250 illustrated in FIG. 2.

The second example of a transducer array 350 is similar to the first example of a transducer array 250 with a number of differences.

The illustrated transducer array 350 comprises a plurality of transducers 100, 200 comprising the first transducer 100 and the second transducer 200. In this example, the transducer array 350 comprises eight transducers 100, 200. In other examples, the transducer array 350 comprises a different number of transducers 100, such as four or more transducers 100, 200.

When the transducer array 350 is coupled to the elongate member 10, the plurality of transducers 100, 200 are positioned at least partially around a perimeter of the elongate member 10. In the illustrated example the plurality of transducers 100, 200 are positioned circumferentially around the perimeter of the elongate member 10.

The illustrated plurality of transducers 100, 200 are positioned at substantially the same distance from the elongate member 10. The illustrated plurality of transducers 100, 200 are substantially equally spaced around the perimeter of the elongate member 10. The transducers 100, 200 may be considered to be rotationally offset from one another.

Each of the transducers 100, 200 may comprise some or all of the features of the first and second examples of a transducer 100, 200 of FIGs 1 and 2.

In the example of FIG. 3, the plurality of transducers 100, 200 have alternating magnetic field orientations, and alternating coil 120, 220 current flow directions. The magnetic field orientations, and coil 120, 220 current flow directions, are alternating from the perspective of the elongate member 10. The magnetic field orientations, and coil 120, 220 current flow directions, are alternating in the sense that neighbouring transducers 100, 200 have substantially opposite magnetic field orientations, and coil 120, 220 current flow directions with respect to the elongate member 10.

In the illustrated example, the magnetic axis 116, 216 for the magnets 110, 220 alternates between pointing towards the elongate member 10 and pointing away from the elongate member 10. The coils' 120, 220 axes of winding alternate between pointing clockwise and anticlockwise around the elongate member 10.

The coil 120, 220 current flow directions alternate between pointing clockwise and anticlockwise around their respective magnets 110, 220 in line with the magnetic axis 116, 216. This can be seen from the positive and negative symbols of the coils 120, 220.

Alternating magnetic polarities and coil 120, 220 current flow directions creates a multipolar magnet system around the elongate member 10. This has the advantage of causing the magnetic field strength and flux density to be maximized allowing for better penetration of the elongate member 10 than would be the case if the magnetic polarities and coil 120, 220 current flow directions did not alternate. It also ensures that the elongate member 10 experiences the same Lorentz force vector from each transducer 100, 200. This allows Lorentz forces to be more uniformly distributed throughout the elongate member 10.

The orientation of the coils 120, 220 relative to the magnet 110, 210 also leads to better penetration into the elongate member 10.

FIG. 4 illustrates an example of a system 400 for guided wave testing according to embodiments of the disclosure.

In the illustrated system 400, a digital twin 402 of the system 400 provides information to a user equipment 404 which sends and receives signals from a pulser-receiver 406. The user equipment 404 may have a graphical user interface. The pulser-receiver 406 comprises a waveform generator 408 and a receiver 410, and sends signals through a power amplifier 412 and multiplexor 414 to a first transducer array 350a.

The first transducer array 350a transmits signals, such as ultrasonic signals, through a test specimen / elongate member 10. Subsequently, a second transducer array 350c detects the signals in the test specimen 10 after they have traveled along the test specimen 10. The received signals will differ from the transmitted signals and will vary depending on the specimen 10 and any defects present.

The second transducer array 350c sends signals through a multiplexor 416 and pre amplifier 418 to the pulser receiver 406 which then sends the signals to the user equipment 404 to be analysed.

Although the transmitting transducer array 350a and the receiving transducer array 350c are illustrated as different arrays 350a, 350c, in other examples they may be the same transducer array 350. This may involve the system 400 operating in a pulse echo configuration.

In examples where there are separate transmitting and receiving transducer arrays 350a, 350c. The transducer arrays 350a, 350c may be optimized for transmitting or receiving. For example a receiving transducer array 350c may use very thin wire with a large number of turns 122.

The example of a transducer array 350a, 350c illustrated in FIG. 4 may comprise some or all of the features of the first and second examples of a transducer array 250, 350 illustrated in FIGs 2 and 3. The example of a transducer array 350a, 350c illustrated in FIG. 4 is similar to the first and second examples of a transducer array 250, 350 with a number of differences.

The illustrated transducer arrays 350a, 350c each comprise four transducers 100, 200. The illustrated transducers 100, 200 comprise a magnet 110, 210 a coil 120, 220, a former / support 115, 225 and a transducer enclosure / housing 125, 225.

The former / support 115, 125 may be positioned at least partially between the magnet 110, 210 and coil 120, 220 and helps to hold the coil 120, 220 in place as it is wound around the magnet. The transducer housing 125, 225 may substantially surround the magnet 110, 210 and coil 120, 220.

In some examples, the transducer housing 125, 225 comprises electromagnetic shielding. In some examples separate electromagnetic shielding may be present.

The illustrated transducer arrays 350a, 350c also comprise an array enclosure / housing 355 which may substantially surround the transducers 100, 200 and any transducer housing 125, 225. The array housing 355 may comprise electromagnetic shielding.

In some examples, the transducer array 350a, 350c comprises electromagnetic shielding. The first transducer 100 may comprise inner electromagnetic shielding 125 substantially surrounding the first coil 120, and the second transducer 200 may comprise inner electromagnetic shielding 225 substantially surrounding the second coil 220. In some examples, the transducer array 350a, 350c comprises outer electromagnetic shielding 355 substantially surrounding the first transducer 100 and the second transducer 200. The outer electromagnetic shielding 355 may substantially surround the inner electromagnetic shielding 125, 225. This double shielding reduces coupling between neighbouring transducers 100, 200 and neighbouring transducer arrays 350a, 350c and so reduces noise.

FIGs 5a, 5b, and 5c illustrate perspective and cross sectional views of a third example of a transducer 500 according to embodiments of the disclosure. FIG. 5a illustrates a perspective view of the transducer 500. FIGs 5b, and 5c illustrate cross sectional views of the transducer 500. The cross sectional planes 20, 30 of FIGs 5b, and 5c are illustrated as rectangles in FIG. 5a. In use, the upper surface 530 of the transducer 500 faces towards the elongate member 10.

The third example of a transducer 500 may comprise some or all of the features of the first and second examples of a transducer 100, 200 illustrated in FIGs 1 to 4. The third example of a transducer 500 is similar to the first and second examples of a transducer 100, 200 with a number of differences.

The illustrated transducer 500 comprises a former / support 115 and a housing 125. The support 115 helps to maintain the position of the coil 120 relative to the magnet 110 and may act as a bobbin for the coil 120. The support 115 may comprise any suitable material such as plastic. The illustrated support 115 is substantially non-conductive.

The support 115 can also change the spacing of the magnet 110 and coil 120. In the illustrated example, the spacing between the magnet 110 and coil 120 is larger on the side which would face away from the elongate member 10, than the side which would face towards the elongate member 10. This has the effect of reducing the transduction of waves in other bodies surrounding the magnet 110, such as the housing 125, which reduces noise.

In this example, the housing 125 substantially surrounds the magnet 110 and coil 120.

However, the illustrated housing 125 has an opening on the side 530 which would face the elongate member. This side 530 is substantially open. The housing 125 may comprise any suitable material, for a example a metal, such as steel or aluminium, or a plastic. The housing 125 may function as electromagnetic shielding. In some examples, anchor lugs can be used to connect the coil 120 to the housing 125 to reduce strain on the coil 120. The illustrated housing 125 has a clamshell design, however other forms of housing 125 may be used.

The illustrated transducer 500 has a front surface 530 which is shaped to match a surface of the elongate member 10. In same examples the front surface 530 has a profiled shape to match a profiled surface of the elongate member 10. In some examples the front surface 530 has a curved shape to match a curved surface of the elongate member 10. This can reduce electromagnetic field ingress to the transducer 500 from other sources, and can reduce electromagnetic field egress from the transducer 500, reducing noise. In some examples the transducer 500 and/or transducer array 350 is configured and shaped to receive signals from the elongate member 10.

FIGs 6a and 6b illustrate cross sectional views of a fourth example of a transducer 600

according to embodiments of the disclosure.

The fourth example of a transducer 600 may comprise some or all of the features of the first, second and third examples of a transducer 100, 200, 500 illustrated in FIGs 1 to 5. The fourth example of a transducer 600 is similar to the third example of a transducer 500 with a number of differences.

In FIGs 6a and 6b, the magnet 110 has opposite magnetic polarity / field orientations to the example of FIGs 5a to 5c. As such the north pole 112 of the magnet 110 is closer to the front surface 530 of the transducer 600, and would be closer to the elongate member 10 when the transducer 600 is coupled to the elongate member 10.

In the illustrated example, the coil 120 comprises a plurality of turns 122, specifically eighteen turns 122, and the turns 122 form a plurality of layers, specifically three layers.

In other examples the coil 120 may comprise different numbers of turns 122 and layers.

FIG. 7 illustrates a fifth example of a transducer 700 according to embodiments of the invention. The transducer 700 is positioned next to an elongate structure 10.

The fifth example of a transducer 700 may comprise some or all of the features of the first, second, third and fourth examples of a transducer 100, 200, 500, 600 illustrated in FIGs 1 to 6. The fifth example of a transducer 700 is similar to the first example of a transducer 100 with a number of differences.

In the example of FIG. 7 the transducer 700 is positioned at a different orientation to the elongate member 10 than in FIG. 1. As such, in the example of FIG. 7 when the transducer 700 is coupled to the elongate member 10, the coil 120 is wound around the magnet 110 with an axis of winding substantially parallel to the length of the elongate member 10.

In FIG. 1, the transducer 100 is configured to cause propagation of torsional waves (shear waves) along the length of the elongate member 10. In FIG. 7, the transducer 700 is configured to cause propagation of longitudinal waves (compression waves) propagate along the length of the elongate member 10. The choice of orientation, and thus wave mode, affects the data that can be collected.

FIG. 8 illustrates a perspective view of a sixth example of a transducer 800 according to embodiments of the disclosure. In the illustrated transducer 800, the magnet 110, coil 120, and support 115 have been partially lifted out of the housing 125 for visibility.

The transducer 800 is depicted amongst other housings 125 for other transducers 800, some with and some without supports 115.

The sixth example of a transducer 800 may comprise some or all of the features of the first, second, third, fourth and fifth examples of a transducer 100, 200, 500, 600, 700 illustrated in FIGs 1 to 7. The sixth example of a transducer 800 is similar to the third and fourth examples of a transducer 500, 600 with a number of differences as can be seen in FIG. 8.

Extended Magnet Transducer FIGs 9 to 14 illustrate examples of transducers 900, 1000, 1100, 1200, 1300, 1400 in which multiple magnet portions 920, 940, 960 are present. The multiple magnet portions 920, 940, 960 can be considered to form an extended magnet.

FIG. 9 illustrates a seventh example of a transducer 900 according to embodiments of the invention. The seventh example of a transducer 900 may comprise some or all of the features of the first, second, third, fourth, fifth and sixth examples of a transducer 100, 200, 500, 600, 700, 800 illustrated in FIGs 1 to 8. The seventh example of a transducer 900 may be an acoustic transducer, such as an electromagnetic acoustic transducer, EMAT. The transducer 900 may form part of a transducer array 250, 350.

In some examples, the seventh example of a transducer 900 is for guided wave testing. In other examples, the seventh example of a transducer 900 might not be for guided wave testing. The transducer 900 may be used in a different form of testing, for example other forms of ultrasonic testing such as time of flight diffraction (TOFT) or phased array ultrasonic testing (PAUT). In other examples, transducer 900 may be used within a linear actuator or measurement device.

In some examples, the seventh example of a transducer 900 is for testing of an elongate member 10. In other examples, the transducer 900 is for testing of different test specimens / members 10 which might not be elongate.

The illustrated transducer 900 comprises a magnet array 910 and a coil 120. The magnet array 910 comprises a first magnet portion 920, a second magnet portion 940, and a third magnet portion 960. The illustrated first magnet portion 920, second magnet portion 940, and third magnet portion 960 have substantially the same magnetic field orientations / polarities.

The illustrated first magnet portion 920, second magnet portion 940, and third magnet portion 960 are permanent magnets.

In some examples, the first magnet portion 920 is a permanent magnet and the second magnet portion 940 and third magnet portion 960 are not permanent magnets. For example, the second magnet portion 940 and third magnet portion 960 may comprise ferromagnetic materials, such as pure iron, soft iron, low carbon steel, or ferrite. In other examples, the first magnet portion 920 is not a permanent magnet and the second magnet portion 940 and third magnet portion 960 are permanent magnets.

The coil 120 is wound around the first magnet portion 920. The second magnet portion 940 and the third magnet portion 960 do not have coils wound around them.

In this example, the coil 120 is wound around the first magnet portion 920 substantially parallel to a first plane 60. The second magnet portion 940 and the third magnet portion 960 are positioned at least partially in the first plane 60, outside of the coil 120, on opposite sides of the first magnet portion 920. In FIG. 9, the first plane 60 is illustrated side-on as a dotted line.

In this example, the coil 120 is wound around an axis of winding, and the second magnet portion 940 and the third magnet portion 960 are positioned outside of the coil 120 on opposite sides of the first magnet portion 920 in a direction perpendicular to the axis of winding. The illustrated coil 120 comprises two turns 122. In other examples, different number of turns 122 may be wound around the first magnet portion 910.

In a transducer 900 for testing of a test specimen 10, a magnet 110 being longer in the lengthwise/axial dimension improves the uniformity of magnetic flux. On the other hand, it is advantageous for the extent of the coil 120 in the axial dimension to be short so as to avoid frequency dependent behaviour caused by changing ratios of wavelength to transducer 900 size. Embodiments of the disclosure provide both of these advantages by winding the coil 120 around a first magnet portion 920 and having further magnet portions 940, 960 outside of the coil 120. This, in effect allows the magnet 110 / magnet array 910 to extend beyond the coil 120 and be longer than the coil 120.

In the illustrated example, the first magnet portion 920, second magnet portion 940, and third magnet portion 960 are neighboring magnet portions 920, 940, 960. They are substantially positioned in a line, are substantially aligned, and are substantially level.

In other examples, however, the magnet portions 920, 940, 960 may have a different configurations. For example, they may be positioned in a curved line instead of a straight line. In some examples, the magnet portions 920, 940, 960 are positioned in curved line to match a curved surface of the test specimen 10.

In the example of FIG. 9 the second magnet portion 940, and third magnet portion 960 are a pair, are substantially the same size and are substantially identical.

In the illustrated example, the first magnet portion 920 is elongate, and the magnet array 910 is elongate. The magnet array 910 has a height parallel to the z axis, a length parallel to the y axis and a width parallel to the x axis. The illustrated first magnet portion 920, second magnet portion 940, and third magnet portion 960 have substantially the same height and substantially the same width. The illustrated first magnet portion 920 is longer than the second magnet portion 940, and third magnet portion 960.

In other examples, the magnet portions 920, 940, 960 may have different sizes, shapes and/or positions. In some examples, the shapes and/or sizes of the magnet portions 920, 940, 960 are optimised according to the magnetic fields of the magnet portions 920, 940, 960, the member / specimen 10, and/or a testing signal frequency.

In the illustrated example, the second magnet portion 940 is separated spatially from the first magnet portion 920, and the third magnet portion 960 is separated spatially from the first magnet portion 920. That is to say there are gaps between the magnet portions 920, 940, 960. The separation from the second magnet portion 940 to the first magnet portion 920 is substantially similar in size to a separation from the third magnet portion 960 to the first magnet portion 920. In this example the first magnet portion 920, second magnet portion 940 and third magnet portion 960 are not contiguous with each other.

In the illustrated example, the magnet portions 920, 940, 960 are positioned close together. The second magnet portion 940 and the first magnet portion 920 are positioned apart by less than the size of the longest dimension of either magnet portion 920, 940. The third magnet portion 960 and the first magnet portion 920 are positioned apart by less than the size of the longest dimension of either magnet portion 920, 960.

In some examples, the second magnet portion 940 and the first magnet portion 920 are positioned apart by less than 50%, such as less than 25%, of the size of the longest dimension of any of the magnet portions 920, 940, 960; and the third magnet portion 960 and the first magnet portion 920 are positioned apart, by less than 50%, such as less than 25%, of the size of the longest dimension of any of the magnet portions 920, 940, 960.

In some examples, the second magnet portion 940 and the first magnet portion 920 are positioned less than 10 mm apart, and the third magnet portion 960 and the first magnet portion 920 are positioned less than 10 mm apart. For example, the second magnet portion 940 and the first magnet portion 920 are positioned less than 5 mm apart, such as less than 2 mm apart, and the third magnet portion 960 and the first magnet portion 920 are positioned less than 5 mm apart, such as less than 2mm apart.

FIG. 10 illustrates an eighth example of a transducer 1000 according to embodiments of the invention. The eighth example of a transducer 1000 may comprise some or all of the features of the first, second, third, fourth, fifth, sixth and seventh examples of a transducer 100, 200, 500, 600, 700, 800, 900 illustrated in FIGs 1 to 9. The eighth example of a transducer 1000 is similar to the seventh example of a transducer 900 with a number of differences.

In this example, the transducer 1000 is positioned next to a test specimen / elongate member 10. The transducer 1000 is configured to convert vibrations in the test specimen 10 into received electrical signals in the coil 120, and/or to convert electrical signals in the coil 120 into vibrations in the test specimen 10.

In some examples, the transducer 1000 is configured to couple to the elongate member 10 for guided wave testing of the elongate member 10, and the transducer 1000 is configured such that when the transducer 1000 is coupled to the elongate member 10, the first magnet portion 920, second magnet portion 940, and third magnet portion 960 are substantially aligned in a direction parallel to the length of the elongate member 10.

The first magnet portion 920, second magnet portion 940, and third magnet portion 960 each have north magnetic poles 922, 942, 962 and south magnetic poles 924, 944, 964. The magnetic axes 116 of the magnet portions 920, 940, 960, from the north magnetic pole 922, 942, 962 to the south magnetic pole 924, 944, 964 are substantially aligned.

In this example, the coil 120 is wound around the first magnet portion 920 with an axis of winding substantially perpendicular to the magnetic axis 116 of the first magnet portion 920. The illustrated coil 120 is wound around the first magnet portion 920 with an axis of winding substantially perpendicular to the length of the elongate member 10.

FIG. 11 illustrates a ninth example of a transducer 1100 according to embodiments of the invention. The ninth example of a transducer 1100 may comprise some or all of the features of the first, second, third, fourth, fifth, sixth, seventh and eighth examples of a transducer 100, 200, 500, 600, 700, 800, 900, 1000 illustrated in FIGs 1 to 10. The ninth example of a transducer 1100 is similar to the seventh and eighth examples of a transducer 900, 1000 with a number of differences.

In this example when the transducer 1100 is coupled to the elongate member 10, the first magnet portion 920, second magnet portion 940, and third magnet portion 960 are substantially aligned in a direction perpendicular to the length of the elongate member 10. In some examples, the magnet portions 920, 940, 960 are aligned in a straight line.

In other examples, the magnet portions 920, 940, 960 are aligned in a curved line which may follow the curvature of the test specimen 10.

FIG. 12 illustrates a tenth example of a transducer 1200 according to embodiments of the invention. The tenth example of a transducer 1200 may comprise some or all of the features of the first, second, third, fourth, fifth, sixth, seventh, eighth and ninth examples of a transducer 100, 200, 500, 600, 700, 800, 900, 1000, 1100 illustrated in FIGs 1 to 12. The tenth example of a transducer 1200 is similar to the seventh, eighth and ninth examples of a transducer 900, 1000, 1100 with a number of differences.

The illustrated transducer 1200 comprises a housing 125 and a support / former 115 in a similar manner to the examples of FIGs 5a to 6b. The magnet array 910 and coil 120 are positioned within the housing 125. The illustrated second magnet portion 940 and the third magnet portion 960 are each exposed to the housing 125 with nothing there between. In some examples the housing 125 comprises electromagnetic shielding 125. In some examples the transducer 1200 may comprise separate electromagnetic shielding.

In the example of FIG. 12, the first magnet portion 920 and the coil 120 are positioned within the housing 125 and within the electromagnetic shielding 125. The second magnet portion 940 and third magnet portion 960 are positioned at least partially outside the housing 125 and electromagnetic shielding 125. In other examples the second magnet portion 940 and third magnet portion 960 are positioned within the housing 125 and/or the electromagnetic shielding 125.

FIG. 13 illustrates an eleventh example of a transducer 1300 according to embodiments of the invention. The eleventh example of a transducer 1300 may comprise some or all of the features of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth and tenth examples of a transducer 100, 200, 500, 600, 700, 800, 900, 1000, 1100, 1200 illustrated in FIGs 1 to 12.

The illustrated transducer 1300 comprises a first magnet portion 920, a second magnet portion 940, and a third magnet portion 960. In this example, the second magnet portion 940 is contiguous with the first magnet portion 920, and the third magnet portion 960 is contiguous with the first magnet portion 920. The illustrated magnet array 910 is a one piece member and is integrally formed.

In this example, the magnet array 910 comprises two holes 1302, 1304 positioned on opposite sides of the first magnet portion 920. The illustrated holes 1302, 1304 are through holes and are substantially level. The coil 120 is wound around the first magnet portion 920 so as to pass though the holes 1302, 1304 and so as to pass though the magnet array 910. The illustrated holes 1302, 1304 have a circular cross section. In other examples the holes 1302, 1304 may have a different cross sectional shape such as square.

The holes 1302, 1304 in FiIG. 13 correspond to the gaps between magnet portions 920, 940, 960 in FIGs 9 to 12. However, in this example the holes 1302, 1304 extend all the way though the magnet array 910 in only the x dimension, whereas in the examples of FIGs 9 to 12 the gaps extend all the way though the magnet array 910 in both the x and z dimensions.

FIG. 14 illustrates a twelfth example of a transducer 1400 according to embodiments of the invention. The twelfth example of a transducer 1400 may comprise some or all of the features of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth and eleventh examples of a transducer 100, 200, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300 illustrated in FIGs 1 to 13. The twelfth example of a transducer 1400 is similar to the eleventh example of a transducer 1300 with a number of differences.

The illustrated magnet array 910 comprises a central magnet / magnet portion 1406 and an outer frame 1408 surrounding the central magnet 1406. The outer frame 1408 is magnetic and may be a permanent magnet. The outer frame 1408 comprises a recess 1410 for receiving the central magnet 1406. The illustrated recess 1410 is contiguous with the holes 1302, 1304. In some examples the recess 1410 is a through hole. The illustrated magnetic frame 1408 is a one piece member and is integrally formed, in other examples the frame 1408 may be comprised of multiple pieces.

In some examples, the central magnet 1406 is a permanent magnet and outer frame 1408 is not a permanent magnet. For example, the outer frame 1408 may comprise ferromagnetic materials, such as pure iron, soft iron, low carbon steel, or ferrite. In other examples, the central magnet 1406 is not a permanent magnet and the outer frame 1408 is a permanent magnet.

In some examples, the frame 1408 is designed to augment the biasing magnetic field to optimally enhance (i.e., extend and improve) the magnetic field experienced by the elongate member 10.

The central magnet 1406 can be removed. This improves the ease of winding of the coil 120 around the central magnet 1406. The central magnet 1406 may then be inserted into the magnetic frame 1408. In some examples, the central magnet 1406 is held by the frame 1408 in a friction fit. In some examples, the central magnet 1406 and outer frame 1408 are connected together by a connector such as a mechanical connector/fastener or adhesive.

The first magnet portion 920 comprises the central magnet 1406 and may be considered to comprise part of the outer frame 1408. The outer frame 1408 comprises the second magnet portion 940 and the third magnet portion 960 and may be considered to comprise part of the first magnet portion 920.

In a different consideration, the central magnet 1406 may be the first magnet portion 920 and the outer frame 1408 may comprise the second magnet portion 940 and the third magnet portion 960. In this interpretation the second magnet portion 940 and the third magnet portion 960 may be contiguous.

FIG. 15 illustrates an example method 1500 according to examples of the disclosure. The method 1500 is a method for manufacturing a transducer array 250, 350 for guided wave testing of an elongate member 10.

At block 1502, a first magnet 110 is provided. At block 1504, a first coil 120 is wound around the first magnet 110. At block 1506, a second magnet 210 is provided. At block 1508, a second coil 220 is wound around the second magnet 210. The first magnet 110 and the second magnet 210 have substantially opposite magnetic field orientations, and first coil 120 and the second coil 220 have substantially opposite current flow directions.

FIG. 16 illustrates an example method 1600 according to examples of the disclosure. The method 1600 is a method for manufacturing a transducer 900, 1000, 1100, 1200, 1300, 1400.

At block 1602, a magnet array 910 is provided. The magnet array 910 comprising a first magnet portion 920, a second magnet portion 940, and a third magnet portion 960. The first magnet portion 920, second magnet portion 940, and third magnet portion 960 may have substantially the same magnetic field orientations.

At block 1604, a coil 120 is wound around the first magnet portion 920, the winding direction being substantially parallel to a first plane 60.

At block 1606, the second magnet portion 940 and the third magnet portion 960 are positioned at least partially in the first plane 60, outside of the coil 120, on opposite sides of the first magnet portion 920.

The blocks illustrated in the accompanying FIGs may represent steps in a method, the illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some blocks to be omitted.

Where a structural feature has been described, it may be replaced by means for performing one or more of the functions of the structural feature whether that function or those functions are explicitly or implicitly described.

Elements described may be operationally coupled and any number or combination of intervening elements can exist (including no intervening elements).

The term 'comprise' is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use 'comprise' with an exclusive meaning then it will be made clear in the context by referring to "comprising only one..." or by using "consisting".

In this description, the wording 'connect', 'couple' and 'communication' and their derivatives mean operationally connected/coupled/in communication. It should be appreciated that any number or combination of intervening components can exist (including no intervening components), i.e., so as to provide direct or indirect connection/coupling/communication. Any such intervening components can include hardware and/or software components.

As used herein, the term "determine/determining" (and grammatical variants thereof) can include, not least: calculating, computing, processing, deriving, measuring, investigating, identifying, looking up (for example, looking up in a table, a database or another data structure), ascertaining and the like. Also, "determining" can include receiving (for example, receiving information), accessing (for example, accessing data in a memory), obtaining and the like. Also, "determine/determining" can include resolving, selecting, choosing, establishing, and the like.

In this description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term 'example' or 'for example' or 'can' or 'may' in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus 'example', 'for example', 'can' or 'may' refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all of the instances in the class. It is therefore implicitly disclosed that a feature described with reference to one example but not with reference to another example, can where possible be used in that other example as part of a working combination but does not necessarily have to be used in that other example.

Although examples have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the claims.

Features described in the preceding description may be used in combinations other than the combinations explicitly described above.

Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

Although features have been described with reference to certain examples, those features may also be present in other examples whether described or not.

The term 'a', 'an' or 'the' is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising a/an/the Y indicates that X may comprise only one Y or may comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use 'a', 'an' or 'the' with an exclusive meaning then it will be made clear in the context. In some circumstances the use of 'at least one' or 'one or more' may be used to emphasis an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning.

The presence of a feature (or combination of features) in a claim is a reference to that feature or (combination of features) itself and also to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that perform substantially the same function, in substantially the same way to achieve substantially the same result.

In this description, reference has been made to various examples using adjectives or adjectival phrases to describe characteristics of the examples. Such a description of a characteristic in relation to an example indicates that the characteristic is present in some examples exactly as described and is present in other examples substantially as described.

The above description describes some examples of the present disclosure however those of ordinary skill in the art will be aware of possible alternative structures and method features which offer equivalent functionality to the specific examples of such structures and features described herein above and which for the sake of brevity and clarity have been omitted from the above description. Nonetheless, the above description should be read as implicitly including reference to such alternative structures and method features which provide equivalent functionality unless such alternative structures or method features are explicitly excluded in the above description of the examples of the present disclosure.

Whilst endeavoring in the foregoing specification to draw attention to those features believed to be of importance it should be understood that the Applicant may seek protection via the claims in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not emphasis has been placed thereon.

I/we claim:

Claims

CLAIMS1. A transducer array for guided wave testing of an elongate member, the transducer array comprising: a first transducer comprising: a first magnet; and a first coil wound around the first magnet; and a second transducer comprising: a second magnet; and a second coil wound around the second magnet; wherein the first magnet and the second magnet have substantially opposite magnetic field orientations, and wherein the first coil and the second coil have substantially opposite current flow directions.
2. The transducer array of claim 1, wherein the transducer array is configured to couple to the elongate member for guided wave testing of the elongate member.
3. The transducer array of claim 1 or 2, wherein the transducer array comprises a plurality of transducers comprising the first transducer and the second transducer.
4. The transducer array of claim 3, wherein the transducer array is configured such that when the transducer array is coupled to the elongate member, the plurality of transducers are positioned around the perimeter of the elongate member.
5. The transducer array of claim 3 or 4, wherein the plurality of transducers have alternating magnetic field orientations, and alternating current flow directions.
6. The transducer array of any of the preceding claims, wherein the first coil is wound around the first magnet with an axis of winding substantially perpendicular to a magnetic axis of the first magnet from the north magnetic pole to the south magnetic pole, and the second coil is wound around the second magnet with an axis of winding substantially perpendicular to a magnetic axis of the first magnet from the north magnetic pole to the south magnetic pole.
7. The transducer array of any of the preceding claims, wherein the first coil is wound around the first magnet substantially parallel to a plane at least partially defined by a magnetic axis from the north magnetic pole to the south magnetic pole of the first magnet, and the second coil is wound around the second magnet substantially parallel to a plane at least partially defined by a magnetic axis from the north magnetic pole to the south magnetic pole of the second magnet.
8. The transducer array of any of the preceding claims, wherein the first magnet has a length, a height and a width, wherein the height is parallel to the magnetic axis from the north to south magnetic pole, wherein the first coil is wound around the length and height of the first magnet; wherein the second magnet has a length, a height and a width, wherein the height is parallel to the magnetic axis from the north to south magnetic pole, and wherein the second coil is wound around the length and height of the second magnet.
9. The transducer array of claim 8, wherein the length of the first magnet is twice or more the size of the width of the first magnet, and wherein the length of the second magnet is twice or more the size of the width of the second magnet.
10. The transducer array of any of the preceding claims, wherein a magnetic axis for the first magnet, defined from the north magnetic pole to the south magnetic pole, is substantially opposite to a magnetic axis for the second magnet, defined from the north magnetic pole to the south magnetic pole.
11. The transducer array of any of the preceding claims, wherein the north magnetic pole of the first magnet is closer to the south magnetic pole of the second magnet than it is to the north magnetic pole of the second magnet.
12. The transducer array of any of claims 2 to 11, wherein the transducer array is configured such that when the transducer array is coupled to the elongate member, a magnetic axis for the first magnet, defined from the north magnetic pole to the south magnetic pole, is substantially perpendicular to a surface of the elongate member, and a magnetic axis for the second magnet, defined from the north magnetic pole to the south magnetic pole, is substantially perpendicular to a surface of the elongate member.
13. The transducer array of any of claims 2 to 12, wherein the transducer array is configured such that when the transducer array is coupled to the elongate member, for the first magnet the south pole is closer to the elongate member than the north pole is to the elongate member, and for the second magnet the north pole is closer to the elongate member than the south pole is to the elongate member.
14. The transducer array of any of the preceding claims, wherein the current flow direction of the first coil is the winding direction of the first coil; and wherein the current flow direction of the second coil is the winding direction of the second coil.
15. The transducer array of any of the preceding claims, wherein the first transducer and second transducer are electromagnetic acoustic transducers, EMATs.
16. The transducer array of any of the preceding claims, wherein the first transducer and the second transducer are configured to convert vibrations in the elongate member into received electrical signals in the first coil and the second coil, and/or to convert electrical signals in the first coil and the second coil into vibrations in the elongate member.
17. The transducer array of any of the preceding claims, wherein the first transducer and the second transducer are separated spatially.
18. The transducer array of any of the preceding claims, wherein the first magnet is a permanent magnet and the second magnet is a permanent magnet.
19. The transducer array of any of the preceding claims, further comprising electromagnetic shielding.
20. The transducer array of claim 19, wherein the first transducer comprises inner electromagnetic shielding substantially surrounding the first coil, wherein the second transducer comprises inner electromagnetic shielding substantially surrounding the second coil.
21. The transducer array of claim 19 or 20, wherein the transducer array comprises outer electromagnetic shielding substantially surrounding the first transducer and the second transducer.
22. The transducer array of claim 21, wherein the first transducer array has a front surface which is shaped to match a surface of the elongate member.
23. The transducer array of any of the preceding claims, wherein the first transducer and the second transducer are each individually addressable.
24. The transducer array of any of the preceding claims wherein the first magnet is a magnet array composing a first magnet portion and a second magnet portion, wherein the first coil is wound around the first portion and the second magnet portion is outside the coil.
25. A method for manufacturing a transducer array for guided wave testing of an elongate member, the method comprising: providing a first magnet; winding a first coil around the first magnet; providing a second magnet; and winding a second coil around the second magnet; wherein the first magnet and the second magnet have substantially opposite magnetic field orientations, and wherein the first coil and the second coil have substantially opposite current flow directions.