# US 10,502,714 B2 · Electro-magnetic acoustic transducer (EMAT) for both lamb and shear horizontal wave transduction > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,502,714 B2 - Document ID: US10502714B2 - Status: Granted - Kind: B2 - Application number: 15/719,022 - Filed: 2017-09-28 - Published: 2019-03-28 - Granted: 2019-12-10 - Earliest claimed: 2017-09-28 - Assignees: ULC Robotics, Inc. - Applicants: ULC Robotics, Inc. - Inventors: Baiyang Ren; Junjun Xin - Web page: https://patentgrep.com/patent/US10502714B2 ## CPC - G01N 29/2412: {using the magnetostrictive properties of the material to be examined, e.g. electromagnetic acoustic transducers [EMAT]; (investigating the presence of flaws using eddy currents G01N27/90, magnetostrictive transducers B06B1/08, measuring magnetostrictive properties G01R33/18)} - G01N 2291/0422: Shear waves, transverse waves, horizontally polarised waves - G01N 2291/0427: Flexural waves, plate waves, e.g. Lamb waves, tuning fork, cantilever - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract An electro-magnetic acoustic transducer (EMAT) generates both Lamb waves and shear horizontal (SH) waves or Lamb waves only. In configurations, the EMAT includes first and second coils shifted in alignment relative to one another and a magnet array overlaid over the coils. The EMAT generates a Lamb wave when the first coil is excited with an electrical current and generates a SH wave when the second coil is excited with an electrical current. In other configurations, the EMAT includes a coil and a magnet array which are movable relative to one another between a first position and a second position shifted in alignment relative to one another. The EMAT generates a Lamb wave when the coil is excited with an electrical current while in the first position and generates a SH wave when the coil is excited with an electrical current while in the second position. ## Claims ### Claim 1 An electro-magnetic acoustic transducer comprising: a magnet array having a plurality of magnets with alternating polarizations, the magnets being arranged in columns and rows so that the alternating polarizations form a checkerboard pattern; a first coil placed relative to the magnet array such that legs of a coil segment of the first coil extend parallel to a first direction across the rows of the checkerboard pattern of alternating polarizations and are positioned along respective boundaries between adjacent pairs of columns of the checkerboard pattern of alternating polarizations, wherein for each leg of the first coil positioned along a respective boundary between an adjacent pair of columns of the checkerboard pattern, a magnet of the magnet array is in one of the adjacent pair of columns of the checkerboard pattern on one side of the respective boundary in a given row of the checkerboard pattern and another magnet of the magnet array having an opposite polarization is in the other one of the adjacent pair of columns of the checkerboard pattern on the other side of the respective boundary in the given row of the checkerboard pattern; a second coil placed relative to the magnet array such that legs of a coil segment of the second coil extend parallel to the first direction across the rows of the checkerboard pattern of alternating polarizations and are positioned along respective center lines of columns of the checkerboard pattern of alternating polarizations, wherein for each leg of the second coil positioned along a respective center line of a column of the checkerboard pattern, a magnet of the magnet array is in the column of the checkerboard pattern with a portion of the magnet being on one side of the respective center line in a given row of the checkerboard pattern and a remaining portion of the same magnet being on the other side of the respective center line in the given row of the checkerboard pattern; and wherein a Lamb wave is generated when the first coil is excited with an electrical current and a shear horizontal wave is generated when the second coil is excited with an electrical current. ### Claim 2 (depends on 1) The electro-magnetic acoustic transducer of claim 1 wherein: the legs of the coil segment of the first coil have a coil spacing between them and the legs of the coil segment of the second coil have the coil spacing between them; and the coil segment of the second coil is offset from the coil segment of the first coil by a half of the coil spacing. ### Claim 3 (depends on 1) The electro-magnetic acoustic transducer of claim 1 further comprising: a printed circuit board; and wherein the first coil is on a first layer of the printed circuit board and the second coil is on a second layer of the printed circuit board. ### Claim 4 (depends on 3) The electro-magnetic acoustic transducer of claim 3 wherein: the magnet array is overlaid over the printed circuit board. ### Claim 5 (depends on 1) The electro-magnetic acoustic transducer of claim 1 wherein: the first coil includes a plurality of coil segments, each leg of the coil segments of the first coil extending parallel to the first direction across the rows of the checkerboard pattern of alternating polarizations and being positioned along respective boundaries between ad′ acent pairs of columns of the checkerboard pattern of alternating polarizations. ### Claim 6 (depends on 5) The electro-magnetic acoustic transducer of claim 5 wherein: the second coil includes a plurality of coil segments, each leg of the coil segments of the second coil extending parallel to the first direction across the rows of the checkerboard pattern of alternating polarizations and being positioned along respective center lines of columns of the checkerboard pattern of alternating polarizations. ### Claim 7 (depends on 1) The electro-magnetic acoustic transducer of claim 1 wherein: the magnets of the magnet array are block shaped, stepped magnets conforming to a curvature of a non-planar surface. ### Claim 8 (depends on 1) The electro-magnetic acoustic transducer of claim 1 wherein: the magnets of the magnet array form an arc segment conforming to a curvature of a non-planar surface. ### Claim 9 (depends on 1) The electro-magnetic acoustic transducer of claim 1 wherein: the magnets of the magnet array have a rectangular footprint. ### Claim 10 (depends on 1) The electro-magnetic acoustic transducer of claim 1 wherein: the magnets of the magnet array have a square footprint. ### Claim 11 An electro-magnetic acoustic transducer comprising: a magnet array having a plurality of magnets with alternating polarizations, the magnets being arranged in columns and rows so that the alternating polarizations form a checkerboard pattern; a coil; wherein at least one of the magnet array and the coil is movable between (i) a first position in which the coil is placed relative to the magnet array such that legs of a coil segment of the coil extend parallel to a first direction across the rows of the checkerboard pattern of alternating polarizations and are positioned along respective boundaries between adjacent pairs of columns of the checkerboard pattern of alternating polarizations, wherein for each leg of the coil positioned along a respective boundary between an adjacent pair of columns of the checkerboard pattern, a magnet of the magnet array is in one of the adjacent pairs of columns of the checkerboard pattern on one side of the respective boundary in a given row of the checkerboard pattern and another magnet of the magnet array having an opposite polarization is in the other one of the adjacent pair of columns of the checkerboard pattern on the other side of the respective boundary in the given row of the checkerboard pattern, and (ii) a second position in which the coil is placed relative to the magnet array such that the legs of the coil segment of the coil extend parallel to the first direction across the rows of the checkerboard pattern of alternating polarizations and are positioned along respective center lines of columns of the checkerboard pattern of alternating polarizations, wherein for each leg of the coil positioned along a respective center line of a column of the checkerboard pattern, a magnet of the magnet array is in the column with a portion of the magnet being on one side of the respective center line in a given row of the checkerboard pattern and a remaining portion of the same magnet being on the other side of the respective center line in the given row of the checkerboard pattern; and wherein a Lamb wave is generated when the coil is excited with an electrical current while in the first position and a shear horizontal wave is generated when the coil is excited with an electrical current while in the second position. ### Claim 12 (depends on 11) The electro-magnetic acoustic transducer of claim 11 wherein: the legs of the coil segment of the coil have a coil spacing between them; and the first position and the second position are offset from one another by a half of the coil spacing. ### Claim 13 (depends on 11) The electro-magnetic acoustic transducer of claim 11 further comprising: a printed circuit board; wherein the coil is on a layer of the printed circuit board; and wherein the magnet array is overlaid over the printed circuit board. ### Claim 14 (depends on 11) The electro-magnetic acoustic transducer of claim 11 wherein: the coil includes a plurality of coil segments, each leg of the coil segments of the coil extending parallel to the first direction across the rows of the checkerboard pattern of alternating polarizations and being positioned along respective boundaries between adjacent pairs of columns of the checkerboard pattern of alternating polarizations when the coil is placed relative to the magnet array in the first position, and each leg of the coil segments of the coil extending parallel to the first direction across the rows of the checkerboard pattern of alternating polarizations and being positioned along respective center lines of columns of the checkerboard pattern of alternating polarizations when the coil is placed relative to the magnet array in the second position. ### Claim 15 (depends on 11) The electro-magnetic acoustic transducer of claim 11 wherein: the magnets of the magnet array have a rectangular footprint. ### Claim 16 (depends on 11) The electro-magnetic acoustic transducer of claim 11 further comprising: an actuator configured to move at least one of (i) the magnet array relative to the coil and (ii) the coil relative to the magnet array. ### Claim 17 An electro-magnetic acoustic transducer comprising: a magnet array having a plurality of magnets with alternating polarizations, the magnets being arranged in columns and rows so that the alternating polarizations form a checkerboard pattern; a coil placed relative to the magnet array such that legs of a coil segment of the coil extend parallel to a first direction across the rows of the checkerboard pattern of alternating polarizations and are positioned along respective boundaries between adjacent pairs of columns of the checkerboard pattern of alternating polarizations, wherein for each leg of the coil positioned along a respective boundary between an adjacent pair of columns of the checkerboard pattern, a magnet of the magnet array is in one of the adjacent pairs of columns of the checkerboard pattern on one side of the respective boundary in a given row of the checkerboard pattern and another magnet of the magnet array having an opposite polarization is in the other one of the adjacent pair of columns of the checkerboard pattern on the other side of the respective boundary in the given row of the checkerboard pattern; and wherein a Lamb wave is generated when the coil is excited with an electrical current. ### Claim 18 (depends on 17) The electro-magnetic acoustic transducer of claim 17 wherein: the magnets of the magnet array have a rectangular footprint. ### Claim 19 An electro-magnetic acoustic transducer comprising: a magnet array having a plurality of magnets with alternating polarizations, the magnets being arranged in columns and rows so that the alternating polarizations form a checkerboard pattern; a coil; a magnetic conducting material layer between the magnet array and the coil, the magnetic conducting material layer configured to direct the checkerboard pattern of alternating polarizations of the magnet array to (i) a first position in which the coil is placed relative to the magnet array such that legs of a coil segment of the coil extend parallel to a first direction across the rows of the checkerboard pattern of alternating polarizations and are positioned along respective boundaries between adjacent pairs of columns of the checkerboard pattern of alternating polarizations, wherein for each leg of the coil positioned along a respective boundary between an adjacent pair of columns of the checkerboard pattern, a magnet of the magnet array is in one of the adjacent pair of columns of the checkerboard pattern on one side of the respective boundary in a given row of the checkerboard pattern and another magnet of the magnet array having an opposite polarization is in the other one of the adjacent pair of columns of the checkerboard pattern on the other side of the respective boundary in the given row of the checkerboard pattern, and (ii) a second position in which the coil is placed relative to the magnet array such that the legs of the coil segment of the coil extend parallel to the first direction across the rows of the checkerboard pattern of alternating polarizations and are positioned along respective center lines of columns of the checkerboard pattern of alternating polarizations, wherein for each leg of the coil positioned along a respective center line of a column of the checkerboard pattern, a magnet of the magnet array is in the column of the checkerboard pattern with a portion of the magnet being on one side of the respective center line in a given row of the checkerboard pattern and a remaining portion of the same magnet being on the other side of the respective center line in the given row of the checkerboard pattern; and wherein a Lamb wave is generated when the coil is excited with an electrical current while in the first position and a shear horizontal wave is generated when the coil is excited with an electrical current while in the second position. ### Claim 20 (depends on 19) The electro-magnetic acoustic transducer of claim 19 wherein: at least one of the magnet array and the coil is movable (i) for the coil to be placed relative to the magnet array such that legs of a coil segment of the coil extend parallel to a first direction across the rows of the checkerboard pattern of alternating polarizations and are positioned along respective boundaries between adjacent pairs of columns of the checkerboard pattern of alternating polarizations and (ii) for the coil to be placed relative to the magnet array such that the legs of the coil segment of the coil extend parallel to the first direction across the rows of the checkerboard pattern of alternating polarizations and are positioned along respective center lines of columns of the checkerboard pattern of alternating polarizations.