Apparatus and method for eddy-current scanning of a surface to detect cracks and other defects
First Claim
1. An apparatus comprising:
- a sensor unit having a plurality of electromagnetic sensing coils;
an excitation/sensing circuit that generates an AC excitation signal, wherein the excitation/sensing circuit includes a differential amplifier;
a plurality of reference coils including a first reference coil and a second reference coil, wherein the first reference coil is configured for a first type of metal and the second reference coil is configured for a second type of metal different from the first type;
a first circuit that includes a multiplexer that at some first period of time electrically connects a first sensing coil selected from the plurality of sensing coils to a first input of the differential amplifier and through a predetermined impedance to the AC excitation signal; and
a second circuit that at the first period of time selectively connects one of the plurality of reference coils to a second input of the differential amplifier, wherein the excitation/sensing circuit is configured to demodulate a first signal from the first sensing coil and the first reference coil in order to detect a phase change, an amplitude change, or both phase and amplitude changes due to a magnetic anomaly of an object being scanned.
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Accused Products
Abstract
An apparatus having a plurality of coils (e.g., numerous thin-film coils formed in an array on a flex circuit), each coil acting as an excitation unit that generates an alternating excitation magnetic signal; and as a sensor configured to detect an eddy-current signal'"'"'s phase and amplitude changes relative to the excitation magnetic signal. In some embodiments, the apparatus electronically scans a surface (e.g., of a metal plate) by successively switching to individual ones of the plurality of excitation/sensing coils (using, e.g., an analog multiplexer) without physical movement in order to detect anomalous signal changes in a manner that reduces signal changes due to probe lift-off relative to the surface. In some embodiments, the coils are placed across a large area of interest, for inspection of a large surface area in a few seconds without moving the apparatus. This can provide high-sensitivity detection and an accurate indication of flaw locations.
130 Citations
37 Claims
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1. An apparatus comprising:
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a sensor unit having a plurality of electromagnetic sensing coils; an excitation/sensing circuit that generates an AC excitation signal, wherein the excitation/sensing circuit includes a differential amplifier; a plurality of reference coils including a first reference coil and a second reference coil, wherein the first reference coil is configured for a first type of metal and the second reference coil is configured for a second type of metal different from the first type; a first circuit that includes a multiplexer that at some first period of time electrically connects a first sensing coil selected from the plurality of sensing coils to a first input of the differential amplifier and through a predetermined impedance to the AC excitation signal; and a second circuit that at the first period of time selectively connects one of the plurality of reference coils to a second input of the differential amplifier, wherein the excitation/sensing circuit is configured to demodulate a first signal from the first sensing coil and the first reference coil in order to detect a phase change, an amplitude change, or both phase and amplitude changes due to a magnetic anomaly of an object being scanned. - View Dependent Claims (2, 3, 4)
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5. An apparatus comprising:
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a sensor unit having a plurality of electromagnetic coils; an excitation/sensing circuit that generates an AC excitation signal, wherein the excitation/sensing circuit includes a differential amplifier; a multiplexer that, at a first period of time, selectively electrically connects a first coil selected from the plurality of coils through a first predetermined impedance to the AC excitation signal; and a source of a first reference signal, wherein at the first period of time the first coil is selectively connected to a first input of the differential amplifier and the first reference signal is connected to a second input of the differential amplifier, wherein at some second period of time, a second coil selected from the plurality of coils is selectively connected by the multiplexer to the AC excitation signal through the first predetermined impedance, and is selectively connected to the first input of the differential amplifier and the first reference signal is connected to the second input of the differential amplifier, and wherein the excitation/sensing circuit is configured to demodulate a first signal from the first coil in order to detect phase and/or amplitude changes due to a magnetic anomaly of an object being scanned. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method comprising:
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providing a plurality of thin-film sensing coils in an array on a substrate; providing a plurality of thin-film reference coils; selecting a first sensing coil from the plurality of thin-film sensing coils and establishing an analog electrical connection to the selected first sensing coil; driving the first sensing coil with an AC excitation signal through a first predetermined impedance to obtain a first sensed signal; selecting a first one of the plurality of reference coils and at a first period of time, establishing an analog electrical connection to the selected first reference coil and driving the first reference coil with an AC excitation signal through a second predetermined impedance to obtain a first reference signal; demodulating the first sensed signal, wherein the demodulating of the first sensed signal includes differentially amplifying a difference between the first sensed signal and the first reference signal at the first period of time in order to detect a phase change, an amplitude change, or both phase and amplitude changes due to a magnetic anomaly of an object being scanned; and selecting, and at a second period of time, driving a second reference coil with an AC excitation signal through the second predetermined impedance to obtain a second reference signal; and
wherein the demodulating of the first sensed signal includes differentially amplifying the second reference signal relative to the first sensed signal to obtain a differential signal at the second period of time.
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17. A method comprising:
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providing a plurality of thin-film coils in an array on a substrate formed as a thin-film two-dimensional array of coils on a flexible substrate; placing the thin-film array in a substantially fixed position on a metallic object during inspection of a two-dimensional area of the object such that each respective coil of the plurality of coils measures an electromagnetic condition of a portion of the two-dimensional area of the metallic object adjacent that respective coil; selecting a first coil from the plurality of thin-film coils and establishing an analog electrical connection to the selected first coil; driving the first coil with an AC excitation signal through a first predetermined impedance to obtain a first sensed signal; obtaining a first reference signal; demodulating the first sensed signal in order to detect phase and/or amplitude changes due to a magnetic anomaly of an object being scanned, wherein the demodulating of the first sensed signal includes differentially amplifying the first reference signal relative to the first sensed signal to obtain a differential signal at some first period of time; at some second period of time, selecting a second coil from the plurality of coils; driving the second coil with the AC excitation signal through the first predetermined impedance to obtain a second sensed signal; and differentially amplifying the first reference signal relative to the second sensed signal to obtain a differential signal at some second period of time. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. An apparatus comprising:
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a plurality of thin-film coils in an array on a substrate; a plurality of thin-film reference coils; means for selecting a first sensing coil from the plurality of thin-film sensing coils and establishing an analog electrical connection to the selected first sensing coil; means for driving the first sensing coil with an AC excitation signal through a first predetermined impedance to obtain a first sensed signal; means for selecting a first one of the plurality of thin-film reference coils and for, at a first period of time, establishing an analog electrical connection to the selected first reference coil and for driving the first reference coil with an AC excitation signal through a second predetermined impedance to obtain a first reference signal; means for demodulating the first sensed signal, wherein the means for demodulating the first sensed signal includes means for differentially amplifying a difference between the first sensed signal and the first reference signal at the first period of time in order to detect phase and/or amplitude changes due to a magnetic anomaly of an object being scanned; and means for selecting and for, at a second period of time, driving a second reference coil with an AC excitation signal through the second predetermined impedance to obtain a second reference signal; and
wherein the means for demodulating of the first sensed signal includes means for differentially amplifying the second reference signal relative to the first sensed signal to obtain a differential signal at the second period of time.
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28. An apparatus comprising:
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a plurality of thin-film coils in a two-dimensional array on a substrate means for placing the thin-film array in a substantially fixed position on a metallic object during inspection of a two-dimensional area of the object such that each respective coil of the plurality of coils measures an electromagnetic condition of a portion of the two-dimensional area of the metallic object adjacent that respective coil; means for selecting a first coil from the plurality of thin-film coils and establishing an analog electrical connection to the selected first coil; means for driving the first coil with an AC excitation signal through a first predetermined impedance to obtain a first sensed signal; means for obtaining a first reference signal; means for demodulating the first sensed signal in order to detect phase and/or amplitude changes due to a magnetic anomaly of an object being scanned, wherein the demodulating of the first sensed signal includes differentially amplifying the first reference signal relative to the first sensed signal to obtain a differential signal at some first period of time; means for selecting, at some second period of time, a second coil from the plurality of coils; means for driving the second coil with the AC excitation signal through a second predetermined impedance to obtain a second sensed signal; and means for differentially amplifying the first reference signal relative to the second sensed signal to obtain a differential signal at some second period of time. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37)
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Specification