Eddy current sensor arrays having drive windings with extended portions
First Claim
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1. A test circuit comprising:
- a primary winding loop of conducting segments having a linear extended portion to impose a magnetic field in a test material when driven by an electric current;
a first plurality of sense elements, positioned outside the primary loop near said extended portion, for sensing a response of the test material to the imposed magnetic field, the sense elements being aligned with one another to sense the response at incremental areas along a path parallel to the extended portion of the primary winding, having connection leads to each sense element and having separate output connections, and a second pair of non-connecting leads proximate to the connection leads.
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Abstract
An apparatus for the nondestructive measurements of materials. Eddy current sensing arrays are described which provide a capability for high resolution imaging of test materials and also a high probabilitity of detection for defects. These arrays incorporate layouts for the sensing elements which take advantage of microfabrication manufacturing capabilities for creating essentially identical sensor arrays, aligning sensing elements in proximity to the drive elements, and laying out conductive pathways that promote cancellation of undesired magnetic flux.
92 Citations
49 Claims
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1. A test circuit comprising:
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a primary winding loop of conducting segments having a linear extended portion to impose a magnetic field in a test material when driven by an electric current;
a first plurality of sense elements, positioned outside the primary loop near said extended portion, for sensing a response of the test material to the imposed magnetic field, the sense elements being aligned with one another to sense the response at incremental areas along a path parallel to the extended portion of the primary winding, having connection leads to each sense element and having separate output connections, and a second pair of non-connecting leads proximate to the connection leads. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A test circuit comprising:
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a primary winding loop of conducting segments having an extended portion and a return portion to impose a magnetic field in a test material when driven by an electric current; and
a first plurality of sense elements for sensing a response of the test material to the imposed magnetic field, said sense elements being positioned inside the primary loop near said extended portion and farther from the return portion, the sense elements being aligned with one another to sense the response at incremental areas along a path parallel to the extended portion of the primary winding and having separate output connections. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
a second plurality of sense elements oriented in parallel to the first plurality of sense elements.
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28. A test circuit as claimed in claim 27 wherein the first and second pluralities of sense elements are positioned on different sides of the extended portion for inspection of a fastener in an aircraft skin.
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29. A test circuit as claimed in claim 27 wherein said extended portion is linear.
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30. A test circuit as claimed in claim 27 wherein both the first and the second plurality of sense elements are located near the extended portion of the primary winding.
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31. A test circuit as claimed in claim 27 wherein distances between the first and second plurality of sense elements and the extended portion of the primary winding are equal.
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32. A test circuit as claimed in claim 27 wherein distances between the first and second plurality of sense elements and the extended portion of the primary winding are not equal.
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33. A test circuit as claimed in claim 27 wherein the second plurality of sense elements is positioned on the side opposite that of the first plurality of sense elements.
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34. A test circuit as claimed in claim 27 wherein multiple frequencies are used to remove the interference caused by a feature on the test material and isolate a flaw response with one frequency providing a response dominated by the feature and at least one additional frequency providing a response associated with the feature and the flaw.
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35. A test circuit as claimed in claim 27 wherein a shape filter is applied to each sense element response and a correlation is calculated between the sense element response and a characteristic response for a flaw.
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36. A test circuit as claimed in claim 35 wherein the responses from the two pluralities of sense elements on opposite sides of the extended portion are combined to construct a filtered response for a flaw of interest.
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37. A test circuit as claimed in claim 36 wherein the flaw of interest is a crack.
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38. A test circuit as claimed in claim 36 wherein the flaw of interest is a buried anomaly.
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39. A test circuit as claimed in claim 36 wherein the combination is a sum of the responses divided by a constant raised to a power of the difference of the responses.
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40. A test circuit as claimed in claim 36 wherein the responses for multiple frequencies are combined to construct a filtered response for the flaw of interest.
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41. A test circuit comprising:
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a primary winding loop of conducting segments having a pair of parallel extended portions to impose a magnetic field in a test material when driven by an electric current;
a first plurality of sense elements positioned closer to one extended portion of the pair of extended portions, each having separate output connections, for sensing a response of the test material to the imposed magnetic field, the sense elements being aligned with one another to sense the response at incremental areas along a path parallel to the extended portions of the primary winding, and a width of a sense element being smaller than a spacing between the parallel extended portions. - View Dependent Claims (42, 43, 44, 45, 46, 47, 48, 49)
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Specification