Patent ID: 7295003
Filing Date: 2007-11-13
Classification: G01N

Abstract:
1. An apparatus for detecting defects in the proximity of a hole of a laminate structure, the laminate structure having multiple layers, with at least one layer being composed of an electrically conductive material, the apparatus comprising: a generally cylindrical body portion having a diameter substantially close to the diameter of the hole for insertion into the hole; a first coil of wire wrapped about the cylindrical body portion such that, when the body portion is inserted into the hole, the first coil of wire resides in a plane substantially parallel to a first electrically conductive layer of the laminate material such that a magnetic field produced by the first coil of wire will produce eddy-currents in the first conductive layer in the plane of the first conductive layer; a reference-coil coupled to the first coil, the reference-coil having substantially the same electrical properties as the first coil; a reference shield in close proximity to the reference-coil, wherein the reference shield includes electrical properties substantially identical to the electrically conductive material layer of the laminate structure; and an impedance sensing device coupled to the first coil of wire and the reference-coil, wherein the impedance sensing device electrically excites the first coil and the reference coil to detect an impedance change of the first coil.