EMAT with integral electrostatic shield

摘要

A shield for an electromagnetic acoustic transducer (EMAT) has multiple layers of electrically insulating and electrically conductive materials which contain a coil of the EMAT. A first insulating layer lies directly on top of the coil and is attached thereto by a suitable layer of non-conductive adhesive. A second layer having both insulating and conductive portions is provided on a side of the coil opposite the first insulating layer such that the coil is completely encapsulated within and in direct contact only with the insulating portions of the first and second layers. The insulating portion of the second layer has a high electrical resistance. A third, conductive layer having a conductive adhesive side is provided in contact with the conductive portion of the second layer. The third layer is also provided with a window extending completely therethrough having dimensions coextensive with those of the coil; shielding of the coil itself by this third layer is thus prevented. Finally, a fourth insulating layer preferably made of a thin layer of ultrahigh molecular weight polyethylene or similar insulating material is attached to the underlying third, conductive layer by adhesive means. An alternative shield and coil arrangement is also disclosed, wherein the coil is etched on one side of a substrate and a corresponding shield configuration is etched on the other side, resulting in an integrated shield and coil assembly for use in an electromagnetic acoustic transducer.