Electricity: measuring and testing – Of geophysical surface or subsurface in situ – For small object detection or location
Patent
1989-10-30
1991-04-09
Strecker, Gerard R.
Electricity: measuring and testing
Of geophysical surface or subsurface in situ
For small object detection or location
116209, 138104, 324 67, 324345, 335303, 405157, 350 9623, G01V 308, G01V 3165, H01F 100, F16L 5500
Patent
active
050068067
ABSTRACT:
In order to locate, trace, and identify hidden elongated objects, such as buried fiber optic cables, the objects are provided with elongated permanent magnet identifier devices having magnetic fields that may be detected at a distance from the objects. In one embodiment the identifier device comprises an elongated strip magnetized in the direction of its width and formed into a long-pitch helix, producing a characteristic "magnetic field signature" that enhances detection and identification of the object, as by a portable gradiometer that is moved over the surface of the earth along a line generally parallel to the length of the object. This embodiment may provide a magnetic field that diminishes as the square of the distance from the identifier device (rather than the usual cube of the distance), thereby enabling detection at substantial distances. In a second embodiment distinctive magnetic field signatures are produced by arrays of spaced permanent magnets, the fields of which add and subtract to provide resultant magnetic fields with peaks and valleys along a line generally parallel to the length of the object.
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Osman Bradley L.
Rippingale John B.
Schonstedt Erick O.
Upton Charles R.
Schonstedt Instrument Company
Strecker Gerard R.
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