Electricity: measuring and testing – Magnetic – With means to create magnetic field to test material
Patent
1995-04-25
1997-04-08
O'Shea, Sandra L.
Electricity: measuring and testing
Magnetic
With means to create magnetic field to test material
324262, 324235, 324238, G01N 2782, G01R 3354
Patent
active
056191367
ABSTRACT:
An array of sensors is provided at or near the surface of a material arranged to detect magnetic flux leakage occurring when a magnetic field is induced in the material. The sensors in the array are coupled in respective pairs (differential pairs) such that when one partner of a respective pair overlies a discontinuity, a differential output signal is produced dependent on the difference between the output signals from the sensors of the respective differential pair. Because of the nature of the change of the flux leakage field produced by a discontinuity, respective partners of each pair of sensors are spaced relative to each other according to the invention. In one embodiment, partners of each sensor pair are spaced relative to one another both in the direction of travel of the apparatus and also in a direction transverse thereto. In another embodiment of the invention, each partner of a respective pair of sensors is spatially separated from the other partner of the respective pair by at least one partner of another pair of sensors. A warning is produced in response to the differential output signal to indicate that a discontinuity has been located. Typically the warning is only produced when the differential output signals are greater than a predetermined threshold value.
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Gordon David P.
O'Shea Sandra L.
Patidar Jay M.
Silverwing, Limited
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