Patent ID: 9651471
Date: 2017-05-16
CPC Classifications: G01N

Claim:
1. A method for detecting defects in a ferromagnetic material, the method comprising: disposing a plurality of magnetometers about a surface of the ferromagnetic material, wherein each magnetometer of the plurality of magnetometers is fixed in position, relative to the ferromagnetic material; using the plurality of magnetometers to sense a magnetic field generated by the ferromagnetic material at a first point in time; generating data points of a first two-dimensional map from the sensed magnetic field, each data point corresponding to a respective location on the surface of the ferromagnetic material and representing strength of the sensed magnetic field proximate the location at the first point in time; using the plurality of magnetometers to sense the magnetic field generated by the ferromagnetic material at a second point in time, later than the first point in time, generating data points of a second two-dimensional map from the sensed magnetic field, each data point corresponding to a respective location on the surface of the ferromagnetic material and representing strength of the sensed magnetic field proximate the location at the second point in time; subtracting the data points of the second two-dimensional map from spatially corresponding data points of the first two-dimensional map, thereby yielding a difference two-dimensional map; identifying, in the difference two-dimensional map, a plurality of data points that conform to a predefined spatial pattern of magnetic field strength; and outputting a location proximate the surface of the ferromagnetic material that corresponds to the plurality of data points.