Inspection apparatus and method

A mobile anomaly detector operable to survey an electrically conductive object, said anomaly detector comprising:

• a shoe, said shoe having a sole for engagement with the object;
• an electromagnetic field emitter mounted within said shoe;
• said electromagnetic field emitter including a magnetic flux focusing core;
• said magnetic flux focusing core having first and second soles at said sole, said poles being spaced apart by a gap;
• a power source connected to drive said emitter, said power source being operable at a plurality of frequencies;
• said emitter being operable to induce an eddy current field in the object when said sole is placed adjacent thereto;
• a plurality of eddy current sensors arrayed adjacent said electromagnetic field emitter, members of said plurality of eddy current sensors including eddy current field divergence sensor coils, each of said eddy current field divergence sensor coils being operable to sense directly eddy field differential induced in the electrically conductive object, each of said eddy current field divergence sensor coils being located to monitor a different portion of the eddy current field at said sole adjacent to said electromagnetic field emitter;
• and
• at least one of (a) a recorder operable to store recording data from said eddy current sensors for subsequent signal processing operations;
• and (b) a processor operable to interpret data obtained from said eddy current sensors.

A hand portable eddy field anomaly detector for use in detecting anomalies in an electrically conductive object, said eddy field anomaly detector comprising:

• a magnetic field emitter operable to induce an eddy current field in an adjacent electrically conductive object to be examined;
• said magnetic field emitter including a magnetic flux focusing core;
• said magnetic flux focusing core having first and second poles for placement, in use, next to the electrically conductive object, said first and second poles being separated by a gap;
• sensing apparatus operable, while said anomaly detector is in one location, to sample, at first and second sensing regions of said gap, back EMF of the eddy current field;
• said sensing apparatus operable to sample at said first sensing region including a first eddy field divergence sensor coil operable to sense directly eddy field differential in the electrically conductive object;
• said first sensing region being different from said second sensing region;
• at least one of
• (a) a recorder operable to store data observed with respect to said first and second sensing regions;
• and
• (b) a signal processor operable to compare at least one of
• (i) data observed with respect to said first sensing region and data observed with respect to said second sensing region;
• and
• (ii) data observed with respect to at least one of said first and second sensing regions and a reference datum;
• and
• said first and second sensing regions satisfying at least one condition selected from the set of conditions consisting of
• (a) said first sensing region includes at least a portion not covered by said second sensing region, and said first and second sensing regions are non-concentric;
• (b) said first sensing region includes at least a portion not covered by said second sensing region, and said second sensing region includes at least another portion not covered by said first sensing region;
• and
• (c) said first and second sensing regions are non-concentric and at least one of said first and second sensing regions is eccentric relative to said magnetic field emitter. field emitter.

A method of detecting anomalies in an electrically conductive object, said method comprising the steps of:

• establishing a time varying eddy current field in the electrically conductive object using an electromagnetic field emitting member that includes a magnetic flux focusing core, said magnetic flux focusing core having first and second soles that are, in use, placed next adjacent to the electrically conductive object, said first and second poles being spaced apart by a gap;
• monitoring at least first and second regions of the eddy current field at the gap, the first and second regions of the eddy current field at the gap being non-coterminous and non-concentric, the step of monitoring including using a first eddy field divergence sensor coil associated with the first region of the eddy current field at the gap directly to sense eddy field differential in the electrically conductive object at the gap;
• and
• comparing at least one of
• (a) eddy currents monitored in said first region with eddy currents monitored in said second region;
• and
• (b) eddy currents monitored in both said first region and said second region with a reference standard for said first region and said second region respectively.

A process of detection of anomalies in an electrically conductive object, said process comprising:

• providing an anomaly detection apparatus having an electromagnetic field emitting member, said electromagnetic field emitting member including a flux focusing core that includes a first portion and a second portion;
• said first and second portions of said flux focusing core each having a respective proximal end and a distal end;
• said proximal end of said first portion and said proximal end of said second portion being linked together on a continuous magnetic core path,
• said distal end of said first portion and said distal end of said second portion being separated from each other by a gap and defining respective poles of said flux focusing core;
• a power source connected for powering said electromagnetic field emitting member,
• said power source being operable to cause said electromagnetic field emitting member to emit a time varying electromagnetic field;
• said power source having at least a first frequency and a second frequency;
• an array of electromagnetic field sensing members, the members of said array being mounted adjacent to said electromagnetic field emitting member, the field sensing members including a first eddy field divergence sensor coil operable directly to sense eddy field differential in the gap, adjacent to the electrically conductive object;
• monitoring circuitry connected to the members of said array,
• said monitoring circuitry being operable to sense variation of signals as between members of said array;
• and
• a processor operable to compare signals sensed at said members of said array in response to electromagnetic signals emitted at said first frequency and at said second frequency;
• passing said anomaly detection apparatus adjacent to the electrically conductive object with said distal ends of said first and second portions of said flux focusing core being positioned nearer to the electrically conductive object than said proximal ends of said first and second portions;
• and
• emitting electromagnetic field signals at more than one frequency from said electromagnetic field emitting member to cause eddy currents to be generated in the electrically conductive object;
• monitoring eddy currents sensed directly by the array of electromagnetic field sensing members at a plurality of positions at the gap;
• and
• comparing data monitored at the plurality of positions at the gap and at the first and second frequencies to provide an indication of the location of an anomaly in the electrically conductive object.

An anomaly detection apparatus for placement next to an electrically conductive object, said anomaly detection apparatus comprising:

• an electromagnetic field emitting member, said electromagnetic field emitting member including a magnetic flux focusing core;
• a power source connected to said electromagnetic field emitting member, said power source being operable to drive said electromagnetic field emitting member to emit a time varying electromagnetic field;
• said power source having at least first and second driving frequencies;
• an array of electromagnetic field sensing members, the members of said array being mounted adjacent to said electromagnetic field emitting member;
• said array including at least first and second field sensing members, said first and second field sensing members being oriented toward non-coincident regions adjacent to said field emitting member, at least said first electromagnetic field sensing member being non-concentric with said electromagnetic field emitting member, said first electromagnetic field sensing member including an eddy field divergence sensor coil operable to sense directly eddy field differential in the electrically conductive object;
• monitoring circuitry connected to the members of said array, said monitoring circuitry being operable to observe differential variation of signals as between members of said array;
• and
• a processor operable to compare signals sensed at said members of said array in response to electromagnetic signals emitted at said first frequency and at said second frequency.