Flexible coil assembly for reflectance-mode nondestructive eddy-current examination

A method for non-destructive eddy-current examination of a conductive member, comprising the steps of:

• placing an assembly of driver coils and of detector coils in close physical juxtaposition to the member to be examined, said assembly comprising:
• a planar substrate;
• a first array of driver coils disposed on one side of said substrate, said first array comprising a plurality of parallel columns of coils connected in series to one another, each of said parallel columns of coils comprising parallel outgoing and return conductors, said outgoing and return conductors each being formed to comprise a number of series-connected coils, inner ends of said conductors being connected to means for controllably connecting said columns to a source of excitation energy, and outer ends of said outgoing and return conductors being connected to one another. whereby equal and opposite currents flow in the parallel conductors of each column;
• and
• a second array of detector coils disposed on the opposite side of said flexible substrate, said second array comprising a plurality of parallel rows of coils connected in series to one another, said rows extending in a direction other than parallel to said columns, each of said parallel rows of coils comprising parallel outgoing and return conductors, each of said conductors being formed to comprise a number of series-connected coils, inner ends of said conductors being connected to means for controllably connecting said rows to means for processing induced voltage signals detected by one or more of the coils of the corresponding row and outer ends of said conductors being connected to one another, whereby equal and opposite currents flow in the conductors of each column;
• sequentially connecting a source of excitation energy to the columns of coils of the first array;
• sequentially detecting and measuring the induced voltage signals in the rows of coils of the second array;
• and
• analyzing variations in the signals detected by the second array of coils to locate discontinuities in the member to be examined.

A system for eddy-current nondestructive examination of conductive members, comprising:

• a coil assembly, comprising:
• a planar substrate;
• a first array of driver coils disposed on one side of said substrate, said first array comprising a plurality of parallel columns of pairs of coils connected in series to one another, the coils of each column being provided as two parallel series-connected arrays, the arrays being connected to one another at a first end of each, and being connected to means for controllably connecting said columns to a source of excitation energy at their second ends;
• and
• a second array of detector coils disposed on the opposite side of said substrate, said second array comprising a plurality of parallel rows of coils connected in series to one another, said rows extending in a direction other than parallel to said columns, the coils of each column being provided as two parallel series-connected arrays, the arrays being connected to one another at a first end of each, and being connected to means for controllably connecting said rows to means for processing signals detected by one or more of the coils of the corresponding row;
• a source of excitation energy at a predetermined frequency;
• first multiplexing means for applying said energy in sequence to the plurality of columns of driver coils comprised by the flexible coil assembly;
• second multiplexing means for sequentially receiving and storing induced voltage signals detected by the plurality of rows of detector coils also comprised by said flexible coil assembly;
• and
• means for comparing the signals detected by the rows of detector coils and for identifying variations therein, and for determining the row and column of coils with respect to which the signals exhibiting the variations were recorded.

A flexible coil assembly for non-destructive eddy-current examination of electrically conductive members, comprising:

• a flexible planar substrate;
• a first array of driver coils disposed on one side of said flexible substrate, said first array comprising a plurality of first groups of coils connected in series to one another, each of said first groups being connected to means for controllably connecting said first groups to a source of excitation energy;
• and
• a second array of detector coils disposed on the opposite side of said flexible substrate, said second array comprising a second plurality of second groups of coils connected in series to one another, each of said second groups being connected to means for controllably connecting said second groups to means for processing signals detected by one or more of the coils of the corresponding group wherein each of the coils of said first and second groups of coils comprises a first and a second half-coil, the first half-coils being connected in series to the second half-coils.