Dual eddy current probe for detecting geometrical differences especially as related to threaded apertures and studs

A method for inspecting contours formed along a predetermined region of a surface on a workpiece formed of electrically conductive material using eddy current comprising the steps of:

• moving a probe having a longitudinal axis along a path of travel with respect to the predetermined region to be inspected on the workpiece, the path of travel being defined to include a testing portion of the path extending in a direction substantially coaxial with the longitudinal axis of the probe;
• electrically exciting at least two coils spaced longitudinally from one another and supported by the probe with a predetermined frequency and amplitude during movement of the probe along the path of travel;
• and
• measuring the excitation voltage of each coil as eddy currents are induced in the electrically conductive material of the workpiece by the coils supported on the probe moving along the path of travel with respect to the workpiece.

An apparatus for inspecting contours formed along a predetermined region of a surface on a workpiece formed of electrically conductive material using eddy current comprising:

• a probe having a longitudinal axis, the probe movable along a path of travel with respect to the predetermined region to be inspected on the work piece, the predetermined region including at least one thread;
• at least two coils spaced longitudinally from one another and supported by the probe to be electrically excited with a predetermined frequency an amplitude during movement of the probe along the path of travel;
• and
• means for measuring the excitation voltage of each coil as eddy currents are induced in the electrically conducted material of the work piece by the coil supported on the probe moving along the path of travel with respect to the work piece.

An apparatus for inspecting contours formed along a predetermined region of a surface on a work piece formed of electrically conductive material using eddy current comprising:

• a probe having a longitudinal axis, the probe movable along a path of travel with respect to the predetermined region to be inspected on the work piece, the predetermined region to be inspected remaining substantially stationary with respect to the movement of the probe;
• at least two coils spaced longitudinally from one another and supported by the probe to be electrically excited with a predetermined frequency and amplitude during movement of the probe along the path of travel;
• and
• means for measuring the excitation voltage of each coil as eddy currents are induced in the electrically conducted material of the work piece by the coils supported on the probe moving along the path of travel with respect to the work piece.