Dual coil probe for detecting geometric differences while stationary with respect to threaded apertures and fasteners or 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 to a static testing position substantially coaxial with the longitudinal axis of the probe with respect to the predetermined region to be inspected on the workpiece;
• electrically exciting at least two coils spaced longitudinally from one another and supported by the probe with a predetermined frequency and amplitude while stationary at the static testing position;
• 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 while stationary 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 to a static testing position stationary with respect to the predetermined region to be inspected on the workpiece, 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 while stationary at the static testing position;
• and
• means for measuring the excitation voltage of each coil as eddy currents are induced in the electrically conducted material of the workpiece by the coil supported on the probe while stationary 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 to a static testing position stationary with respect to the predetermined region to be inspected on the workpiece, the predetermined region to be inspected remaining substantially stationary with respect to the stationary static testing position of the probe during testing;
• at least two coils spaced longitudinally from one another and supported by the probe to be electrically excited with a predetermined frequency and amplitude while stationary at the static testing position;
• and
• means for measuring the excitation voltage of each coil as eddy currents are induced in the electrically conducted material of the workpiece by the coils supported on the probe while stationary with respect to the workpiece.