Abstract: A connector of electromagnetically insulative material includes a shaft section on a drive shaft end and a matching probe section on an eddy current probe mating to the shaft section with face to face contact surfaces to prevent electromagnetic fields from propagating along the surfaces. The connector includes upper and lower portions with power line connecting pins and matching sockets in the upper portions of the sections and communication line connecting pins and matching sockets in the lower portions of the sections. The pins and sockets are fitted within electrically nonconductive inserts within probe and shaft section bores, the inserts having magnetic permeabilities less than those of the probe and shaft sections.

Abstract: An eddy current probe with a probe body having at least one eddy current coil is centered on a probe shaft by a pod with a plurality of replaceable centering feet which allows abraded centering feet to be replaced while the balance of the probe is retained and reused. Typically, the probe body is sandwiched between a pair of such centering pods. The replaceable pods comprise matching halves, divided longitudinally, that fit together over the shaft. Each of the centering pods is retained against the body probe by means of a retaining cap threaded on the probe shaft against the joined pod halves urging the pod against the probe body. The pod extends into an annular trepan in the probe body to secure the pods at that end. A face within the retaining cap normal to the shaft or slanted acutely toward the probe and overhanging the pod retains the pod in position around the shaft at the retaining cap end.

Abstract: A plurality of beads with matching transverse faces and longitudinal bores cooperate to form a bendable shaft with a duct therethrough, held in face-to-face contact with a plurality of elastic bands within the duct. Alternatively, the plurality of bands may comprise a single elastic inner tube. The elastic bands may also mutually overlap to provide redundancy in case a band should break.

Abstract: An eddy current probe shaft with probe and drive mechanism attached for measuring integrity of a bolt hole, particularly useful for aircraft bolt holes, includes a continuous helical coil manufactured integrally into a one-piece steel shaft providing flexure in the shaft enabling axial self-alignment even when the shaft is inserted obliquely into a bolt hole. The intact, integrated helical coil of flexible steel provides a constant length probe, effectively noncompressible and nonelongatable, flexible under external bias and with a spring constant sufficient to reliably return the shaft to a straight-axis rest position upon release of the external bias. An eddy current probe with a test coil in a probe head is attached at the shaft distal end for measuring cracks and similar structural anomalies in the bolt hole. A drive mechanism is attached at the shaft proximal end for rotating the shaft and probe in the bolt hole for a circumferential scan of the bolt hole interior surface.

Abstract: An Eddy Currest Tester for detecting defects in conductive materials employs phase rotation circuitry for eliminating the effects of lift-off signals from the reactive component of the output of an eddy current probe. An operator digitally selects a frequency which is input to the eddy current probe which is adjacent a test material. The signal output from the eddy current probe is amplified and demodulated into reactive and resistive components which are processed by phase rotation circuitry. The phase rotation circuitry is calibrated by applying a lift-off signal thereto while a phase adjust switch is on. When the phase adjust switch is on the reactive signal component is applied to a zero crossing detector which in conjunction with a flip flop controls the counting direction of an counter which addresses a sine-cosine table in a eraseable programable read only memory.