Super sensitive eddy-current electromagnetic probe system and method for inspecting anomalies in conducting plates

TL;DR: In this paper, an eddy-current probe is described, which includes an excitation coil unit, a magnetic detector within the probe, a signal-conditioning/preamplifier circuit, and a signal channel.

Abstract: Devices and methods for improved inspections of conducting structures of different shapes. An eddy-current probe includes an excitation coil unit, a magnetic detector within the probe, a signal-conditioning/preamplifier circuit within the probe, and a signal channel. The excitation coil unit is shielded on substantially all sides except an emission face that transmits an alternating magnetic signal to a conducting (e.g., metal) object, such that the metal object modifies the alternating magnetic signal. The magnetic detector within the probe is also shielded on substantially all sides except a reception face, such that the alternating magnetic signal as modified by the metal object is received into the shielded magnetic detector and converted into a first electrical signal. The signal-conditioning/preamplifier circuit within the probe is shielded on substantially all sides and provided with electrical power. The shielded preamplifier provides detection for very small signals, such as from magnetic probing of aircraft skin metals. Other embodiments include a traveling-wave excitation structure and a multiple-phase driving circuit, some of which include the shielded pre-amplifier, and others of which are not shielded. An eddy scope is described that provides a multiple-phase excitation signal to various different probes.