Patent ID: 8013600

Claim:
A battery-powered eddy current sensor for inspecting surface and sub-surface faults of a structure, said apparatus comprising: a primary planar eddy current coil; a secondary planar eddy current coil; a direct digital synthesizer and digital-to-analog converter that generate output signals for provision to the primary planar eddy current coil; an analog-to-digital converter that receives response signals from the secondary planar eddy current coil and digitizes the response signals to generate input signals, wherein said analog-to-digital converter, said digital-to-analog converter, and said direct digital synthesizer are synchronized; circuitry for calculating a voltage ratio and phase shift between the input and output signals; wherein said circuitry comprises the primary planar eddy current coil, the secondary planar eddy current coil, and a bridge circuit that is configured to measure a differential impedance change between the primary and secondary planar eddy current coils; and a battery that provides electrical power to the direct digital synthesizer, the digital-to-analog converter, the analog-to-digital converter, and the circuitry for calculating the voltage ratio and phase shift between the input and output signals.