Mountable eddy current sensor for in-situ remote detection of surface and sub-surface fatigue cracks

A battery-powered eddy current sensor apparatus 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 and the secondary planar eddy current coil;
• 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, wherein the primary planar eddy current coil, the secondary planar eddy current coil, the direct digital synthesizer, the digital-to-analog converter, the analog-to-digital converter, and the circuitry are integrated on a common substrate.

A portable sensor apparatus configured for in-situ monitoring of surface and sub-surface faults of a structure, the sensor apparatus comprising:

• a primary planar eddy current coil that has a geometrical shape of one of U-shaped, V-shaped, or C-shaped;
• a secondary planar eddy current coil that has the geometrical shape of the 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, wherein the direct digital synthesizer is configured to generate the output signals such that the output signals have a range of frequencies;
• 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, and wherein the response signals are indicative of severity and depth of a flaw in the structure, and 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 and the secondary planar eddy current coil;
• 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.