Mountable eddy current sensor for in-situ remote detection of surface and sub-surface fatigue cracks
| DWPI Title: Portable battery-powered eddy current sensor apparatus for inspecting surface and sub-surface faults of e.g. aircraft, has battery providing power to synthesizer, converters, and circuitry for calculating voltage ratio and phase shift |
| Abstract: A wireless, integrated, mountable, portable, battery-operated, non-contact eddy current sensor that provides similar accuracy to 1970's laboratory scale equipment (e.g., a Hewlett-Packard GP4194A Impedance Analyzer) at a fraction of the size and cost. |
| Use: Portable battery-powered EC sensor apparatus for inspecting surface and sub-surface faults of a thick, multi-layer, conductive structure e.g. bridge, aircraft and building support. |
| Advantage: The apparatus provides deep penetration with a strong enough magnetic field to interrogate the structures, and avoids the lift-off effects of nonconductive layers/coatings to improve the strength of the eddy current (EC) field in the area of interest. The apparatus eliminates costly and potentially damaging disassembly, improves sensitivity by producing optimum placement of sensors with minimized human factors concerns in data acquisition, and decreases maintenance costs by eliminating time-consuming manual inspections. The apparatus quickly, routinely, and remotely monitors the integrity of the structure in service, and enables a reliable structural health monitoring system to automatically process data, assess structural condition, and signal the need for human intervention, so as to reduce the associated life-cycle costs. The apparatus detects incipient damage before catastrophic failures occur, allows operators to be even more vigilant with respect to flaw onset, thus initiating corrective repairs by early detection of structural damage, in cost effective manner by reducing the need for subsequent major repairs. |
| Novelty: The apparatus (10) has a digital-to-analog converter generating output signals for provision to a primary planar eddy current (EC) coil (1). An analog-to-digital converter receives response signals from a secondary planar EC coil (2) and digitizes the response signals to generate input signals. A bridge circuit measures a differential impedance change between the coils. A battery (22) provides electrical power to a direct digital synthesizer, the converters, and circuitry for calculating a voltage ratio and phase shift between the input and the output signals. |
| Filed: 5/12/2008 |
| Application Number: US2008119009A |
| Tech ID: SD 10741.1 |
| This invention was made with Government support under Contract No. DE-NA0003525 awarded by the United States Department of Energy/National Nuclear Security Administration. The Government has certain rights in the invention. |
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