Multi frequency eddy current test apparatus with intermediate frequency processing
AssigneeElectric Power Research Institute, Inc.
InventorsThomas J. Davis, Charles B. Perry
Life of this patent
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Abstract
An eddy current test apparatus and method in which multiple sequential test frequencies are employed. The voltage induced in a sensing coil at said test frequencies are multiplexed and frequency translated to provide a single frequency for processing. The apparatus employs a single channel to process the induced voltages.
Claims12
Eddy current test apparatus including inducing coil means adapted to be coupled to an object to be tested to induce eddy currents in said object which currents induce voltages in sensing coil means, said induced voltages containing certain phase and amplitude information;
- means for sequentially providing at least two test frequencies, one at a time, to said inducing coil means;
- means for receiving and converting the induced voltages in said sensing coil means by said induced eddy currents to an intermediate frequency having a fixed predetermined frequency value independent of the frequency value of each test frequency selected while preserving said phase and amplitude information of said induced voltages, said converting means including first and second choppers and means for driving said first and second choppers at IF.angle.0.degree. and at IF.angle.90.degree., respectively, where IF is the intermediate frequency;
- and
- means for sequentially processing said intermediate frequency to provide in-phase and quadrature components, A.sub.i B.sub.i for each of the test frequencies.
Eddy current test apparatus including inducing coil means adapted to be coupled to an object to be tested to induce eddy currents in said object which currents induce voltages in sensing coil means said induced voltages containing certain phase and amplitude information;
- means for sequentially providing at least one test frequency to said inducing coil means;
- means for receiving and converting the induced voltages in said sensing coil means by said induced eddy currents to an intermediate frequency having a predetermined fixed frequency value independent of the frequency value of the test frequency selected while preserving phase and amplitude information of said induced voltages, said converting means including first and second choppers and means for driving said first and second choppers at IF.angle.0.degree. and at IF.angle.90.degree., respectively, where IF is the intermediate frequency;
- and
- means for sequentially processing said intermediate frequency to provide in-phase and quadrature components, A.sub.i B.sub.i for each of the test frequencies.
Dependencies are inferred from the claim text.