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Electromagnetic Testing

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Hybrid Coils<br />

Hybrid coils may be defined as driver/pickup, through transmission, reflection<br />

or primary/secdndary coil assemblies. Hybrid coils may or may not be the<br />

same size and are not necessarily adjacent to each other. Figure 2.7 shows<br />

one possible hybrid coil arrangement. In the through transmission coil, the<br />

excitation coil is on one side of the test object and the sensing coil is on the<br />

other. The driver coil induces eddy currents and a secondary magnetic field in<br />

the test specimen. Any variation of these secondary events should be<br />

detected by the smaller probe coil on the opposite side of the thin plate.<br />

Charlie Chong/ Fion Zhang

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