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Electromagnetic Testing

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Q.8.8 The region of intense electromagnetic interaction at the interface<br />

between an alternating current coil's outside diameter surface and a tube<br />

wall's inside diameter surface is called the:<br />

A. direct couple zone.<br />

B. fresnel zone.<br />

C. near field zone.<br />

D. Both A and C.<br />

E. None of the above.<br />

Q.8.9 The operating frequencies that are selected to perform remote field<br />

testing inspections are:<br />

A. usually higher than those used in conventional eddy current tests.<br />

B. usually lower than those used in conventional eddy current tests.<br />

C. identical to those used in conventional eddy current tests.<br />

D. about one half of those used in conventional eddy current tests.<br />

• Near Field (direct coupled) Zone - (0-1.5 tube diameters from the<br />

driver coil)<br />

• Transition Zone - (1.5-2 tube diameters from the driver coil)<br />

• Remote Field Zone - (2-3 tube diameters from the driver coil)<br />

Charlie Chong/ Fion Zhang

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