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Electromagnetic Testing - Eddy Current Testing Applications Chapter 5 & 6

Eddy Current Chapter 5 and 6

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5.1.5.6 Frequency selection<br />

The frequency used for general conductivity measurement is 60 kHz,<br />

however where the ability to detect very small changes in conductivity is<br />

required, the frequency should be optimized, so that the change in coil<br />

impedance for a small change in conductivity is the greatest. If lift-off<br />

compensation is important because of a rough surface or a non-conducting<br />

coating, the lift-off signal should be as close as possible to 90° from the<br />

conductivity signal for change in conductivity, because signals are more<br />

easily suppressed if they are at 90° to the signal of interest.<br />

Keywords:<br />

lift-off compensation<br />

Optimized<br />

Charlie Chong/ Fion Zhang

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