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Electromagnetic Testing

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%IACS & Resistivity ρ (rho) in micro-ohm-centimeter<br />

■<br />

■<br />

%IACS = 172.41 / ρ micro-ohm-centimeter (μΩ∙cm)<br />

ρ micro-ohm-centimeter = 172.41 / %IACS<br />

These numerical values will be necessary when additional calculations are<br />

needed to determine issues of frequency choice, depth of penetration and I or<br />

phase spread to meet specific inspection criteria. As the test coil is influenced<br />

by different conductivities, its impedance varies inversely to conductivity. A<br />

higher conductivity causes the test coil to have a lower impedance value.<br />

Figure 4.1 illustrates this concept.<br />

Charlie Chong/ Fion Zhang

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