Calculation and simulation of impedance diagrams of planar rectangular spiral coils for eddy current testing

The knowledge of analytical expressions for the electromagnetic (EM) fields produced by the coils used in eddy current testing is an important point in the development and application of these devices. In the present work, the second order vector potential formulation is used for the calculation of the fields produced by planar rectangular spiral coils of arbitrary number of turns and finite rectangular cross-section placed on a conducting half-space. Impedance plane diagrams are calculated for different frequencies, lift-off and half-space conductivity. Tests for conductivity assessment are also simulated. The theoretical results are compared with experimental measurements.