In impedance diagrams, what effect does increasing the input frequency typically have on the eddy currents?

Increasing the input frequency generally leads to an increase in the eddy current response. This occurs because a higher frequency causes the electromagnetic field generated by the coil to change more rapidly, which in turn induces stronger eddy currents in the conductive material being tested. As frequency increases, the skin effect becomes more pronounced, leading to eddy currents being concentrated near the surface of the conductive material. This increase in eddy currents results in a stronger signal that can be detected by the testing equipment, enhancing the sensitivity of the Eddy Current Testing.

In the context of an impedance diagram, this means that as the frequency rises, the impedance due to the eddy currents increases, which shifts the response on the diagram. This is particularly important in NDT (Non-Destructive Testing) applications where variations in conductivity or surface conditions can be detected based on the changes in the impedance readings at different frequencies.

Thus, the reason why increasing the frequency leads to an increased eddy current response is tied to both the nature of electromagnetic induction and how eddy currents behave in conductive materials.