In eddy current testing, which variable is classified as a high frequency variable?

In eddy current testing, small discontinuities are classified as high frequency variables due to their ability to create significant alterations in the electromagnetic field at higher frequencies. The eddy current testing technique relies on induced currents that flow in response to alternating magnetic fields. Small defects or discontinuities, such as cracks or laps, generate more pronounced changes in these currents at higher frequencies. These changes create distinct impedances that are easier to detect, making high frequency testing effective for identifying minor flaws that may go unnoticed with lower frequency currents.

While conductivity changes, diameter changes, and wall thickness variations can affect the overall response of the eddy currents, they are typically addressed with lower frequency settings and are more indicative of broader material properties rather than the small-scale defects that high frequencies are specifically designed to identify. Therefore, the focus on small discontinuities highlights the sensitivity of high frequency eddy current testing in detecting subtle defects within conductive materials.