How does test frequency affect the penetration depth of eddy currents?

Test frequency significantly influences the penetration depth of eddy currents in a material. As frequency decreases, the eddy currents are able to penetrate deeper into the conductive material. This phenomenon occurs due to the skin effect, where higher frequencies tend to confine the eddy currents closer to the surface of the conductor, resulting in reduced penetration depth. In contrast, lower frequencies facilitate greater depth penetration because the rise in the skin depth allows the currents to extend further into the material.

In this context, frequency directly determines the extent to which eddy currents can access underlying layers of the material being tested. Hence, understanding the relationship between frequency and penetration depth is crucial for optimizing testing parameters in Eddy Current Testing.