When using eddy current testing with a frequency discriminating circuit, which variable is classified as high-frequency?

When using eddy current testing with a frequency discriminating circuit, small discontinuities are classified as high-frequency variables because they create fluctuating electromagnetic fields that respond more readily to higher frequencies. Eddy currents are induced in conductive materials by alternating magnetic fields, and the size of the discontinuity (like cracks or small voids) will influence how the eddy currents behave.

High-frequency signals are particularly sensitive to small changes in the structure of the material, which can accentuate the response to small discontinuities. For instance, a small crack will disrupt the flow of eddy currents at higher frequencies, making it easier to detect.

In contrast, larger features, such as diameter changes or variations in wall thickness, tend to have a more diluted effect on the eddy current response, making them more detectable with lower frequencies. Conductivity changes can also interact with eddy currents but are generally not categorized under high-frequency indicators in this context. Thus, small discontinuities are the critical factor when classifying variables as high-frequency in eddy current testing applications.