When testing small parts using an eddy current encircling coil, which test parameter is considered important?

In Eddy Current Testing (ET), particularly when using an encircling coil to assess small parts, all specified test parameters—length, thickness, and cross-sectional area of the test sample—are significant.

The length of the test sample is vital because it affects the overall magnetics and the penetration of eddy currents, influencing the sensitivity and accuracy of detection for defects. When a sample is longer than the coil, uniformity in testing may be disrupted as the eddy currents may not be established throughout the entire sample.

Thickness plays a crucial role because it determines how deeply the eddy currents can penetrate the material. In many materials, as thickness increases, eddy current flow is affected, which can lead to reduced sensitivity to detect surface or near-surface defects. Therefore, understanding the thickness allows the technician to adjust the frequency and gain settings appropriately to obtain accurate results.

Cross-sectional area impacts the overall resistance and impedance of the part being tested. Larger cross-sectional areas may result in stronger eddy currents, while smaller areas could lead to faster decay of the eddy current flow, both of which influence the signal detected by the testing equipment.

Given that each of these parameters affects the interactions of the eddy current within the material differently and can introduce