Which of the following factors can affect the sensitivity of eddy current testing?

The sensitivity of eddy current testing is influenced by multiple factors, and it's essential to consider all of them for effective testing.

The frequency of the testing plays a crucial role because it affects the skin depth, which is the depth at which eddy currents are concentrated in a conductor. Higher frequencies result in shallower penetration of eddy currents and can enhance sensitivity to surface defects, while lower frequencies allow for deeper penetration, making it more sensitive to sub-surface flaws.

The shape and size of the test probe also significantly impact sensitivity. A probe that is too large may not detect small cracks or defects, while a well-designed probe can interact optimally with the electric field created by the eddy currents, improving the ability to identify anomalies in the material.

Additionally, the material properties of the test specimen, such as conductivity, permeability, and thickness, can greatly affect the eddy current response. Different materials will respond differently to eddy currents, directly influencing the results obtained during testing.

Taking these factors into account, it becomes clear that all of them collectively influence the sensitivity of eddy current testing, making "all of the above" the correct choice. This holistic understanding is vital for ensuring accurate and reliable inspection outcomes.