What does the term "lift-off" refer to in the context of Eddy Current Testing?

In the context of Eddy Current Testing, the term "lift-off" refers to the distance between the probe and the surface being tested. Lift-off is a critical factor because it directly influences the eddy currents generated and detected during the testing process. When the probe is positioned further away from the surface, the amplitude of the test signal diminishes due to the reduced interaction between the induced currents and the conductive material beneath.

Understanding the effect of lift-off is essential for accurate testing, as variations in this distance can affect the sensitivity and reliability of the measurements. It helps in assessing the condition of materials by enabling technicians to distinguish between genuine signals caused by flaws and those influenced by external factors, such as separation distance or surface conditions.

This concept underscores the importance of maintaining a proper distance during testing to ensure that the readings reflect the true characteristics of the material being examined instead of being distorted by the lift-off distance.