What does the term "lift-off" refer to in eddy current testing?

In eddy current testing, "lift-off" specifically refers to the distance between the test coil and the test surface being examined. This concept is crucial because lift-off affects the strength of the eddy currents generated and the resulting signal captured by the testing equipment. As the distance increases, the strength of the induced eddy currents decreases, which can lead to signal attenuation and potentially impact the effectiveness of the inspection.

Understanding lift-off is essential for accurate interpretation of test results, as variations in this distance can mask defects or lead to false calls regarding the presence of flaws. Therefore, maintaining a consistent lift-off is important for reliable measurements and assessments during eddy current testing.