Lift-off effect
The distance between the probe and the surface affects the electrical signal in eddy current testing. It must be compensated for accurate results.
Physical-Chemical Mechanism of Action
The lift-off is the distance between the probe and the metal surface. This distance affects the electric field generated by the probe, causing distortions in the measured signal.
Metallurgical Relevance & Risks in Welding
An inaccurate lift-off can lead to false results in eddy current testing. This can cause over- or under-evaluation of surface flaws, thus leading to errors in the quality control process.
Workshop Practice & Action Guidelines
To compensate for lift-off, the compensation circuits must be set correctly. This is done by entering the actual distance between probe and surface into the test instrument. The recommendation is to always use a fixed lift-off of 1 to 2 mm to achieve consistent results.