What effect does increasing the distance of lift-off have on Eddy Current measurements?

Increasing the distance of lift-off in Eddy Current testing negatively impacts measurement sensitivity. This phenomenon occurs because the eddy currents generated in the conductive material being tested decrease in strength as the distance between the probe and the surface increases. When the probe is further away, the electromagnetic coupling between the probe and the material becomes weaker, resulting in a reduced ability to detect defects or variations in conductivity.

As lift-off increases, not only does the signal from the eddy currents diminish, but the influence of noise and other unwanted signals can also become more pronounced, leading to a lower signal-to-noise ratio. Consequently, the ability to differentiate between subtle changes in the material's properties decreases, making it more challenging to identify flaws or variations accurately.

Enhanced measurement sensitivity is critical for reliable defect detection, as it allows for finer details in the response to be discerned. Therefore, increasing the distance of lift-off is detrimental to the effectiveness of Eddy Current measurements, confirming that sensitivity is indeed decreased.