Eddy Current Testing

In longitudinal wave inspection of the parent metal adjacent to a weld, minimum sensitivity is usually set such that

It is 6 dB over the 80% FSH level for the appropriate side-drilled hole.

It is 20 dB over the 80% FSH level for the appropriate side-drilled hole.

The backwall echo is 100% FSH in the absence of defects like crater cracks.

None of the above.