How do you view an MFL signal? This question isn't as easy as it sounds. Flux leakage is a vector field - that is, it has both magnitude and direction at all points in space.

To make interpretation of MFL signals easier, we ordinarily talk about a plane of measurements through space, and we consider only one component of the vector field. That way, each point on the two-dimensional plane has one magnitude associated with it.

On the right are two sets of data. Each shows the same information: the magnitude of a field as measured by sensors moving along the pipe wall. The top is a strip chart. This is the historic method used for viewing inspection logs. The bottom is a wireframe. It gives a better feel for the data, but it's harder to use for direct measurements. By the way, the axial (long) direction is horizontal in the plots, and the circumferential direction is up or into the screen.