Wall thickness is measured by placing a small steel target ball on one side of the test piece and the magnetic probe on the opposite side. The Magna-Mike 8600 precisely measures the distance between the probe tip and the target, which corresponds to the thickness of the wall.
The principal advantage of the technique is that thickness measurements require only limited access to both sides of the test sample, permitting measurement of open containers without needing to cut or break them as would be the case for glass bottles.
The technique is widely used for measuring the wall thickness of blow moulded containers which have parts with complex shapes, relatively thin, flexible walls, and corners that are difficult to measure with mechanical gauges.
Image courtesy of Olympus