The pie gauge is a disk of highly permeable material divided into eight sections by non-ferromagnetic material. The joining’s of section act as artificial defects that radiate out in different directions from the centre. The sections are furnace brazed and copper plated. The advantages of the pie gauge are that it is easy to use, and it can be used indefinitely without deterioration.

Usually, pie gauge is used with dry magnetic powder for detection of magnetic flux intensity. It is also used with wet fluorescent as well as visible magnetic particles. The pie gauge shows perpendicular and 45° indication to the produced magnetic flux direction. The pie gauge should be demagnetized between readings and cleaned regularly to avoid residual of magnetism. It is manufactured in compliance to ASTM E709 & E1444 standards.