Pie Gauge is used to verify the direction of magnetic flux on a surface. It is produced from eight ferrous segments, braised into a single piece, providing a star pattern of non- ferrous discontinuities.
Usually pie gauge is used with dry powders for yoke inspection and held at any angle and will generate indications perpendicular to the direction of the magnetic flux. Indications perpendicular to the magnetic flux will be stronger and well defined than the indications at an angles. You will not see any indications parallel to (in line with) the magnetic flux. Kindly note that pie gauge does not indicate magnetic field strength.