The ElektroPhysik 80-640-0101 MikroTest FM 6 Banana Gauge, Automatic Coating Thickness Gauge MIK/010120, 0 - 40 mils is also able to provide you with precise measurements in tubes and on round parts due to the automatic operation. The measurement of the coating thickness is based on magnetic attraction. The attractive force is related to the distance between a permanent magnet and a steel substrate. This distance represents the thickness of the coating under measure. The magnet is lifted from the surface by means of a spring connected to the magnet arm. The force needed to lift the magnet is directly related to the angle of rotation of the torsion spring. This measuring principle is also especially suited for electroplated nickel on copper, aluminum and other non-ferrous metals. This measurement principle ensures fully automatic measurement where no power supply or calibration is required.