How does a Coating Thickness Gauge work?
Dry film thickness can be measured on either magnetic steel surfaces or non-magnetic metal surfaces such as stainless steel or aluminium using a digital coating thickness gauge. The principle of electromagnetic induction is used for non-magnetic coatings on magnetic substrates such as steel. The eddy current principle is used for non-conductive coatings on non-ferrous metals substrates.
Permanent Magnet Coating Thickness Gauges
A permanent magnet is mounted on a balanced arm and the force required to pull this magnet from the surface of the coating is a measure of the thickness of the coating. Force is applied through a helical spring attached to the balanced arm at one end and to a scale wheel at the other. As the scale wheel is turned the force is progressively increased until the magnet lifts from the surface. The scale is drawn in thickness units rather than force and the thickness of the coating can be read against a pointer on the case of the instrument.