Coating Thickness Gauge The instrument adopts the magnetic and eddy current principle to measure in a non-destructive way Coating Thickness Gauge I. Measuring PrincipleThe instrument adopts the magnetic and eddy current principle to measure in a non-destructive way (1) Magnetic way (type F probe) measure the thickness of non-magnetic coatings on magnetic metallic base (e.g. zinc, aluminum, Cr. ...