Scientific, electrical, optical, monitoring and measuring instruments, namely, instruments for measuring the thickness of layers, in particular by eddy current, [ electromagnetic radiation, magnetic induction and/or coulometric methods, ] instruments for measuring thickness of coatings, alloy composition, material analysis, [ porosity, electrical conductivity, ferrite content, microhardness, ] phase angles, and other properties of coatings and layers; [ magneto-, opto-electronic data recordin...