Abstract: A mask for precisely defining the area of a thin metal layer on a substrate to be deplated during measurement of the thickness of the thin metal layer utilizing a coulometric technique. The mask having an adhesive on one side for securing the mask to the thin metal layer and for preventing the leakage of electrolyte between the mask and the thin metal layer.

Abstract: A beta backscatter type of measuring instrument including a workpiece positioning system to permit precise prepositioning of the workpiece surface to be subjected to radiation preparatory to moving the radiation source into operative proximity therewith.

Abstract: An improved backscatter instrument for the nondestructive measurement of coatings on a substrate. A memory having selectable memory areas, each area having stored intelligence available which is determinative of the shape of a functional plot of coating thickness versus backscatter counts per minute unique for each particular combination of emitting isotope, substrate material, coating material and physical characteristics of the measuring instrument. A memory selector switch connects a selected area of memory to a microprocessor operating under program control whereby the microprocessor reads the intelligence stored at the selected area and converts the backscattered count of the coating being measured into indicia of coating thickness.