Inductive measurement of metallic cylindrical shells

The thickness of thin cylindrical copper shells of radius
a
and thickness
D(D/a < 0.15)
were measured by means of an inductive measurement. The samples were obtained by chemical reduction of thick copper pipes. The conductivity of the cylinders was measured by a standard four-terminal technique. The agreement between the value of thickness measured mechanically and the value obtained from inductive measurement is of the order of ±2 percent. Thicker brass shells were measured and these results compared with theory. The extension of the inductive measurement to cylindrical shells covering cylinders with a finite conductivity is also discussed.