Abstract: A plurality of sensing coils are formed by spiral coil electrical conductor sections deposited on a flexible substrate which is formed into a cylindrical form about a central axis. The conductor sections are spaced apart by a distance equivalent to one-quarter of the circumferencial length of the cylindrical form, to define four separate coils spaced apart by 90 degrees. Coil sections are deposited in the register on opposite sides of the substrate and interconnected through the substrate. The coil pattern may be repeated in adjacent areas of the substrate to form a multi-layered coil when a number of turns of the substrate are wound around the central axis.