1. A sensing capacitor consisting essentially of: a portable, unitary capacitive structure that includes; an insulator body of a dielectric material; first elongated electrode extending a distance into the insulator body with an input terminal end protruding from one end of the insulator body; and a second hollow electrode closed at one end extending a distance into an opposite end of the insulator body, the closed end forming an output terminal protruding from the end of the insulator body opposite the input terminal, the internal portion of the second electrode surrounding and partially enclosing a section of the first electrode opposite the input terminal for an incomplete overlap and a physical separation between the first and the second electrodes, and wherein said insulator body is configured to allow external electrical connections to be made to the input terminal end and the output terminal.