A method for characterizing a load on a data line includes the steps of: Applying at least three successive voltages to the data line. Ends of the core protrude from the casing for connection to a frame or other structure. The semiconductor membrane layer is initially formed from a substrate of standard thickness, and all but a thin surface layer of the substrate is then etched or polished away. The saddle closely straddles the plunger carrier, maintaining the alignment of the arcuate plunger with the arcuate plunger bore, for a plunger stroke without friction.