The accurate measurement of a micromechanical force using force-sensitive capacitances

Abstract

A sensor for the precise and accurate measurement of micro-mechanical forces is presented. The sensor is used to detect a tactile image and has capacitive force sensing elements which are detected by charge readout. The mechanical performance of the force sensor is evaluated and verified with experiments. The force-to-deflection and deflection measurements have been separated in order to result in a sensor structure in which the response is linear with force and little affected by fringe fields. The sensor is 0.25 mm/sup 2/ in size, it has a force range of 0.25 mN and a capacitance of 2 pF. The amplifier detects capacitance changes of 15 fF with a maximum non-linearity of 0.01% over the 1.25-2.5 pF range.<>