Apparatus for gauging the shape of a conducting surface

Abstract

An apparatus for gauging the shape of a specimen conducting surface or load distribution between normally mateable specimen conducting surfaces. A capacitance pad which is insertable between the specimen surface in question and a reference surface of known shape or normally mateable surfaces has multiple electrodes sandwiched between dielectric plates which are, during operation, situated adjacent the reference and specimen surfaces. The electrodes in the capacitance pad may be individually energized and selectively connected to a capacitance measuring circuit. Capacitance between the reference and specimen surfaces or between the normally mateable specimen surfaces changes the frequency of the measuring circuit when selected capacitance pad electrodes are connected to that circuit. The measuring circuitry counts the pulses emitted by an included oscillator within a selected period of time with the number of pulses being inversely proportional to the capacitance and, thus, also inversely proportional to the distance separating the surfaces. The distance between the surfaces is inversely related to the force or pressure on the sandwiched electrodes. By varying the period of pulse counting or dividing the number of pulses counted by selected numbers the specimen's surface shape or pressure distribution between mateable specimen surfaces may be displayed directly in the dimensional units desired.