Capacitive sensing device

Abstract

A capacitive sensing device for detecting the presence of conducting and nonconducting objects with the distance between sensing tip and object remaining nearly constant regardless of their size or mass is disclosed. The device is particularly useful with the camera optical probe of an aircraft simulator for training pilots, and is mounted on the camera probe such that it generates a capacitance at its output which varies with the distance between the camera probe and objects on a terrain model board as the probe travels about the model board. Thus, if the optical probe approaches too close to an object, (especially an object outside the field of view of the pilot trainee) it generates a control signal to prevent the optical probe from crashing into such an object. The probe which can sense both nonmetallic and metallic objects comprises a capacitive sensing probe for sensing metallic objects which is of standard design in combination with a toroidal-shaped metallic member positioned around the standard probe at the sensing end. The capacitance of the toroidal-shaped member with respect to a target object, (either metallic or nonmetallic) is tuned to be substantially equal to the capacitance of the standard probe with respect to the same target object when the combination probe and toroidal members are at a selected distance from the target object.