Application challenges of capacitive sensors with floating targets

Capacitive sensors can detect movement of their electrodes or of changes in their dielectric. This paper discusses the challenges of detecting floating targets, in which the moving target is not connected by wire. It is shown that the constraints of such sensors are related to physical effects related to circumstances in the neighborhood of the sensor, which are application dependent. This is shown for three applications of capacitive sensors: (a) Presence detection of floating targets, such as human, animals and objects, where it is difficult to get a reliable result, (b) Detection of a conductive or dielectric floating rotor in an angular encoder, and (c) Detection of displacements, in the sub-nanometer range, over a small range.