CAPACITIVE NULL-MODE DISPLACEMENT MEASUREMENT TECHNOLOGY

摘要

Technique for sensing the absolute position of an object, in linear or rotary displacement, relative to a stationary object or the speed of displacement, is formed, in one embodiment, by two stationary elements and a moving element able to have a linear or rotary displacement when located between the stationary elements. The stationary elements have metallic coatings on their confronted sides to form eight capacitances whose value change when the moving element is displaced between them. Four pairs of sinusoidal waveforms are injected in the metallic tracks of one stationary element by the processing electronics whose amplitude is controlled to cancel each other in the metallic tracks of the confronted stationary element. The generation of the four pairs of sinusoidal waveforms occurs in a close loop that generates coarse and fine information of the position of the moving object. Such information is offered to a user as analog or digital.