Capacitive displacement sensor

Abstract

A distance measuring system ( ) is provided with a capacitive sensor ( ), designed in the form of a differential capacitor ( ), for which the partial capacitors (C , C have capacitances that depend on the position to be determined. The system also includes a processing device ( ) for determining the desired distance that contains, for example, a sigma/delta demodulator. The partial capacitors (C , C ) are triggered periodically with binary signals, wherein the trigger signals from the one partial capacitor (C ) are transmitted with a phase offset to the signals from the other partial capacitor (C ). The processing device ( ) determines which trigger signals must be used for the evaluation. Within time windows that are synchronized with the edges of the trigger signals, a switch unit ( ) allows the associated receiving signals to pass through to the processing unit ( ) and blanks out all other signals. The distance measuring system ( ) makes it possible to have a low number of interpolation errors with high resolution and long interpolation periods. The distance measuring system ( ) can be expanded by adding two essentially independent, parallel-operating relative measuring systems to form an absolute distance measuring system, which determines the absolute position solely from the current measuring values. A nearly optional enlargement of the measuring range is possible by adding further relative measuring systems.