A NOVEL LOW-COST CAPACITIVE-SENSOR INTERFACE

This paper describes the design of a new capacitive sensor interface, The interface is based on the use of a novel type of oscillator whose frequency is insensitive to low- and high-frequency interfering signal s by the application of a third order high-pass filter and special dit her techniques, The fully integrated 0.7 mu m CMOS circuit shows an in accuracy of less than 100 aF with respect to a 2 pF reference capacito r over a -30 degrees to +70 degrees C temperature range, The applied m easurement concept guarantees high stability, high accuracy and a negl igible influence of parasitic capacitances without the need for calibr ation.