Fml. Vandergoes et Gcm. Meijer, A NOVEL LOW-COST CAPACITIVE-SENSOR INTERFACE, IEEE transactions on instrumentation and measurement, 45(2), 1996, pp. 536-540
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.