4 - Capacitive sensors for displacement measurement in the subnanometer range

Abstract

The main challenge in designing an interface circuit for capacitive displacement sensors with subnanometer resolution is the large offset capacitance of the sensor. This offset capacitance results from the relatively large distance between the sensor electrodes, compared with the displacement range to be measured. Of the different methods, which interface capacitive sensors, a charge-balancing technique is used here to demonstrate a power-efficient way to remove the offset, while maintaining high resolution and a short conversion time. To demonstrate this technique, the design of an oversampling capacitance-to-digital converter based on a third-order sigma/delta modulator is presented.