Capacitive sensing devices can use single-ended sensing or differential sensing.
With single-ended sensing, capacitance is measured between the diaphragm and
a single capacitor plate in close proximity to the diaphragm. Differential sensing
can be used when there are capacitor plates on either side of, and in close proximity
to, the diaphragm (see Fig. 12.12a). In differential sensing the two capacitors
can be used to form two arms of an ac bridge or switch capacitor techniques