Capacitive sensing devices can use single-ended sensing or differential sensing. Single-ended sensing capacitance is measured between two capacitor plates, as shownin Chapter 8, Figure 8.7. Differential sensing can be used when there is a capacitorplate on either side of, and in close proximity to, a central plate or diaphragm, as shown in Chapter 7, Figure 7.5(a). In differential sensing, the two capacitors (A and B) can be used to form two arms of an ac bridge, or switch capacitor techniques can be used. For single-ended sensing, a fixed reference capacitor (B) can be used with a variable capacitor (A). Capacitive sensing can use ac analog or digital measuring techniques.