The capacitance of the sensor pad is measured periodically.
the sensor electrode, is connected to a measurement circuit.
The corresponding 2nd plate is represented by the environment of the sensor electrode (to form a parasitic capacitor C0) and another conductive object, like a human finger for example (to form touch capacitor CT). The electrode of a touch sensor represents one plate of such a capacitor. Capacitance sensors detect a change in capacitance when something or someone approaches or touches the sensor.