There are two principal means by which touchpads work. In the ‘matrix approach’, a series of conductors are arranged in an array of parallel lines in two layers, separated by an insulator. The conductors in these layers are oriented orthogonally to one another. A high frequency signal is applied sequentially between pairs in the two-dimensional matrix created by the conductor array. The current that passes between the nodes is proportional to the capacitance. When a virtual ground, such as the finger, is placed over one of the intersections between the conductive layer some of the electrical field lines are shunted to this ground point, resulting in a change in the apparent capacitance at that location. This method received U.S. Patent 5,305,017 awarded to George Gerpheide in April 1994. The ‘capacitive shunt method’, described well in an application note by Analog Devices[4], senses the change in capacitance between a transmitter and receiver that are on opposite sides of the sensor. The transmitter creates an electric field which oscillates at 200-300 kHz. If a ground point, such as the finger, is placed between the transmitter and receiver, some of the field lines are shunted away, decreasing the apparent capacitance.
snap ut nog steeds niet

en er wordt niet uitgelegd waarom het alleen reageert op een vinger.