How do you track pads on laptops know that human fingers are touching it?
Touchpads operate in one of a few different ways, all of which entail sensing the capacitance of a finger, or the capacitance between sensors. This is why they will not sense the tip of a pencil or other similar implement. Gloved fingers may be problematic (such as in a cleanroom environment) but can sometimes work. Moist, sweaty, or calloused fingers can be problematic for those touchpads that rely on measuring the capacitance between the sensors. 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 and crossing each other at right angles to form a grid. A high frequency signal is applied sequentially between pairs in this two-dimensional grid array. The current that passes between the nodes is proportional to the capacitance. When a virtual ground, such as a finger, is placed over one of the intersections between the conductive layer some of the electri
