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Capacitive Touch Sensing Solutions Slide 14

This is a practical explanation of how this is done. Illustrated here is a controller with four sensors, or four copper pads, and each one of them is connected through four copper traces of different length. At the beginning, the intrinsic capacitance will be different because the channel with the sensor that is farther away will have a higher capacitance. As mentioned before, working with both external capacitors and the reference capacitance (which can be changed through a register), the user can equalize those capacitances to be as close to each other as possible and bring them within the actual dynamic range. By doing this, the objective of putting the system in a condition as balanced as possible is achieved, assuring that the controller will properly detect capacitance changes due to user touch.

PTM Published on: 2011-12-12