Capacitance sensing
Provided by the ASK Keyboard Dictionary
Also known as: capacitive sensing, capsense
Capacitance sensing (or simply "capsense") is a form of keyswitch sensing that relies on the principle that any two objects can be a capacitor and that the capacitance they can both hold together changes as one part is moved closer or away from the other. This can be used as a rudimentary distance measurement, which in turn can be used to tell if a given keyswitch is pressed by comparing the measurement against a desired threshold. Capacitive keyswitches are known to have a long lifetime compared to ohmic designs and have an inherent n-key rollover (provided the keyboard-to-host interface also supports NKRO). Keyswitches that utilise this include IBM beam spring, IBM capacitive buckling spring, Topre (specifically electrostatic capacitive (EC) sensing), and numerous foam and foil keyswitches. Keyboards that make use of capsense are generically known as "capacitive keyboards" and are generally more expensive to make and buy than ohmic keyboards.
