Abstract: A sensing system for a keyboard. Each key sensor comprises passive and active resonant circuits. The passive resonant circuit has a resonant frequency and the active resonant circuit excites the passive resonant circuit at the resonant frequency. A sensor driver drives the active resonant circuit with an RF drive signal, a multiplexing system multiplexes the drive signal such that simultaneously driven key sensors are separated by at least (k?1) keys, and a detector detects a level of RF signal from a driven key sensor for sensing a position and/or velocity of a key.

Abstract: An operation detection device for a key operation of a keyboard device includes a conductive unit configured to be disposed on each of keys, a substrate configured to be disposed facing each of the keys in a pressing direction of the keys. The substrate is provided with a sensor including at least first and second coils, the sensor being configured to be disposed spaced from one key so that at least one of the first or second coil outputs a signal corresponding to a distance between the one key and the respective sensor. The operation detection device includes a detection unit configured to detect a displacement of the one key in at least one of a yaw direction or a roll direction based on signals output from the first and second coils during a key pressing stroke of the one key.