Patent ID: 6998856

Claim:
A position sensing device comprising: an oscillator that generates an oscillating injection signal for coupling to a first body part of a human body, the injection signal generating an electric field about a second body part; a first input operable to receive a first position signal from a first position sensing electrode that senses the strength of the electric field from the second body part in a non-contacting manner; a second input operable to receive a second position signal from a second position sensing electrode that senses the strength of the electric field from the second body part in a non-contacting manner, the first and second position sensing electrodes being spaced from each other; a first amplifier coupled to the first input and operable to amplify the first position signal by a first amplification factor; a second amplifier coupled to the second input and operable to amplify the second position signal by a second amplification factor, the first and second amplification factors being dependent on the sensitivity of the first and second sensing electrodes in sensing the position of the second body part in one direction relative to the other direction; and a difference circuit connected to the first and second amplifiers and operable to determine the difference between the first and second amplified signals, the output of the difference circuit representing a position of the second body part relative to the first and second electrodes.