A METHOD OF MEASURING FINGERTIP LOADING DURING KEYBOARD USE

A single keycap on a standard alphanumeric computer keyboard was instr umented with a piezoelectric load cell and the fingertip motion was re corded with a high-speed video motion analysis system. Contact force h istories between the fingertip and the keycap were recorded while four subjects typed a standard text for five minutes. Each keystroke force history is characterized by three distinct phases: (I) keyswitch comp ression, (II) finger impact and (III) fingertip pulp compression and r elease. Each keystroke force history contained two relative maxima, on e in phase II and one in phase III. The subject mean peak forces range d from 1.6 to 5.3 N and the subject mean peak fingertip velocities ran ged from 0.3 to 0.7 m/s. Motion analyses and force measurements sugges t a ballistic model of finger motion during typing.