Patent ID: 8593403

Claim:
A pointing stick device, comprising: a signal source element which comprises a plurality of strain gauges for sensing forces exerted onto a pointing stick and generating voltage signals; a voltage approaching element providing an incremental voltage for comparing with said voltage signals generated by said signal source element, wherein said voltage approaching element comprises a voltage division circuit providing a predetermined voltage to said incremental voltage according to said strain gauges of said signal source element, a first approaching unit lifting said incremental voltage close to said voltage signals such that said incremental voltage is lifted not to exceed said voltage signals, and a second approaching unit lifting said incremental voltage linearly, wherein said first approaching unit comprises a first current source, a first approaching capacitor, and a first switch for coarse approaching and for adjusting an error introduced by an inaccuracy of resistors, wherein said first approaching capacitor is connected with said first current source through said first switch, wherein when said first switch is closed in a predetermined period of time, said first approaching capacitor is charged to a predetermined voltage level, wherein said second approaching unit comprises a second current source, a second approaching capacitor, and a second switch, wherein said second approaching capacitor is connected with said second current source through said second switch, wherein when said second switch is closed, said second approaching capacitor is being charged while said incremental voltage is lifted linearly with a predetermined rate, wherein said first and second current sources are programmable to provide different values; and a signal process element comparing said voltage signals of said signal source element and said incremental voltage of said voltage approaching element, and counting the time for said incremental voltage to reach to a level related to said voltage signals for calculating said forces exerted onto said pointing stick.