Patent ID: 7800589

Claim:
A touchscreen position sensor comprising (a) a touch area having generally relatively low conductivity; (b) a relatively high conductivity border defining a perimeter on the touch area; (c) a grid of intermediate conductivity defining cells of relatively low conductivity within the high conductivity perimeter of the touch area, the relatively high conductivity border having a conductivity at least ten times greater than the conductivity of the relatively low conductivity touch area and the grid of intermediate conductivity having a conductivity at least four times greater than the relatively low conductivity touch area; (d) a set of electrodes attached to the high conductivity perimeter and connected to an electrical power source; (e) an electric circuit that measures the potential of a selected point on the touch area when brought in proximity thereto; (f) a controller that sequentially switches electrical power from the power source to a first group of the electrodes thereby establishing a first electrical potential distribution on the touch area, and then to a second group of said electrodes thereby establishing a second electrical potential distribution on the touch area; and (g) a controller that processes sets of potential measurements of said first and second electrical potential distributions from the electric circuit to determine the location of the selected point, wherein the controller may select subsets of a first set of cells to poll a subset of the cells.