a system includes a capacitively - coupled touch sensor having a conductive first layer and a conductive second layer on a first insulative layer . the width of the second layer varies along an axis of the first layer . a first excitation signal is applied to one of the first and second layers and is capacitively coupled through a touch element to the other layer , producing a first signal that produces a second signal which is digitized . digitized peak values of the second signal are processed to compute a value for a touch element location . a conductive third layer can be placed on the opposite side of the first layer has width varying oppositely to the second layer . the first excitation signal is applied to the second layer and a non - overlapping second excitation signal is applied to the third layer . the resulting digitized peak values are processed to cancel errors due to variations .