1. An apparatus comprising: a plurality of capacitors each having a first electrode and a second electrode; charging circuitry coupled to the first electrodes; sensing circuitry coupled to the second electrodes, the sensing circuitry configured to detect changes in capacitance across the capacitors responsive to movement of an input object related to the apparatus; a low pass filter to filter an output of the sensing circuitry; an analog to digital converter connected to the output of the low pass filter; and interpolating circuitry to identify which one of the capacitors is nearest to the input object according to the detected capacitance changes.