Capacitive position sensors prevail in small battery-poweredinstruments. They “read” a scale (consisting of a row offloating electrodes) with a row of driver electrodes and a pickupelectrode, shielded so that mutual coupling may only occur via thescale. The novel sensor described here has only one row of identicalmultipurpose electrodes, acting in turn as driver, pickup and shield. Atheoretical model for inter-electrode capacitance optimizes sensorgeometry at a size suitable for integrating the complete sensor on a 7.5by 3.9 mm die. Drive and control signals scan the electrodes and theposition-tracking phase of the filtered pickup signal is digitallyfiltered on-chip. Measurements made with a 1.016 mm scale pitch and asensor to scale gap of 0.2 mm are linear to 0.002 mm within one pitch
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