A feeder head includes suction belts to sequentially feed top sheets from a stack of sheets (e.g., paper). Before the belts receive suction and drive power, a suction cup raises the top sheet at a location between the belts to produce a corrugated shape in the top sheet which induce separation of a second sheet that might be adhered to the top sheet. A double sheet detector includes a pair of rollers forming a nip through which a fed sheet passes, causing the rollers to separate. The amount of separation is transmitted to a transducer which generates a signal proportional to the sheet thickness. Signals from the transducer are frequently sensed and averaged, so that signal variations resulting from irregularities in the shape of the rollers are canceled out.