A device for handling a substantially circular wafer is provided. The device includes an interior accessible through a plurality of entrances, and a plurality of sensors consisting of two sensors for each one of the plurality of entrances, each sensor capable of detecting a presence of the substantially circular wafer, at a predetermined location within the interior, wherein the plurality of sensors are arranged so that at least two of the plurality of sensors detect the wafer for any position of the wafer entirely within the interior, wherein a first one of the two sensors is positioned to detect the wafer when the wafer has passed entirely into the interior through one of the plurality of entrances, and a second one of the two sensors is positioned immediately outside a diameter of the wafer when the wafer has passed entirely into the interior through one of the plurality of entrances.