A weft feeder comprising weft sensors with movable magnetic elements that cooperate with respective detectors located outside the feeder drum; the detectors react with a signal, without contact, when the position of the corresponding weft sensor changes. Each detector in turn comprises an acquisition sensor capable of providing an analog signal, in terms of voltage, that can vary in a linear manner as the angular positions of the movable magnetic elements of the weft sensors vary. The acquisition sensors are operatively connected to a microprocessor for controlling the motor of the feeder, which is programmed to automatically set the values of the weft presence threshold and of the weft absence threshold and to filter the values of said signals.