Abstract: In a method of scanning, with the aid of a sensor device, a yarn of a predetermined length which is intermittently withdrawn from a winding reservoir provided on the storage drum of a yarn feeding device for weaving machines, the yarn pulse acceptance for exclusively at least one first yarn pulse is changed at an increasing yarn speed and/or upon generation of at least one first or each winding signal to a yarn pulse acceptance for further faster yarn pulses and non-acceptance of interference pulses that are slower than the second yarn pulses. A yarn withdrawal sensor which is suited for said method is characterized in that a filtering device is provided with two different selective filtering modes that differ from each other by their acceptance of yarn pulses generated at different yarn withdrawal speeds, and that the filtering device is switchable at an increasing yarn withdrawal speed from a first filtering mode to at least one further filtering mode.

Abstract: An optoelectronic sensor device (S) for detecting a yarn passing through a scanning zone (3) comprises at least one light source (L, L'), at least one photoelectric receiver (R1, R2) which is responsive to light variations and which is connected to an evaluation circuit (C), and a slit aperture (A1, A1) arranged between the yarn and the receiver. In a weft-yarn measuring and storing device (F), the sensor device (S) forms a withdrawal sensor for the yarn which is withdrawn overhead from the storage body (B). According to the invention at least two receivers that are closely adjacent to each other are oriented towards the scanning zone, with the receiving surfaces (4, 5) of the receivers being each covered by an upstream slit aperture (A1, A2), except for a limited area. The slit apertures (A1, A2) are arranged relative to one another at an acute angle of not more than 90.degree..