Process and device for optical detection of impurities, especially fibres, in advancing yarn

摘要

Yarn impurities are detectable by a method and device wherein a first diameter-dependent signal is obtained in a first measurement of a linearly traveling yarn, the intensity of the light for a second measurement is set as a function of the first signal to compensate for the effect of the yarn diameter on the light reflected by the yarn and then the second electrical signal can be directly evaluated for detecting yarn impurities. The invention improves the detection of impurities, for example in connection with spinning and bobbin winding machines.