Abstract: A yarn measuring instrument having a rotatably mounted operative element whose rotation in response to frictional engagement thereof by travelling yarn cooperates with electronic circuit means to measure a plurality of characteristics of the travelling yarn is provided with means for capturing the travelling yarn and placing it in frictional engagement with the operative element. The yarn capturing means includes an arm which has a free end provided with yarn retaining means. The arm is mounted within the instrument for movement between a projected position thereof in which the yarn retaining means extends outwardly of the instrument and a retracted position thereof in which the yarn retaining means extends inwardly of the instrument, whereby travelling yarn captured in the retaining means when the arm is in its projected position automatically frictionally engages the operative element when the arm is moved to its retracted position.