| 摘要 |
<p>The yarn passes around a driven pulley and in slipping exerts a braking force so that the actual rotational speed of the pulley is proportional to the slip. A perforated disc is connected to the pulley shaft and a light source and photodetector are respectively arranged on opposite sides of the disc. The frequency of the light impulses received by the detector via. the perforations corresponds to the rotational speed of the disc and therefore the pulley. The device is simple and accurate.</p> |
