The number of untwisting revolutions per unit length of yarn.
Second, Detwisting and twisting method: for the thinner yarn in the traditional spinning of staple fiber, use detwisting and reverse twisting to make the yarn stretch and then shrink back to the original length, and use half of the added number of revolutions to do this. Segments of yarn grab the number. Recently, the secondary untwisting and twisting method, the three untwisting and twisting method and the four untwisting and twisting method have been developed. The purpose is to eliminate the structure change when the fiber strands are reverse twisted change. But it may also cause changes in the yarn structure and make the test results inaccurate.
Third, Reflective method: irradiate the yarn with a parallel beam, measure the angle of the peak deflection of the reflected light, and calculate the twist by accounting for the helix angle of the surface layer of the twisted yarn. For the quality of new yarns such as rotor spinning, electrostatic spinning, air-jet spinning, siro spinning, and self-twisting spinning, due to the different structures, especially the different yarn sheath cores, it is necessary to try to test them separately in different layers. Develop different testing methods