Used to examine the even circumstance of the lap 1m, 1/2m, 1/3m length parts. Meanwhile it tests the lap actual length, calculates the extensibility of the laps.

• 用于试验棉卷1m、1/2m、1/3m长度片断的均匀情况，同时测试棉卷的实际长度，核算棉卷的伸长率。