The CH-L length tester chooses thehigh-precision laser (KEYENCE 7000 Series) and precision pneumatic slideas the core components. The sample centering clamping device is used to ensure that the sample and the length of the laser head measuring grating are parallel, and the step motor drives the sample to rotate 360°.The laser controller collects the length measurement data of2400 times in one second to calculates the average of the length.