Cast iron surface plate placement or adjustment is not correct, which will directly affect the measurement accuracy, it should be adjusted and placed properly.
Before the test by changing the height of the three supporting points, adjust the cast iron plate to level, so that the plate load evenly distributed in the fulcrum. Large flat plate increase the support point need stable pad, can not damage the water.
With the level of verification, the flat itself for the measurement of the base surface, the placement should be stable, with the autocollimator test, the instrument and the plate is not the same rigid body. Instrument stent firmness is particularly important. Therefore, the verification procedures require that the test site should be stable, the test site should avoid vibration.
For the test personnel in the large plate on the test when the mobile, more consideration should be given to the stability of the test site, pay attention to the impact of gravity changes.