Wednesday, March 11, 2020

FUNDAMENTALS OF SURVEYING : Functions of clamp and tangent screws.


  Functions of clamp and tangent screws.
1)             Clamp screws:
 When the upper clamp screw is tightened and lower clamp screw is loose, the instrument rotates about outer axis, without any relative motion between plates. The vernier reading do not change.
 When lower clamp screw is tightened, but the upper clamp screw is loose, the instrument rotates about the inner axis with a relative motion between the tow plates. The vernier reading changes.
 If both the clamp screw are tightened instrument cannot rotate at all.
2)             Tangent screws for small movement ofplates or for accurate fixing ofplates corresponding tangent screw (corresponding to plates) are used. Permanent adjustment of theodolite:

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