6.7 Optical plummet
Inspection
1Place a piece of white paper, with a cross drawn on it, directly under the instrument.
2Look through the optical plummet, and move the paper so that the intersecting point of the cross comes to the center of the field of view.
3Adjust the leveling screws so that the center mark of the optical plummet coincides with the intersection point of the cross.
4Rotate the instrument around the vertical axis. Look through the optical plummet each step of 90° rotation, and observe the center mark position against the intersection point of the cross.
5If the center mark always coincides with the intersection point, no adjustment is necessary. When it does not coincide, the following
adjustments are required.
Point
Center mark
Adjustment
1Remove the cover of the optical plummet.
2Mark the point set on the line of sight at each step of 90° on the white paper and call them A,B, C and D.
3Join the opposed points (A, C and B, D) with a straight line, and set intersecting point 0.
4Turn four optical plummet adjusting screws with the adjusting pin so that the center mark coincides with the intersection point 0.
5Repeat procedure again to confirm.
Optical plummet adjusting screw
Adjusting pin for the center mark
Cap of optical plummet
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