6. Measure the vertical distances between marks d1=a1-a2, d2=a1-a3 that indicate
the actual deviation of the instrument.
If any of the actual deviations is greater than the Allowable Deviation for the corresponding
Distance to Wall in the following table, the instrument must be serviced.
Distance to Wall
16' (5m)
30' (9m)
Allowable Deviation
5/32" (4mm)
5/16" (8mm)
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Step 3: Checking the Leveling Accuracy of the Vertical Line
For this check, the most practical recommendation is to consider a door opening with
at least 7' (2m) of height clearance and 8' (2,5m) of space to each side of the opening.
1. Position the instrument directly on a firm, level floor surface 8' (2,5m) away from
the door opening.
2. Turn on the instrument in the self-leveling mode by sliding the Pendulum Switch
to the UNLOCK position.
3. Direct the vertical laser beam to the center of the opening and allow a few seconds
for the visible laser line to stabilise.
4. Mark the center of the vertical laser line projected by the instrument in three locations:
on the floor at the center of the door opening (point a), at an 8' (2,5m) distance beyond
the other side of the door opening (point b), and at the upper edge of the door opening
(point c1).
c1
b
a
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2