Bosch GRL Professional Series Original Instructions Manual page 26

OBJ_BUCH-757-007.book Page 25 Tuesday, June 21, 2011 10:16 AM
Levelling Accuracy of the Rotational Laser Level
Influences on Accuracy
The ambient temperature has the greatest influence. Espe-
cially temperature differences occurring from the ground up-
ward can divert the laser beam.
The deviations play a role in excess of approx. 20 m measur-
ing distance and can easily reach two to four times the devia-
tion at 100 m.
Because the largest difference in temperature layers is close
to the ground, the measuring tool should always be mounted
on a tripod when measuring distances exceeding 20 m. If pos-
sible, also set up the measuring tool in the centre of the work
area.
Accuracy Check of the Measuring Tool
Apart from exterior influences, device-specific influences
(such as heavy impact or falling down) can lead to deviations.
Therefore, check the accuracy of the measuring tool each
time before starting your work.
For the accuracy check, an unobstructed measuring distance
of 20 m on firm ground between two walls A and B is required.
With the measuring tool in the horizontal position, a transit
measurement is to be carried out across both axes X and Y
(both positive and negative) (altogether 4 complete measure-
ments).
– Mount the measuring tool in the horizontal position onto a
tripod 37 (accessory) or place it on a firm and level surface
near wall A. Switch the measuring tool on.
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– After levelling, direct the laser beam in point operation on-
to the close wall A. Mark the centre point of the laser beam
on the wall (point I).
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– Turn the measuring tool around by 180°, allow it to level in
and mark the centre point of the laser beam on the oppo-
site wall B (point II).
Bosch Power Tools
– Without turning the measuring tool, position it close to wall
B. Switch the measuring tool on and allow it to level in.
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– Align the height of the measuring tool (using the tripod or
by underlaying, if required) in such a manner that the cen-
tre point of the laser beam is projected exactly against the
previously marked point II on wall B.
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– Rotate the measuring tool by 180° without changing the
height. Allow it to level in and mark the centre point of the
laser beam on wall A (point III). Take care that point III is
as vertical as possible above or below point I.
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– The difference d of both marked points I and III on wall A
amounts to the actual deviation of the measuring tool for
the measured axis.
Repeat the measuring procedure for the other three axes. For
this, turn the measuring tool prior to each measuring proce-
dure by 90°.
On the measuring section of 2 x 20 m = 40 m, the maximum
allowable deviation is:
40 m x 0.1 mm/m = 4 mm.
Consequently, the difference d between points I and III for
each of the four individual measurements may not exceed
4 mm max.
If the measuring tool should exceed the maximum deviation in
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anyone of the four measuring procedures, have it checked at
a Bosch after-sales service agent.
Working Advice
Always use the centre of the laser point for marking.
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The size of the laser point changes with the distance.
Laser Viewing Glasses (Accessory)
The laser viewing glasses filter out ambient light. This en-
hances the laser visibility for the eye.
Do not use the laser viewing glasses as safety goggles.
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The laser viewing glasses are used for improved visualisa-
tion of the laser beam, but they do not protect against laser
radiation.
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