Automatic Levelling; Accuracy Check Of The Measuring Tool - Bosch GCL 25 Professional Manual Original

14 | English
All point beams run at a 90° angle to each other and the laser
lines intersect at a 90° angle.
Once switched on, the measuring tool is in the cross-line and
point mode. To change the operating mode, press the laser
mode button (2).
All operating modes can be selected with or without auto-
matic levelling.

Automatic Levelling

Working with automatic levelling (see figures C–E)
Position the measuring tool on a level, firm surface or attach
it to the holder (15) or the tripod (16).
For work with automatic levelling, slide the on/off switch (4)
to the " On" position.
The automatic levelling function automatically levels irregu-
larities within the self-levelling range of ±4°. The levelling is
finished as soon as the laser points and/or laser lines do not
move any more.
If automatic levelling is not possible, e.g. because the sur-
face on which the measuring tool stands deviates by more
than 4° from the horizontal plane, the laser beams begin to
flash. This alarm is deactivated within 10 s after switching
on, in order to allow the measuring tool to be adjusted.
Place the measuring tool in a horizontal position and wait for
self-levelling to take place. As soon as the measuring tool is
within the self-levelling range of ±4°, the laser beams will
light up continuously.
In case of ground vibrations or position changes during oper-
ation, the measuring tool is automatically levelled again.
After each levelling process, check the position of the hori-
zontal and/or vertical laser beams in relation to the refer-
ence points to avoid errors arising from a change in the
measuring tool's position.
Working without automatic levelling (see figure F)
For work without automatic levelling, slide the on/off
switch (4) to the " On" position. When automatic levelling
is switched off, the laser beams flash continuously.
Switching off the automatic levelling function allows you to
hold the measuring tool freely in your hand or place it on a
sloping surface. This means that the laser beams no longer
necessarily run perpendicular to one another.

Accuracy Check of the Measuring Tool

Influences on Accuracy
The largest influence is exerted by the ambient temperature.
In particular, temperature differences that occur from the
ground upwards can refract the laser beam.
Since the temperature stratification is greatest at ground
level, you should mount the measuring tool on a tripod and
position it in the centre of the work surface, wherever this is
possible.
In addition to external influences, device-specific influences
(e.g. falls or heavy impacts) can also lead to deviations. For
this reason, check the levelling accuracy each time before
beginning work.
1 609 92A 4HF | (20.08.2018)
If the accuracy of the horizontal point beams is within the
maximum permitted deviation, this means the accuracy of
the vertical point beams and the laser lines has also been
verified.
If the measuring tool exceeds the maximum deviation in one
of the checks, it should be sent to the Bosch after-sales ser-
vice for repair.
Checking the horizontal levelling accuracy of the
longitudinal axis
For this check, you will need a free measuring distance of
20 m on firm ground between two walls (designated A
and B).
– Mount the measuring tool close to wall A on the holder
(15) or a tripod, or place it on a firm, level surface.
Switch on the measuring tool and select five-point mode
with automatic levelling.
A
20 m
– Aim the horizontal laser beam that runs parallel to the lon-
gitudinal axis of the measuring tool at the closer wall A
and allow the measuring tool to level in. Mark the centre
of the laser point on the wall (point Ⅰ).
A
180°
– Turn the measuring tool 180°, allow it to level in and mark
the centre point of the laser beam on the opposite wall B
(point Ⅱ).
– Position the measuring tool – without rotating it – close to
wall B, switch it on and allow it to level in.
B
B
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