Working Without Automatic Levelling - Bosch Professional GLL 3-50 Manual Original

OBJ_BUCH-1973-002.book Page 15 Thursday, October 10, 2013 4:45 PM
beams flash. In this case, bring the measuring tool to the level
position and wait for the self-levelling to take place.
In case of ground vibrations or position changes during opera-
tion, the measuring tool is automatically levelled in again. To
avoid errors, check the position of the horizontal and vertical la-
ser line with regard to the reference points upon re-levelling.

Working without Automatic Levelling

For work without automatic levelling, push the On/Off switch
14 to the " on" position. When the automatic levelling is
switched off, the laser lines flash continuously.
When the automatic levelling is switched off, the measuring
tool can be held by hand or placed on an inclined surface. In
cross-line operation, the two laser lines do not necessarily run
at a right angle to each other.
Levelling Accuracy
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.
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.
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.
First, check both the height as well as the levelling accuracy of
the horizontal laser line, then the levelling accuracy of the ver-
tical laser line.
Should the measuring tool exceed the maximum deviation
during one of the tests, please have it repaired by a Bosch af-
ter-sales service.
Checking the Height Accuracy of the Horizontal Line
For this check, a free measuring distance of 5 m on a firm sur-
face between two walls A and B is required.
– Mount the measuring tool onto a tripod or place it on a firm
and level surface close to wall A. Switch on the measuring
tool. Select cross-line operation with automatic levelling.
A
5 m
– Direct the laser against the close wall A and allow the meas-
uring tool to level in. Mark the centre of the point where the
laser lines cross each other on the wall (point I).
Bosch Power Tools
A
180˚
– Turn the measuring tool by 180°, allow it to level in and
mark the cross point of the laser lines on the opposite wall
B (point II).
– Without turning the measuring tool, position it close to wall
B. Switch the measuring tool on and allow it to level in.
A
– Align the height of the measuring tool (using a tripod or by
underlaying, if required) in such a manner that the cross
point of the laser lines is projected against the previously
marked point II on the wall B.
A
d
– Without changing the height, turn around the measuring
tool by 180°. Direct it against the wall A in such a manner
that the vertical laser line runs through the already marked
B
point I. Allow the measuring tool to level in and mark the
cross point of the laser lines on the wall A (point III).
– The difference d of both marked points I and III on wall A
indicates the actual height deviation of the measuring tool.
The maximum permitted deviation d
d = double distance of the walls x 0.3 mm/m
max
Example: With a 5 metre distance between the walls, the max-
imum deviation must not exceed
d = 2 x 5 m x 0.3 mm/m = 3 mm. Thus, the marks must not
max
be more than 3 mm apart.
English | 15
B
B
B
180˚
is calculated as follows:
max
1 618 C00 99J | (10.10.13)