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4.14
Installation locations
Siemens Building T
echnologies
Cerberus Division
When installation locations are rigid and vibration-free even a large temperature fluctua-
tion (e.g. between day and night) has only slight influence on steel girders and therefore
does not greatly alter the structure of a building. However, if the installation location is not
rigid, the closely bundled infrared beam can quickly wander from the receiver and so
cause an alarm or trouble signal. Unstable installation locations include:
the walls of rooms constructed of steel which expand and contract due to the tempera-
ture coefficient of steel
masonry walls on which a steel roof has been constructed
In such cases the DLO1191 must be mounted on the rigid structural element, meanwhile
the reflector can be mounted on the instable wall.
Roof length = 80m
Reflector
Fig. 23 Deflection of the IR beam caused by heat on the steel roof
The linear expansion of steel:
l (mm) x ∆T (°C) x linear coefficient of expansion (0.000012) = mm
Example:
80,000 x 30 x 0.000012 = 28.8mm
DLO11..
Fig. 24 Possible solution by mounting of the DLO1191 on the stable surface and mount-
ing of the reflector on the instable wall
DLO11..
incorrect
Reflector
correct
28.8mm
0,43°
3.83m
e1276e
09.2000
27
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