e1276e
27
Siemens Building T
echnologies
Cerberus Division
09.2000
4.14
Installation locations
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.
Reflector
incorrect
DLO11..
0,43
°
28.8mm
3.83m
Roof length = 80m
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
Reflector
DLO11..
correct
Fig. 24 Possible solution by mounting of the DLO1191 on the stable surface and mount-
ing of the reflector on the instable wall
