Elkron MEDEA, Руководство по установке

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40 MEDEA Installation Manual
2.3
RS485 BUS
2.3.1
BUS dimensions and topologies
The BUS connects the various devices and supplies power and data. The overall length of the BUS must
be as short as possible. In the case of a star connection, the sum of all BUS stretches should not exceed
500 metres. Longer lengths of up to 1000 metres can be achieved by cascading.
To achieve this result and facilitate the wiring work, any of the topologies shown below can be used freely
in the system installation.
BUS splitter 80IT7410111 can be used if required by the system layout.
Figure 19 - BUS topologies
IMPORTANT Do not create closed loops with the BUS to avoid malfunctions.
Figure 20 - BUS with loop
As the RS485 BUS is pre-polarised, no termination of lines using resistors is normally required. Only in
special cases is it advisable to
w s s , yp y b w Ω Ω,
prevent abnormal operation.
The BUS cable sizing is only calculated to determine the cross-section area of the "
+ " and " - " power cables.
9
9
9
9
9
9
B
V
9
B
V
9
B
V
9
B
V
9
B
V
9
B
V
9
B
V
9
B
V
9
B
V
9
Cascade
a
Star
Mixed