Installation
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0
1
8
-1
2
55
In accordance with DIN EN 61158 and DIN EN 61784, the following principles apply:
n
Linear bus structure without branches, consisting of a cable with terminators
n
Length of the spur to the node < 0.3 m
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Total length of all spurs < 6 m
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Data transfer via shielded twisted pair cable
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Terminator 100 ... 130
Ω
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Core cross section > 0.22 mm
²
, approx. 60 pF/m
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Max. 32 active or passive nodes including repeaters
n
Max. 3 repeaters between 2 nodes
n
Max. cable length 1200 m, depending on the transfer rate
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The FOL7250* PROFIBUS fiber optic coupler and repeater enables the transfer of data at
high speeds over long distances (1000 m at 1.5 Mbit/s).
Terminators
The RS-485 fieldbus must have exactly two terminators per segment, one at the start and one
at the end. A segment usually starts at the master, while the last remote I/O unit is taken to be
the end of the segment. A segment also ends or begins at a repeater or a fiber optic cable.
To install a terminator, use the following bus termination modules.
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Terminator for a service bus: FB9293*
n
Terminator for a fieldbus: FB9294*
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Terminator for a service bus and a fieldbus: FB9295*
Figure 3.25
Block diagram for FB9293*, FB9294*, FB9295*
Zone 1
FB9293
FB9294
FB9295
Example!
A bus with 3 segments, 1 master, a fiber optic cable transfer path, 4 nodes, and 1 repeater has
6 terminators (T).
Master(
T
)
—
Node
—
(
T
)Fiber optic cable(
T
)
—
Node
—
(
T
)Repeater(
T
)
—
Node
—
(
T
)Node