SI-Ethernet User Guide 13
Issue: 1
Safety
information
Introduction
Mechanical
installation
Electrical
installation
Getting started Parameters
Key features
and Protocols
PC Applications Security Diagnostics
Glossary of
terms
Index
4.4 Cable shield connections
Standard Ethernet UTP or STP cables do not require supplementary grounding.
4.5 Cable
It is recommended that a minimum specification of CAT5e is installed on new
installations, as this gives a good cost/performance ratio. If you are using existing
cabling, this may limit the maximum data rate depending on the cable ratings. In noisy
environments, the use of STP or fiber optic cable will offer additional noise immunity.
4.6 Maximum network length
The main restriction imposed on Ethernet cabling is the length of a single segment of
cable as detailed in Table 4.1. If distances greater than this are required it may be
possible to extend the network with additional switches or by using a fiber optic
converter.
4.7 Network topology
The SI-Ethernet option module and onboard Ethernet interface support multiple network
topologies this allows the user to design a robust network using the topology that works
best for the chosen design.
Star topology:
• Enables individual devices to be swapped out
• Minimise message transmission delays
Line topology (daisy chain):
• Simple wiring
• Lowest cost
Tree topology:
• Maximises bandwidth - contains messages within appropriate segments
• Products can be connected in functional groups, e.g. to enable one section of a
machine to be turned off
Cabling issues are the single biggest cause of network down-time. Ensure cabling is
correctly routed, wiring is correct, connectors are correctly installed and any switches or
routers used are rated for industrial use. Office grade Ethernet equipment does not
generally offer the same degree of noise immunity as equipment intended for industrial
use.
Table 4.1 Ethernet maximum network lengths
Type Of Cable Data rate (bit/s) Maximum trunk length (m)
Copper - UTP/STP CAT 5
100 M
100
Fiber Optic - Multi-mode 3000
Fiber Optic - Single-mode up to 100000
The distances specified are absolute recommended maximums for reliable transmission
of data. The distances for the fiber optic sections will be dependent on the equipment
used on the network. The use of wireless networking products is not recommended for
control systems, as performance may be affected by many external influences.
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