CMVETH01B
8
Installation
3.2.3 Cabling
To ensure long-term reliability it is recommended that any cables used to connect a system together are
tested using a suitable Ethernet cable tester, this is of particular importance when cables are made up on
site. 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.
3.2.4 Maximum Network Length
The main restriction imposed on Ethernet cabling is the length of a single section of cable as detailed
in Table 3. 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. Cabling issues are the single biggest cause of
network downtime. Ensure cabling is correctly routed, wiring is correct, connectors are properly fitted and
any switches or routers used are rated for industrial use. Office grade Ethernet equipment does not offer
the same degree of noise immunity as equipment intended for industrial use.
Table 3: Maximum Network Length
Type of Cable
Data Rate (bits/sec)
Maximum Trunk Length (m)
Copper - UTP/STP CAT 5
10M
100
Copper - UTP/STP CAT 5
100M
100
Fiber Optic - Multi-mode
10M
2000
Fiber Optic - Multi-mode
100M
3000
Fiber Optic - Single-mode
10M
no standard
Fiber Optic - Single-mode
100M
up to 100000
NOTE
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.
3.2.5 Minimum Node to Node Cable Length
There is no minimum length of cable recommended in the Ethernet standards for UTP or STP. For
consistency across fieldbus modules, a minimum network device-to-device distance equal to 1 meter of
cable is recommended. This minimum length helps to ensure a good bend radius on cables and avoids
unnecessary strain on connectors.
