Electrical Rs-485 Bus Cables - Siemens SIMATIC NET Operating Instructions Manual

Connection

6.1 Electrical RS-485 bus cables

6.1 Electrical RS-485 bus cables
Note
NOTICE
Damage
Do not connect any RS-485 bus cables that are laid entirely or partly outdoors. Otherwise,
lightning strikes in the vicinity can destroy the modules.
If you have bus connections that leave the building, use FO cables.
● Only use shielded twisted pair for the RS-485 bus cables as described in the manual
"SIMATIC NET PROFIBUS Networks". Do not exceed the segment lengths specified
there.
● Connect the RS-485 bus segment using a PROFIBUS connector. If the module is at the
beginning or at the end of a bus segment, this connector must have an active bus
terminator.
● Screw all PROFIBUS bus connectors of the network securely to the RS-485 interfaces.
● Disruptions can occur in the optical and electrical network as a result of
– Plugging or pulling the bus connector
– Loosely connected bus connectors
– Bus wires not being securely crewed inside the connectors
● Connect or remove the RS-485 bus connector quickly and without tilting or twisting the
connector.
● Disconnect the RS-485 bus cable from the OLM when there is no device at the other end
or when there is no power supplied to it. Otherwise the open cable acts like an antenna
and is susceptible to interference.
● To minimize disturbances, keep to the following order when connecting an RS-485 bus
cable to a PROFIBUS OLM when the network is active:
– Plug the RS-485 bus connector into the relevant device (e.g. the programming device)
– Plug the RS-485 bus connector into the PROFIBUS OLM quickly and without tilting or
– Carry out these steps in the reverse order to disconnect a device from the network.
● Make sure that the bus segment connected to the RS-485 port is terminated at both ends.
Only use a connecting cable that is terminated at both ends to connect a single device.
● If temperatures in excess of 70 °C can occur on the cables or at their insertion points or
the temperature at cable branching points can exceed 80 °C, special measures must be
taken.
● For ambient temperatures of 50 °C to 60 °C, cables with a temperature rating for at least
80 °C should be used.
44
and secure it with the screws.
twisting the connector and screw it tight.
Operating Instructions, 01/2020, C79000-G8976-C270-06
Optical link module