Siemens SIMATIC NET PROFIBUS Instrukcje Operacyjne Pobierz pdf (Strona 43)

Installation and Maintenance

5.3 Connection of the Electrical RS-485 Bus Cables

SIMATIC NET PROFIBUS Optical Link Module OLM V4.0

Operating Instructions, 01/2013, C79000-G8976-C270-03

 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 via 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.

 All PROFIBUS bus connectors of the network must be screwed securely to the RS-485

ports.

 Connecting or removing the bus connector or loosely connected bus connectors or bus wires

not secure inside the connectors can lead to disruptions in the optical and electrical network.

 Connect or remove the RS-485 bus connector sharply and without tilting or levering 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 line acts like an antenna and is

susceptible to noise.

 In order to minimize disturbances, keep to the following order when connecting an RS-485

bus cable to a PROFIBUS OLM when the network is active:

1. Plug the RS-485 bus connector onto the relevant device (e.g. the programming device)

and secure it with the screws.

2. Insert the RS-485 bus connector in the PROFIBUS OLM with a sharp movement and

without tilting the connector.

Carry out the 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 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.

Compatibility notice:

In the OLM V3, pin 2 was additionally connected with ground and pin 1 with the shield. This

does

not conform with the relevant standard EN 50170 /2/. This presents no problem, when

cables complying with the PROFIBUS standard are used. When installing in an existing cabling

system, check the pin assignment and modify it if necessary.

Please note the following safety information:

Do not connect RS-485 bus cables to the OLM that are laid completely or partly outside

buildings. Lightning strikes in the vicinity could otherwise destroy the modules. If the bus exits

the building, use fiber-optic cables!

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Siemens SIMATIC NET PROFIBUS Instrukcje Operacyjne Strona 43