Publicité
used as a signal common or ground. The table below lists typical cable
recommendations.
RS-232
Up to 15m (50ft) virtually any standard shielded twisted pair with drain (Belden 9502 or
equivalent).
RS-422 and RS-485
Up to 1200m (4000ft) 24 AWG twisted pair with foil shield and drain wire on each pair
(Belden 9841 for 2-wire and 9729 for 4-wire or equiv.).
3.10 Network topology
Various kinds of network topologies may be done on the basis of an RS485 Modbus
network.
The Modbus network may be managed by a computer collecting data. Typically this
computer runs an OPC server connected to a plant intranet. OPC client applications may
present this information to any supervision program that will perform the Human
machine interface, data logging, and data setting ...
It is also possible to manage the RS485 Modbus network through a PLC.
Various kind of RS485 to RS232 converters exists.
To bridge the Modbus network to another kind of software protocol, various kinds of
protocol converters may be used. They are often called 'protocol gateway: Modbus to
Profibus, Ethernet, CAN ...
8 Serial interface considerations ç RS485
Publicité
