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GUIDELINES FOR RS-485 BUS CONNECTION
RS-485 standard
RS-485 standard is based on a balanced signals system. This means that two signals are ideally one opposed
to each other, respect to the ground.
It is strongly suggested that the transmission line will be formed by a “twisted pair” cable. This kind of cable
is particularly immune to electromagnetic noise.
Transmission cable
In order to prevent any interference risks, a properly shielded cable should always be used, especially if you
are close to power signals (e.g. electric engines, inverters, relais).
We recommend to use cat. 5E cable or equivalent.
Generally speaking, the RS-486 transmission cable should be shielded and compliant to the following
specifications:
•
Cable capacity <=300pF/m
•
Line impedance 100 Ω ±15 Ω
•
Line resistance 140 Ω/km or 225 Ω
•
Cable type: copper twisted pair
Network connection
•
As far as possible, limit the RS-485 network to a main single line (one segment)
•
Limit the total length of the main line to a maximum of 1000 m
•
Do not connect more than 31 devices on the same RS-485 segment
•
Disconnect the line termination resistors (if any) on all the slave devices connected
•
For short networks (up to 30 m) no line termination resistor is needed
•
For more extended networks, it could be necessary to terminate the RS-485 line in the
following way:
Summary of Contents for RILHEVA II
Page 1: ...1 RILHEVA II USERMANUAL V 1 5...
Page 6: ...6 SYSTEMARCHITECTURE...
Page 8: ...8 DEVICEINSTALLATION Some installation examples follow...
Page 9: ...9...
Page 18: ...18...
Page 33: ...33 ITEMSIZES...