Rs-485 Wiring - Emerson Rosemount 370XA System Reference Manual

System Reference Manual
7P00370-H01
3.10.2

RS-485 wiring

NOTICE
The terminating resistors shown in the graphic above are not required for most
installations but may help in reducing communication errors for long distance or
multi-dropped applications.
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The RS-485 protocol is suitable for longer distance
communications and also allows multi-dropped communication
to multiple devices.
For long distance RS-485 communications, wire 100 ohm to
120 ohm terminating resistors in parallel to the two endpoint
terminals.
If the GC is connected with multiple devices on an RS-485 link,
terminating resistors should only be installed at the two end
points.
370XA Gas Chromatograph
APRIL 2014