Carel GDWB, User Manual

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11
ENG
+0300046IE - rel. 1.2 - 14.01.2021
RS485 Modbus
RS485 Modbus remote serial line
A
cc
ess P
oin
t
Rout
er Br
idge
other
third-
party
devices
RS485 Modbus
4-20 mA 4-20 mA
0-10 V 0-10 V
Fig. 2.a Fig. 2.b
Fig. 2.c Fig. 2.d
2.4.4 RS485 Modbus RTU interface
For the RS485 Modbus network, use a 3-wire shielded cable; for more
information see chapter “5 - Technical specifications”.
Recommended: Belden 3106A (or equivalent).
The parameters for Modbus communication can only be set using the
Rileva app. Therefore no hardware settings are required on the device.
Make sure that the network communication parameters are configured
in the same way, including on the supervisor.
To ensure optimal operation of the serial network, observe the following
guidelines:
•
make sure that the devices are configured with a single bus layout;
connecting several buses in parallel, or branching several devices
from the main bus may introduce incorrect combinations of signal
impedance, reflections and/or distortions.
•
Avoid using excessively long connections when connecting devices
to the serial bus. The device - bus connection must not exceed a
maximum length of 1 metre.
•
Make sure that the devices at the end of the bus have the 120 Ω
termination enabled. The termination resistance can be enabled using
the Rileva app.
•
Make sure that the polarity of the A (+, Tx) / B (-, Rx) signal is maintained
across the serial network.
•
Earth the cable shield only on the main unit side.
•
Connect the cable shield to terminal SH on the gas detector.
•
Make sure that the shield is intact across the serial network.
•
Do not use the shield connection as a signal reference. Use a cable that
provides a dedicated wire for the signal reference. Connect the signal
reference to terminal GND on the gas detector.
2.4.5 Completing installation
Once all of the wiring is complete, refit the gas detector cover and power
on.
Check correct operation of the device, the start-up warm-up phase and
communication with the devices connected to the gas detector.
Finally, carry out a bump test or calibration, if necessary.