User Manual

9-2 ADS TRITON+ Manual
Establishing a Modbus Connection
The SCADA or process control system co nnects to the TRITON+
either through a serial connection using the ADS ExPAC (which
may be house d within the ADS XBUS
™
or a customer-supplied
enclosure) or through a cellular wireless modem in the monitor
using Modbus TCP.
Setting Up a Serial Connect ion
Two Modbus ports are available on the ExPAC thro ugh which to
communicate: RS-232 and RS-485.
Note: When both connections are available, ADS
rec ommends using the RS-485 connection. It has a greater
immunity to noise, supports longer cable runs without
signal degradatio n, and is easier to wir e .
The required port settings are 19200 baud rate, 8 data bits, no
parity, 1 stop bit, and no flow control.
Connecting through the RS-485 Port
When using an RS-485 connection for Modbus communications,
choose a cable that is no longer than 400 0 feet (1219 m) in length
with 24-gauge wiring. The cable must include at least one twisted
pair and one ground wire. If the cable extends beyond 1000 feet
(305 m), ADS recommends using 120 ohm termination resistors at
each end of the cab le.
Connect the cable to the ExPAC in the following wa y:
1. Disconnect (i.e., unplug) the green ter minal connector from the
RS-485 port on the top, left side of the ExPAC.