Owner's Manual

GDX-350 Sensor Transmitter
P/N: 5600-9001 Rev 2 23
STEP 3-WIRE 4-20 mA MODE INSTALLATION
1.
Unscrew the cover on the GDX-350 explosion-proof enclosure.
2.
Loosen the 2 thumbscrews holding the display assembly in place and remove it
(refer to
Figure 2-8). A small ribbon cable is attached with sufficient length to allow access to the I/O
PCB mounted in the bottom of the enclosure.
3.
Power and signal connections are to TB2 where 24 VDC, Signal and Common wires must be
connected. A blocking diode protects the GDX-350 if polarity of the power supply is reversed,
but it will not operate.
4.
Reassemble the GDX-350. Follow the procedures and recommendations in the receiver and
power supply manuals to complete the installation.
5.
Be sure the GDX-350 enclosure and conduit are properly grounded. Apply power and observe
that the GDX-350 functions.
Figure 2-8: 5600-0006 I/O Power Supply/3-Wire 4-20 mA Assembly
2.9. Alarms/RS-485 Modbus Option Installation
The optional Alarms/RS-485 Modbus board (P/N 5600-0007) supplies two level alarm relays: a FAULT
relay and an RS-485 Modbus RTU slave port (Figure 2-9). This board is “piggybacked” behind the
Display Assembly (P/N 5600-0005) as shown in Figure 2-8. Addition of this option requires 3-wire mode,
4-20 mA operation and thereby requires the I/O Power Supply board (P/N 5600-0006) (Figure 2-8). This
is because relays and RS-485 circuits require much more power than 2-wire 4-20 mA loops can deliver.