Owner's Manual

GDX-350 Sensor Transmitter
24 P/N: 5600-9001 Rev 2
CAUTION: Alarm relays have dry contacts and power must be supplied from an external
source. Contacts are rated for RESISTIVE loads. Inductive loads, such as contactor coils or
motors, may cause contact arcing, which shortens life and emits RFI into the sensor signals.
Use appropriate arcing snubbers and MOVs across inductive loads and keep wiring away
from signal wires. External wiring to TB3 (Remote Alarm Reset) should be shielded and
protected from noise spikes to prevent false Alarm Reset.
Figure 2-9: Alarm Relays/Modbus Option (P/N 5600-0007)
STEP Alarms/RS-485 Modbus Option Installation
1.
Unscrew the cover on the GDX-350 explosion-proof enclosure.
2.
Loosen the two thumbscrews holding the display assembly in place and remove.
3.
A small ribbon cable is attached with sufficient length to access the back of the Display
assembly where the Alarms/RS-485 Modbus board option is located. It is possible to use only
relays, only RS-485, or both. Relay terminals are labeled NO (normally open), NC (normally
closed) and C (common, or the pole).
These designators correspond to the shelf, or de-energized, state of the relays. The FAULT
relay is always failsafe, meaning it is energized when there is not a fault condition and
therefore its action is reverse of the designators.
4.
RS-485 Modbus networks should be wired as shown in Figure 2-10. Each GDX-350
connected represents an RTU and must have a unique RTU address. RTU addresses are
assigned in the Modbus setup menu described in Section 5.14 on page 44.
5.
Cabling must be a “daisy chain” as opposed to a “star” pattern for reliable operation.
6.
The “end of line” unit should have J1 installed in the ‘A’ position for terminating resistor
installation. All others should have J1 in the ‘B’ position.
NOTE: Front panel Rx/Tx LEDs are helpful troubleshooting tools.