Manual

140
DXi User Manual
Appendix E: Hardwired Communication Troubleshooting
Inspecting Field Wiring:
Field wiring problem causes vary, but all typically result in a few types of failures, such
as additional resistance, open circuit, short circuit and/or ground leakage.
Typical causes for these failures are a severed wire, poor/defective wire splice,
defective wire insulator, water ingress or installation of the incorrect/poor quality
underground communication cable. To test for these faults, try the following:
Test 1
Run a new communication cable above ground to the suspect controller. Exercise
large communication to the controller from Laguna and monitor the controller
communication diagnostic screen, communication board indication LEDs and
generation of communication alerts.
Failure to observe normal operating behavior is indicative of a bad hardware module
or inter hardware ribbon connectors (not a field wiring issue).
Test 2
Power down the suspect controller, upstream controller and downstream controller.
Disconnect the communication cable from the suspect control. Connect the "IN"
positive and negative wires together. Connect the "OUT" positive and negative wires
together.
Disconnect the "OUT" communication cables from the upstream controller and
probe resistance with multi-meter. Disconnect the "IN" communication cables from
the downstream controller and probe resistance with multi-meter.
The resistance value probed for the "IN" and "OUT" lines should be proportional to
the total field wire length run. EV-CAB-COMM has a resistance of 0.0333 Ohms/
Meter. If the total wire length (up and back), is 250 meters, this should yield a
resistance value of approx. 8 ohms (0.0333 ohm/meter * 250 meters = 8 ohms).
A higher than expected resistance value is indicative of poor splices or incorrect/poor
quality cable.
An extremely high or open circuit value is indicative of a severed wire.
A lower than expected resistance value is indicative of a shorted wire.
Test 3
Power down the suspect controller, upstream controller and downstream controller.
Disconnect the communication cable from the suspect controller, for both the "IN"
and "OUT" connections.
Using a multi meter, make a resistance measurement between the disconnected "IN
+" field wire and the enclosure chassis. Repeat the resistance measurement for the
"IN -", "OUT +, and "OUT -" with respect to the chassis.
The resistance values measured can range depending on the communication
type, enclosure type and EV-CAB-COMM wire shield grounding. Valid Approx.
measurement values for this test are:
OUT- ≈ 3.1K ohm, Mega ohms or Open Circuit