Pepperl+Fuchs FieldConnex HD2-DM-A Manual page 98

Use Cases and Troubleshooting
Fault Type
Segment DC unbal-
ance alarms
Segment/field de-
vice level high
alarm
Subject to reasonable modifications due to technical advances.
98
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Fault Clearance
• Check that the bus segment wiring is correct
and that there is no pole-to-shield fault
• Check that there is no ingress of dirt or water
causing a resistive connection between a pole
of the bus cable and the cable shield (e. g. in a
slave housing, junction box etc.)
• If an isolated system is used, it is possible to de-
termine the defective segment directly
• If a non-isolated system is used, all galvanically
connected segments transmit an unbalance er-
ror; disconnect single segments to find out,
which segment has caused the error (using a re-
dundant system, it is possible, to exchange pow-
er conditioner modules segment by segment
isolated power supply modules running, without
shutting down the bus to find out, which bus seg-
ment is affected)
• Check if the bus segment is terminated correctly
(one terminator at each end of the bus segment
cable)
• Check that the bus cable is healthy and that
there is no disruption of the wiring
• Check if the positions of the field devices have
been changed (signal level is dependent on the
field device position, due to bus cable resis-
tance)
• Check which field device address is causing the
level alarm and if necessary replace the device
• If you are using the DM-A connected to a spur
line, repeat the measurement on the trunk. (In
seldom cases doubled signal level occurs by
measuring on a spur line)
• Use the integrated scope function for further ex-
amination
H D 2 - D M - A / D M - A M
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