Symptom Possible cause Solution
Device may be set to a HART
address other than zero
(multidrop mode).
Change the polling mode to
Poll by Address.
Control system is
communicating HART, but the
Trex unit is not communicating
properly.
An internal fuse may be blown. Connect a meter capable of
measuring M ohms to the
HART or mA terminals. An
OPEN reading may indicate a
blown fuse.
HART communication is being
prevented by the control
system.
Stop HART communications on
the control system and verify if
communication between the
devices and the Trex unit is
restored.
More than one Trex unit or
other secondary master may be
attached to the control loop.
Ensure there is only one
primary master and one
secondary master on the
control loop.
A HART device appears at the
multiple addresses.
The incorrect polling addresses
may be used.
Change the addresses being
polled.
HART Universal Revision 5 (or
earlier), 6, and 7 devices are on
the same loop.
Put HART Universal Revision 5
or earlier devices on a separate
loop from HART Universal
Revision 6 or 7 devices.
When the Trex unit tries to
power a device, a message
stating voltage still detected at
HART terminals appears.
This message can appear if the
Trex unit connects to a device
that was recently powered.
Some devices may hold voltage
for several minutes after the
power is removed.
The Trex unit asks if you want
to ignore the voltage warning
and proceed with sourcing
power. If you select Yes, Trex
powers the device. You can
also wait a few minutes before
connecting to and powering
the device.
Troubleshooting
180 User Guide
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