Emerson AMS Trex User Manual page 188

Troubleshooting
Symptom
Control system is
communicating HART, but the
Trex unit is not communicating
properly.
A HART device appears at the
multiple addresses.
When the Trex unit tries to
power a device, a message
stating voltage still detected at
HART terminals appears.
180
Possible cause
Device may be set to a HART
address other than zero
(multidrop mode).
An internal fuse may be blown.
HART communication is being
prevented by the control
system.
More than one Trex unit or
other secondary master may be
attached to the control loop.
The incorrect polling addresses
may be used.
HART Universal Revision 5 (or
earlier), 6, and 7 devices are on
the same loop.
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.
Solution
Change the polling mode to
Poll by Address.
Connect a meter capable of
measuring M ohms to the
HART or mA terminals. An
OPEN reading may indicate a
blown fuse.
Stop HART communications on
the control system and verify if
communication between the
devices and the Trex unit is
restored.
Ensure there is only one
primary master and one
secondary master on the
control loop.
Change the addresses being
polled.
Put HART Universal Revision 5
or earlier devices on a separate
loop from HART Universal
Revision 6 or 7 devices.
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.
User Guide