Emerson AMS Trex Device Communicator User Manual page 180

Troubleshooting
September 2021
A.1.1
180
1.800.561.8187
Symptom
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.
The Trex unit needs to supply
more current than the typical 4
mA to power a positioner. This
can occur when the positioner
needs more current to power
the CPU at faster speed for
diagnostics.
HART loops
Verify the HART loop current and voltage on the device. Almost all devices need at least 4
mA and 12V DC to operate properly. If there are multiple devices on a multidrop loop, set
www.
Possible cause
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.
Use the device connection
wizard in the Field
Communicator application to
increase mA.
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User Guide
Solution
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.
1. In the Field Communicator
application, connect to
the positioner.
2. Change its polling address
to a non-zero value.
3. Disconnect the positioner,
and restart the Field
Communicator
application.
4. Tap HART.
5. Tap Yes when prompted if
you want to provide
power from the Trex unit.
6. Tap Positioner.
7. Tap Yes when prompted
to increase current.
8. Select the current value.
User Guide