Emerson Rosemount 644 with HART Protocol, Reference Manual

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76
Reference Manual
00809-0200-4728, Rev SA
Troubleshooting
July 2018
Troubleshooting
6.3 4–20 mA/HART output
Table 6-1. Troubleshooting 4–20 mA Output
Symptom or
issue Potential
source
Corrective action
Transmitter does
not communicate
with Field
Communicator
Loop wiring

Check the revision level of the transmitter device descriptors (DDs) stored in
your communicator. The communicator should report Dev v4, DD v1
(improved), or reference
“Field Communicator” on page 6 for previous
versions. Contact Emerson
™
Customer Central for assistance.

Check for a minimum of 250 ohms resistance between the power supply and
Field Communicator connection.

Check for adequate voltage to the transmitter. If a Field Communicator is
connected and 250 ohms resistance is properly in the loop, then the
transmitter requires a minimum of 12.0 V at the terminals to operate (over
entire 3.5–23.0 mA operating range), and 12.5 V minimum to communicate
digitally.

Check for intermittent shorts, open circuits, and multiple grounds.
High output
Sensor input
failure or
connection

Connect a Field Communicator and enter the transmitter test mode to check
for a sensor failure.

Check for a sensor open or short circuit.

Check the process variable to see if it is out of range.
Loop wiring

Check for dirty or defective terminals, interconnecting pins, or receptacles.
Power supply

Check the output voltage of the power supply at the transmitter terminals. It
should be 12.0–42.4 Vdc (over entire 3.75–23 mA operating range).
Electronics

Connect a Field Communicator and enter the transmitter status mode to
isolate module failure.

Connect a Field Communicator and check the sensor limits to ensure
calibration adjustments are within the sensor range.
Erratic output
Loop wiring

Check for adequate voltage to the transmitter. It should be 12.0–42.4 Vdc at
the transmitter terminals (over entire 3.75–23 mA operating range).

Check for intermittent shorts, open circuits, and multiple grounds.

Connect a Field Communicator and enter the Loop test mode to generate
signals of 4 mA, 20 mA, and user-selected values.
Electronics

Connect a Field Communicator and enter the transmitter test mode to isolate
module failure.