Emerson Rosemount 644 HART, Reference Manual

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72
Reference Manual
00809-0100-4728, Rev MB
Troubleshooting
July 2016
Troubleshooting
6.3 Troubleshooting the 4-20 mA/HART 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 3-2 for previous versions. Contact
Emerson
™
Process Management 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 to 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 to 42.4 Vdc (over entire 3.75 to 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 to 42.4 Vdc at the
transmitter terminals (over entire 3.75 to 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.
Low or No
Output
Sensor
Element
•
Connect a Field Communicator and enter the Transmitter test mode to isolate a
sensor failure.
•
Check the process variable to see if it is out of range.
Loop Wiring
•
Check for adequate voltage to the transmitter. It should be 12.0 to 42.4 Vdc (over
entire 3.75 to 23 mA operating range).
•
Check for shorts and multiple grounds.
•
Check for proper polarity at the signal terminal.
•
Check the loop impedance.
•
Connect a Field Communicator and enter the Loop test mode.
•
Check wire insulation to detect possible shorts to ground.
Electronics
•
Connect a Field Communicator and check the sensor limits to ensure calibration
adjustments are within the sensor range.