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Important
The HART signal over the primary mA output affects the mA reading. Disconnect the wiring
between the Field Communicator and the transmitter terminals when reading the primary
mA output at the receiving device. Reconnect to continue the trim.
3. Choose Service Tools > Maintenance > Routine Maintenance > Trim mA output 2.
4. Follow the instructions in the guided method.
5. Check the trim values, and contact Micro Motion customer service if any value is less
than −200 microamps or greater than +200 microamps.
10.14 Check the HART communication loop
If you cannot establish or maintain HART communications, the HART loop may be wired
incorrectly.
Prerequisites
You will need:
• A copy of your transmitter installation manual
• A Field Communicator
• Optional: the HART Application Guide, available at www.hartcomm.org
Procedure
1. Verify that the loop wires are connected as shown in the wiring diagrams in the
transmitter installation manual.
If your HART network is more complex than the wiring diagrams in the transmitter
installation manual, contact either Micro Motion or the HART Communication
Foundation.
2. Disconnect the primary mA output wiring from the transmitter.
3. Install a 250–1000 Ω resistor across the transmitter’s primary mA output terminals.
4. Check the voltage drop across the resistor (4–20 mA = 1–5 VDC).
If voltage drop is less than 1 VDC, add resistance to achieve a voltage drop of greater
than 1 VDC.
5. Connect a Field Communicator directly across the resistor and attempt to
communicate (poll).
If communication with the transmitter cannot be established, the transmitter may
need service. Contact Micro Motion.
Troubleshooting
Configuration and Use Manual 181