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32 ProLink
®
II Software for Micro Motion
®
Transmitters
Installation and Setup
8. Try adding resistance to the connection.
• For HART connections, refer to the installation instructions earlier in this chapter. Verify
that there is a 250–600 Ω resistor in parallel in the communications circuit.
• For HART connections to Model 1700/2700 transmitters with the intrinsically safe outputs
option board, ensure that the resistor is in series. Attach the modem across the resistor.
• RS-485 connections may require added resistance if the connection is long-distance or if
there is external noise that interferes with the signal. Add two 120-Ω resistors in parallel
with the output, one at each end of the communication segment.
9. For RS-485 connections, swap the leads between the two terminals and try again.
10. For Modbus network connections, ensure that ProLink II is the only Modbus master active on
the network.
11. For RS-485 connections, try connecting through the service port, if available on your
transmitter.
12. For HART/Bell 202 connections:
a. If burst mode in enabled, try disabling it.
b. Ensure that polling for external pressure/temperature is disabled.
c. Ensure that ProLink II is the only master on the network.
13. For HART connections using the VIATOR USB HART Interface:
a. Ensure that you have checked the box labeled
Converter Toggles RTS in the ProLink II
Connect window.
b. Ensure that the required Windows driver is installed on your PC. If this driver is not
installed, Windows will not recognize the USB converter when it is plugged into the USB
port.
14. For connections to the Model 2400S transmitter, if you are using Modbus ASCII protocol with
an RS-485 connection rather than a service port connection, ensure that Modbus ASCII
support is enabled on your transmitter.