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Chapter 6
Wiring digital communications
Topics covered in this chapter:
Wire the transmitter to an RS-485 multidrop network
Prerequisites
Use twisted-pair, shielded cable that consists of 24 AWG (0.25 mm
2
) or larger wire between the 9739 MVD transmitter and
the RS-485 communication device. Maximum cable length is 4000 ft (1200 m).
Note
For long-distance communication, or if noise from an external source interferes with the signal, install a 120-Ω, 1/2-W
resistor at both ends of the network cable to reduce electrical reflections.
resistor at both ends of the network cable to reduce electrical reflections.
Procedure
Use terminals 27 and 26 to wire the 9739 MVD transmitter to an RS-485 network.
Important
The Service port clips on the user interface of the 9739 MVD transmitter are directly connected to RS-485 terminals
(26 and 27). If you wire the transmitter for RS-485 digital communications, you cannot use the Service port clips for
communication with the transmitter.
(26 and 27). If you wire the transmitter for RS-485 digital communications, you cannot use the Service port clips for
communication with the transmitter.
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Micro Motion 9739 MVD Transmitters