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Emerson Network Router User Manual

Page 20

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14

ProLink

®

II Software for Micro Motion

®

Transmitters

Installation and Setup

Figure 2-5

Model 1700/2700 I.S. transmitters: Resistance and voltage requirements for
HART/Bell 202 connections

Figure 2-6

HART/RS-485 connection to transmitter or multidrop network

R

max

= (V

supply

– 12)/0.023

A minimum of 250 ohms and 17.5 volts is required

Supply voltage VDC (Volts)

Exte

rn

al resistance (Ohms)

Operating range

12

30

14

16

18

20

22

24

26

28

0

1000

900

800

700

600

500

400

300

200

100

DCS or

PLC

R1

Attach serial port or USB
adapter if necessary (not
shown)

RS-485 terminals

Transmitter

RS-232 <-> 2-wire RS-485
interface converter

Notes:
• Connect the interface leads to the RS-485 terminals on the transmitter, or to any point on the network.
• Ensure that your transmitter’s RS-485 terminals are configured for HART protocol.
• For RFT9712 transmitters, set the jumper for RS-485 communications.
• For long-distance communication, or if noise from an external source interferes with the signal, add two 120-

Ω

terminating resistors (R1) at each end of the RS-485 network.