Emerson Network Router User Manual page 20

Installation and Setup
Figure 2-5 Model 1700/2700 I.S. transmitters: Resistance and voltage requirements for
HART/Bell 202 connections
1000
900
800
700
600
500
400
300
200
100
0
12
Figure 2-6 HART/RS-485 connection to transmitter or multidrop network
DCS or
PLC
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.
14
A minimum of 250 ohms and 17.5 volts is required
14 16 18
Supply voltage VDC (Volts)
R1
Attach serial port or USB
adapter if necessary (not
shown)
R = (V – 12)/0.023
max supply
20 22 24
RS-232 <-> 2-wire RS-485
interface converter
ProLink
Operating range
26 28
RS-485 terminals
Transmitter
®
II Software for Micro Motion
30
®
Transmitters