Emerson Network Router User Manual
Page 20
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.