User`s guide

44 MLS User’s Guide
Installation
NOTE
Connect the shields to earth ground only at the
computer or other 485 interface. Do not connect
the shield at the MLS. Connect a 200 ohm termi-
nating resistor between RX- and RX+ at the last
MLS (Ju3).
The loop resistance of the transmission line (wire
only, not terminating resistor) must not exceed 200
ohms.
This table shows RS-485 connections.
EIA Standard RS-485 specifies the electrical characteristics of
transmitters and receivers for digital multi-point systems. Watlow-
Anafaze equipment meets RS-485 and RS-422 standards. However, RS-
485 does not specify transmission lines, signaling rates, protocols, etc.
Watlow-Anafaze recommends the following:
•
Maximum signaling rate: 9600 baud.
•
Twisted shielded pairs for the RS-485 cables.
Line RS-485 Connection Color
TXB RX+Pin 1 Blue/White
TXA RX-Pin 3 Red
RXB TX+Pin 5 Yellow
RXA TX-Pin 2 Black
Ground Pin 4 Green
Shield Shield Pin 6
(Not jumpered internally)
TXA
TXB
RXA
RXB
Ground
Black Box
LD 485
A
RX+ #3
RX- #1
TX+ #2
TX- #5
#6
MLS T3A/B
[1] RJ12
RX+ #3
RX- #1
TX+ #2
TX- #5
#6
MLS T3A/B
[n] RJ12
Red
Black
Yellow
Silver
Blue/White
Red
Black
Yellow
Silver
Blue/White
200
Ω