RS485 CONNECTIONS
RS485 is a half duplex serial communications link and is the
standard most commonly used for industrial applications due
to it’s high noise immunity and multi-drop capability. It
enables a PC to communicate with up to 128 instruments
over distances up to 1200 metres, and requires the addition
of an RS485 interface card, or a separate RS232 / 485
converter.
Installation / Cabling
RS232 CONNECTIONS
RS232 is the standard most widely used for interfacing
peripherals to PC’s and is designed for serial communications
with single instrument up to distances of 15 metres, in a low
electrical noise environment.
Connection is via a screened two core cable where the
voltage signal on each line is referenced to the screen which
is grounded. Most PC’s have one or two RS232 compatible
ports fitted as standard.
4
1
2
3
4
5
6
7
8
9
10
11 12
13
14
15
16
3300/9300
rear terminal
1
5
6
9
PC Com Port
DB-9 Pin
Tx
Rx
Gnd
Tx Rx (+)
1
2
3
4
5
6
7
8
9
10
11 12
13
14
15
16
To
additional
units
1
2
3
4
5
6
7
8
9
10
11 12
13
14
15
16
3300/9300
unit 2
Tx Rx (-)
3300/9300
unit 1
Gnd
Tx Rx (+)
Tx Rx (-)
Gnd
Connections if PC 485 card used
To
RS 485
interface
Diagram 2
Diagram 3
