ABB C1900 Series, Installation Manual

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2
2.1 Selection of Serial Communication Adaptors for Personal Computers
Information.
• A RS422/485 communication board is required in the host PC.
• Observe the limitations outlined in the Installation Guide – the maximum serial data transmission line length for both
RS422 and RS485 systems is 1200m.
An RS422/485 communications adaptor is required for serial links. It is strongly recommended that the card used has galvanic
isolation
to protect the computer from lightning damage and increase immunity from noise pick-up.
2.2 Recommended OPTO22 Boards
The following OPTO22 boards are recommended for use with the COMMANDER 1900 Series of instruments:
Part No. Computer Type
AC24 AT AT Bus IBM PC compatible
AC34 Microchannel IBM PC
2.3 Pull-up and Pull-down Resistors – Figs. 2.1 and 2.2
To prevent false triggering of the slave (COMMANDER 1900) by the presence of noise when the master (host computer) is
inactive, 1.8K pull-up and pull-down resistors must be fitted to the RS422/485 adaptor card – see Figs. 2.1 and 2.2.
2 ELECTRICAL INSTALLATION
Fig. 2.1 Pull-up and Pull-down Resistors (3-wire Operation)
Tx+
Tx–
GND
+5V
0V
Computer Terminal or Host Computer
Rx–
Rx+
Tx–
Tx+
'A'
'B'
1
2
7
8
9
3
4
5
6
Serial Module
Terminal Board
COMMANDER 1900
Pull-up and Pull-down Resistors
+5V
1.8k
Ω
Pull-up Resistor
1.8k
Ω
Pull-down Resistor
'A'
'B'
5 8
6
7
3 10
4 9
Linked In Linked Out
+5V
0V
1.8k
Ω
Pull-up
Resistor
1.8k
Ω
Pull-down
Resistor
'A'
'B'
'A'
'B'
Links on Serial Module
Tx+/Rx+
Tx–/Rx–
PL2 PL2
GND
Note . If an RS422/485 adaptor card without pull-up and pull-down
resistors is used, the COMMANDER 1900's internal resistors can be
linked in.