ABB 8241, Operating Instructions Manual, Page: 5 / 28

3
3 INSTALLATION 4 ELECTRICAL CONNECTIONS
Fig. 4.1 Schematic Diagram
Computer Terminal or
Host Computer
Chain of 8240 Monitors
(Connected)
Last 8240
in Chain
Termination Resistor
(on 8240's receive input)
Observe the limitations outlined in the installation information
of the relevant Instruction Manual. The maximum serial data
transmission line length for both RS422 and RS485 systems is
1200m.
3.1 Serial Communication
Adaptors for Personal Computers
An RS422/485 communications adaptor board 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 from
cables.
3.1.1 Five-wire Configuration
The following OPTO22 boards are recommended for use with
the 4600 serial instruments:
Part No. ComputerType
AC24 XT Bus IBM PC compatible
AC24 AT AT Bus IBM PC compatible
AC34 Microchannel IBM PC.
The following ‘jumper’ selections are required on OPTO22
boards (usually supplied as the default configuration):
RX & TX install line termination jumper
Install pull-up and pull-down jumpers
CTS & RTS disable jumper installed.
Select board address and interrupts as described in the
OPTO22 manual.
3.1.2 Three-wire Configuration
The adaptor card must have the provision for disabling the
transmitter after each message is transmitted, so that bus
contention does not occur. This is often implemented by the
use of the RTS signal to control the transmitter enable. Consult
the adaptor card manufacturer to determine suitability.
Caution. Install the pull-up/pull-down resistors on
either the RX
or
TX lines. The resistors
must not
be
connected on
both
pairs of lines.
All connections, apart from those for serial data
communication, are made as shown in Figs. 2.3 and 2.5 of the
relevant Instruction Manual.
4.1 Serial Connections – Figs. 4.1 and 4.2
The transmitters must be connected in parallel as shown in the
schematic diagram – Fig. 4.1. The RS485 standard quotes
connection of maximum thirty two slaves (8240 Monitors) to
any single driver (computer terminal or host computer); the
RS422 standard quotes connection of up to ten slaves.
However, these numbers can be increased if the driver’s serial
port permits.
Make serial data connections and check the output board links
as shown in Fig. 4.2c. The type of cable used is dependent on
the transmission speed and cable length:
4.1.1 Five-wire Cable – Figs. 4.2a and 11.1
Up to 6m (all speeds)
– standard screened or twisted pair
cable.
Up to 300m
– twin twisted pair with overall foil screen and an
integral drain wire, e.g. Belden 9502 or equivalent
Up to 1200m
– twin twisted pair with separate foil screens
and integral drain wires for each pair, e.g. Belden 9729 or
equivalent
4.1.2 Three-wire Cable – Figs. 4.2b and 11.2
Up to 6m (all speeds)
– standard screened or twisted pair
cable.
Up to 1200m
– single twisted pair with overall foil screen
and integral drain wire, e.g. Belden 9501 or equivalent.