BEKA BA3903 User manual

1. INTRODUCTION
The BA3903 enables an RS485-IS twisted pair bus cable to
be easily connected to, and looped-through, a device with a
standard RS485-IS port.
The BA3903 incorporates a sub D9 male connector that mates
with the standard female connector on an RS485-IS device,
such as a Pageant plug-in CPU module. The BA3903-IS
connector contains duplicate input and output screw terminals
enabling twisted pair eld wiring to be easily connected to,
and looped-through, the RS485-IS device.
The BA3903 connector also contains a switchable terminating
resistor for use at the end of an RS485-IS line.
2. RS485-IS PHYSICAL LAYER
RS485-IS is a 2-wire intrinsically safe communications standard.
The physical layer standard is summarised in the, ‘Probus
RS485-IS User and Installation Guideline’. The maximum
intrinsic safety input and output safety parameters for each
device are dened allowing up to 32 devices to be connected to
a single bus cable as shown in Fig 1. However, the maximum
current output of the eldbus isolator powering the bus cable
may restrict the number of devices that can be connected.
3. CONNECTIONS AND USE
Caution
The cover retaining screw is not captive,
neither are the two jack-screws when the
cover has been removed.
Step 1
Unscrew the back cover retaining screw and carefully lift
it off.
Instructions for BA3903
Pageant RS485-IS Connector
Issue 1
2nd September 2022
BEKA associates Ltd. Old Charlton Rd, Hitchin, Hertfordshire,
SG5 2DA, UK Tel: [phone] e-mail: [email protected]
web: www.beka.co.uk
BA3903
Hazardous areaSafe area
RS485-IS
device 2
Up to 32 RS485-IS devices
BA3903
RS485-IS
device 1
BA3903
RS485-IS
last device
BA3903
Bus out
Bus in
Bus out
Bus in
Isolator
with
RS485-IS
output
Bus in
Fig 1 RS485-IS bus topography

 Step2 Forconnectingtoaelddeviceand
  looping-throughthebus.
Sub D9
connector
Terminating resistor
not connected
A- Bus in
B+
A- Bus out
B+
A- Bus in
B+
A- Bus out
B+
When the BA3903 connector is used for connecting
the bus to a RS485-IS eld device and looping the bus
through the device, discard the plate covering the bus out
cable exit and slide the terminating resistor switch into
the not connected position. Connect the bus cable to
the appropriate in and out terminals ensuring that the two
cable retention clamps are in electrical contact with the
bus cable braid to maintain cable screen continuity.
 OR Forconnectingtothelastelddevice
Sub D9
connector
Terminating resistor connected
between input terminals
A- Bus in
B+
A- Bus out
B+
A- Bus in
B+
A- Bus out
B+
When a BA3903 is used to connect to the last
RS485-IS eld device at the end of a line, the plate
covering the bus out cable exit should be retained and
the terminating resistor switch slid into the connected
position. The bus cable should be connected to the
bus in terminals and secured with the cable retaining
clamp.
 Step3 ReassembletheBA3903connector
Ensure that the two jack-screws are correctly
positioned before retting the top cover and replacing
the securing screw.
3.1 Earthing
The screen of the RS485-IS twisted pair bus cable should
be earthed in the safe area as shown in Fig 1. If a BA3903
connector is plugged into a socket on a hazardous area
RS485-IS port which has an earthed connector shroud,
care should be taken to avoid circulating currents.
Ideally each intrinsically safe circuit should only have a
single earth connection in the safe area. Multiple earth
connections should be connected to the plant’s potential
equalising conductor.
4. MAINTENANCE
Pageant BA3903 connectors should be regularly inspected
to ensure that they have not been damaged. The frequency
of inspection depends upon environmental conditions.
Noattemptshouldbemadetorepairafaulty
BA3903Connector.  Suspect Connectors
shouldbereturnedto BEKA associates or
yourlocalBEKAagent.
5. GUARANTEE
Connectors which fail within the guarantee period should
be returned to BEKA associates or your local BEKA agent.
It is helpful if a brief description of the fault symptom(s) is
provided.
6. CUSTOMER COMMENTS
BEKA associates are always pleased to receive comments
from customers about our products and services. All
communications are acknowledged and whenever
possible, suggestions are implemented.
2
Old Charlton Rd, Hitchin, Hertfordshire, SG5 2DA, UK
Tel: [phone] e-mail: [email protected]
web: www.beka.co.uk
All associated manuals, certificates, and
datasheets can be downloaded from
https://www.beka.co.uk/qr-ba3903_1