Appendix -
Optional outputs
This appendix provides information required when an optional output is fitted to the LD4. For details
of the optional isolated & regulated transmitter supply refer to the “Electrical Installation” chapter. The three
remaining optional outputs are serial communications, analog retransmission or two extra setpoint relays.
Note that only one of these three options can be fitted at any time.
Serial communications option
Electrical connections and output board links
See diagram below. Refer to “Electrical Installation” chapter for general information on electrical
connections. External connections to the board are via plug in connectors with screw terminals these
terminals allow for wires up to 1.5mm2 to be fitted. Use twisted pair overall screened cable for RS485 and 3
core overall screened cable for RS232.
Ensure that the appropriate link is selected for RS232 or RS485. If RS232 is selected chip U1
should be in and chip U2 should be out. If RS485 is selected chip U1 should be out and chip U2 should be in.
The RS485 terminating resistor link should be in if the LD4 is the first or last unit in a RS485 chain.
Page 36 of 46
LD4LNMAN-1.0-1
GND
GND
GND
A/RX
A/RX
A/RX
B/TX
B/TX
B/TX
GND
A/RX
B/TX
SERIAL OUTPUT BOARD
SERIAL DATA
CONNECTOR
RS485 TERMINATING
RESISTOR
RS485 SELECTED
RS232 SELECTED
Computer/
PLC etc.
Computer/
PLC etc.
RS232Tx/RS485B
B
Tx
GND
GND
GND
GND
B
Rx
GND
RS232Rx/RS485A
A
Rx
A
Tx
RS485 connections
RS232 connections
LK2 LK3
LK2 LK3
LK2 LK3
RS
485
RS
485
RS
485
RS
232
RS
232
RS
232
