Serial Communication Converters & Adapters Instruction Manual
11
PDA7422 Trident RS-485
Serial Adapter
Description
The PDA7422 converts the serial output of the
PD765 Trident meter to balanced, full or half-
duplex RS-485 signals.
The PD7422 has a removable screw terminal
connector for the 485 terminals which includes
Transmit Data (DO) and (/DO), Receive Data
(DI) and (/DI), and Signal Ground.
Baud rates are adjustable and handled by the
PD765 (see the Trident Instruction Manual for
more details).
The PDA7422 has three diagnostic LEDs: a
Power (P) LED to show when the adapter is
powered properly, a Transmit Data (TX) LED to
show when the adapter is sending data out from
the PC side, and a Receive Data (RX) LED to
show when the adapter is receiving data from
the Trident PD765 meter.
Installation
Figure 9 shows the connection of a Trident
meter to a PC using the PDA7422 serial adapter
and a PDA7485 RS-232 to RS-422/485
converter in an RS-422 network. The PDA7422
has an RJ11 connector to connect the PDA7420
modular cable and a screw terminal connector to
connect to the RS-422 network. Figure 10
shows the connection of several Trident meters
with PDA7422 serial adapters to a PC using a
PDA7485 RS-232 to RS-422/485 converter in an
RS-485 network.
PD765 Serial Communication
Address (
serl
)
When using more than one meter in a multi-drop
or multi-point mode, each meter must be
provided with its own unique address. For the
PD765 Trident meter the address may be
programmed from 00 to 99 for PDC Protocol and
from 1 to 247 for Modbus RTU. The PD765
Trident meter is factory set to PDC Protocol at
address 00.
To change the PD765 Trident meter address:
1. Press and hold
Right
arrow and
Menu
buttons for three seconds to access
Advanced Features menu of the meter.
2. Press
Up
arrow until Serial (
SErL
) menu
is displayed and press
Enter/Ack
,
Addr
is displayed.
3. Press
Enter/Ack
to change meter
address using
Right
and
Up
arrow
buttons. Press
Enter/Ack
to accept.
4. Press
Menu
button to exit and return to
Run Mode.
Figure 9. RS-422 or RS-485 Wiring
Notes:
1. Termination resistors are optional and
values depend on the cable length and
characteristic impedance. Consult the
cable manufacturer for
recommendations.
2. Refer to RS-232 to RS-422/485
Converter documentation for further
details.
3. Use shielded cable, twisted-pairs plus
ground. Connect ground shield only at
one location.
