Serial Communication Converters & Adapters Instruction Manual
42
Figure 26 shows an example configuration of a two-wire network. Each
device (e.g. Trident PD765 meter) connected to the same network must
have a unique address.
PDA8485
USB to RS-422/485
Converter
USB
Connection
to PC
Last Adapter
R
R = 120 Ohm termination resistor, typical
Shield
Twisted-Pair
R
DI
DI DO DO
DI
DI DO DO
Modular Cable to
Meter
(Provided)
Adapter #1
PDA7422
RS-422/485
Adapter
DI
DI
DO
DO
P
RE
C
IS
IO
N
D
IG
IT
A
L
PR
EC
IS
IO
N
D
IG
IT
A
L
Figure 26. RS-485 Two-Wire Multi-Drop 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 PDA7422 documentation for further details.
3.
Use shielded cable, twisted-pair plus ground. Connect ground shield
only at one location.
