Serial Communication Converters & Adapters Instruction Manual
27
PDA7485
RS-232 to RS-485
Converter
RS-232 Serial
Connections
to PC
Last Adapter
R
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
PR
EC
IS
IO
N
D
IG
IT
A
L
PR
EC
IS
IO
N
D
IG
IT
A
L
Figure 10. 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 RS-232 to RS-485 Converter documentation for further de-
tails.
3.
Use shielded cable, twisted-pair plus ground. Connect ground shield
only at one location.
