PD2-6262 Helios Large Display Analog Dual-Input Rate/Totalizer Instruction Manual
17
Figure 16. 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 details.
3. Use shielded cable, twisted-pair plus ground. Connect ground shield only at one location.
Connections
Figure 17 details the wiring connections from the RS-485
connector to an RS-422/485 serial converter (such as the
PDA7485 or PDA8485) for a four-wire network.
Three Wire Connection
In order to wire the 5 pins for use as a 3-wire half-duplex RS-485 connection, it is necessary to create a
jumper connection between DI
– DO and DI- – DO- as shown below.
Figure 18. Three-Wire RS485 Connection
RS485 Connector to RS-422/485 Serial
Converter Connections
RS-422/485 Serial
Converter
PDA1485 RS-485
Adapter
DO
DI
DO
DI
DI
DO
DI
DO
Figure 17. Connections for RS485
Connector to Serial Converter
