Helios PD2-6400 High Voltage & High Current Meter
Instruction Manual
19
RS-485 Connection Examples
Figure 23. Five-Wire RS-485 Connections
Figure 24. Three-Wire RS-485 Multi-Drop
Connections
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
RS-485 Converter Connections
below details the wiring connections from
the RS-485 connector to an RS-485 serial converter
(such as the PDA7485-I or PDA8485-I) for a five-wire
network.
RS-485 Connector to RS-485
Serial Converter Connections
RS-485 Connector
RS-485 to USB or
RS-232 Converter
DO
DI
DO
DI
DI
DO
DI
DO
Figure 25. Connections for RS-485 Connector to
Serial Converter
Three-Wire Connection
In order to wire the five pins for use as a three-wire
half-duplex RS-485 connection, it is necessary to
create a jumper connection between DI to DO and /DI
to /DO- as shown below.
Figure 26. Three-Wire RS-485 Connection
Digital I/O Connections
Digital inputs and outputs are provided in order to
expand the functionality of the meter. Digital input
connections are made via a push button or switch to
the appropriate digital input terminal and the +5 VDC
terminal. Digital output connections are made by
wiring from the appropriate digital output terminal to
the ground terminal.
Figure 27. Digital Input and Output Connections
Shield
RS-232 Serial
Connection
to PC
R
R
Twisted-Pair
R
DI
DI DO DO
__ __
RS-232 to RS-485
Converter
DI
DI
DO
DO
R
Shield
Twisted-Pair
R
Meter #1
DI
DI DO DO
__ __
DI
DI DO DO
__ __
Last Meter
RS-232 Serial
Connection
to PC
R
RS-232 to RS-485
Converter
DI
DI
DO
DO
__ __
DI
DI DO DO
O1 O2 O3 O4 G
I
1
I
2
I
3
I
4
+5
Ground
5 VDC
