Western Reserve Controls, Inc.
1782-JDO User’s Manual
PRELIMINARY
17
Figure 4-2
DeviceNet cable connector
4.4.3 RS485 Network Termination (1782-JDO-2)
It is common practice to terminate an RS485 network system
at each end of the serial
cable
to eliminate electrical reflections. An appropriate value for the terminating resistor
typically is:
•
100-120 ohm, depending upon the characteristic impedance of the cable used
o
121 ohms (same value as the DeviceNet terminator) is a standard resistor value
that may be used in many cases
•
1% metal film
•
1/4 Watt
Correct cable termination is the responsibility of the user. The 1782-JDO-2 does not include
an internal terminating resistor.