User Manual

7000 Bus Converter User’s Manual (Version 1.8 Jan/2006, 7PH-006-18) --------------- 68
For example, the q7510, s7510 are used to isolate local modules
from nRS-485 network. If there is high energy transient on nRS-485
network, all the local modules will be safe.
Isolation Configuration (Strongly Recommended):
If the RS-485 network is not over 100 meters, the terminated
resistors are not needed. However, it may be necessary to insert two
terminated resistors at both end of the RS-485 segment. It is not easy to
calculate the value of a terminator resistor. The best way to do this is to
use an oscilloscope to check the RS-485 signal directly. If the impedance
match of RS-485 network is OK, the oscilloscope will show a very nice
square wave. If these square wave signals are distorted, the user will
need to insert two terminators at both end of the RS-485 segment.
OK
Resistor value of
terminator is too small
Resistor value of
terminator is too big