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3 Installation and Wiring
3-20
CJ-series Serial Communications Units Operation Manual for NJ-series CPU Unit(W494)
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Recommended RS-422A/485 Cable
We recommend the following wiring method to ensure transmission quality.
1
Always use shielded twisted-pair cables as communications cables.
2
Connect the shield of the communications cable to the Shell (FG) of the RS-422A/485 connec-
tor on the Serial Communications Unit. At the same time, ground the ground (GR) terminal of
the Power Supply Unit on the CPU Rack or Expansion Rack to 100
Ω
or less.
3
Always turn ON the terminating resistance at the end node of the RS-422A/485 line.
Precautions for Correct Use Precautions for Correct Use
Always ground the shield only at the Unit end. You may damage the device if you ground both
ends of the shield due to the potential difference between the ground terminals.
3-3-2 Recommended RS-422A/485 Wiring Examples
Model Manufacturer
CO-HC-ESV-3Px7/0.2 Hirakawa Hewtech Corp.
ERC RUN
RD2
SCU22
RD1
SD2
RDY
NO.
UNIT
ERH
SD1
PORT1
PORT2
0
1
23
4 56
7
89
AB
C
GR
Power Supply Unit
Ground the GR terminal to
ground the Shell (FG).
Hood and GR are
internally connected.
Ground to 100
Ω
or less.
Serial Communications Unit