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4. Troubleshooting (DeviceNet)
Countermeasure 2: Disconnect the shield wire to isolate it from the ground.
When noise intrudes the ground line because a noise source such as an inverter is
installed near the communications power supply, disconnect the shield wire of the
communication cable and isolate it from the ground to restrain noise intrusion.
Power Supply Tap
V+
CAN H
Shield (S)
CAN L
V-
V+
CAN H
Shield (S)
CAN L
V-
V+ V- S
V+ V- FG
Communications
Power Supply
24 V DC
Ground 100
Ω or less.
DeviceNet cable
Disconnect here.
♦ Induced noise via communication cable
Separate the DeviceNet signal wire from the other wires (especially power wires).
* Separate the signal wire from the power wires 300 mm or more.
Light electrical cable
Communication cable
Control cable
Power cable
Signal wire
PLC in
p
ut/out
p
ut wire
PLC power wire
Control circuit wire
Power wire
Suspended ducts
Floor ducts
1
2
12
1 2
1 Signal wire
PLC input/output wire
2 Power wire
300 mm
or more
Conduit
300 mm
or more
During site inspection, bypass the wire that is possibly affected by induced noise with other
cables and then lay the cables. Establish the communication under no induced noise
condition and verify whether an error occurs.
102 Fieldbus I/O Rev.6