Noise Intrusion

Verify how error occurrence condition changes while taking the following countermeasures.

• Ground of FG (DRAIN) wire
  Normal Grounding: Ground the DeviceNet network at only one point.
  

  • Countermeasure 1: Disconnect the wire between V- and FG.
    Disconnect the wire between V- and FG when you cannot ground the FG wire.
    

  • Countermeasure 2: Disconnect the shield wire to isolate it from the ground.
    When noise intrudes the ground line due to a noise source such as an inverter installed near the communications power supply, disconnect the shield wire of the communication cable and isolate it from the ground to restrain noise intrusion.

• 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.
  
  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.

• Communications power supply
  When sharing the communications power supply with I/O devices, provide power sources separately.
  Separating power source prevents noise caused by I/O device operations from affecting communication.
  

  Symbol	Description
  a	Communications power supply 24 V
  b	Disconnect I/O devices from the communications power supply.
  c	Power Supply Tap