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When connecting to a PLC (RS-485)
(Fig. 12.2-3)
Shielded wire
Connect only one side of the shielded wire to the FG terminal so that current cannot flow to the shielded
wire. If both sides of the shielded wire are connected to the FG terminal, the circuit will be closed
between the shielded wire and the ground. As a result, current will run through the shielded wire and this
may cause noise.
Be sure to ground the FG terminal.
Terminator (Terminal resistor)
Do not connect a terminator with the communication line because each KT4H/B has built-in pull-up
and pull-down resistors instead of a terminator.
Even though a terminator is not necessary for communication between the PLC and KT4H/B, if a
terminator is required due to signal reflection, connect the terminator on the PLC side.
Connect a terminator of 120 or more resistance.
Shielded wire
KT4H/B
FG
FG
PLC
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