A-7
Appendices
NB-series Programmable Terminals Setup Manual(V107)
A-3 RS-422A/485 Connections
App
A-3-1 Grounding and Shielding of the Cables
A-3 RS-422A/485 Connections
When performing communications using RS-422A/485, carry out the connections, shielding and
grounding as follows:
Grounding wiring
The NB Unit has a functional grounding terminal (FG: ).
(1) Generally, make the grounding according to Fig. (a).
• Connect the grounding terminals (GR) of the devices and the functional grounding terminal
( ), at only one point make a D-type grounding (Max. grounding resistance 100Ω).
• Short-circuit the LG terminal and GR terminal of the PLC.
• Use a cable with a minimum of 2 mm
2
for the grounding cable.
• For details about the connection methods, refer to the related communication Unit
manuals.
(2) As shown in Fig. (b), when the NB Unit, and noise source equipments such as motors and
inverters, etc. are installed on the same panel, do not ground the NB Unit’s functional
grounding terminal ( ).
Shielding of RS-422A/485 Cables
Be sure to shield the RS-422A/485 cables. Connect the grounding terminals (GR) of the devices and
the functional grounding terminals ( ), at only one point make a D-type grounding (Max. grounding
resistance 100Ω), carry out a single-end shielding according to Fig. (a).
If grounding is not done to the functional grounding terminal ( ) of the NB Unit, shield both ends as
shown in Fig. (b).
Note In order to avoid malfunctions caused by interferences, shield the cables properly.
A-3-1 Grounding and Shielding of the Cables
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