Omron NA5-12W series, Hardware User Manual

Page: 78 / 156

3 Installation and Wiring
3 - 20 NA-series Programmable Terminal Hardware User’s Manual (V117)

Precautions when Grounding
• If the same ground is used for both the signal lines and the enclosure, isolate the channel base (a
grounded metal plate inside a control panel) with an insulating material.
• To prevent influence from leakage current from other electrical devices, electrically isolate the panel
in which the NA Unit is housed from other devices.
• If high-frequency equipment is present, then ground not only the high-frequency equipment but also
the panel itself in which the NA Unit is housed.
 NA Unit Functional Ground Terminal
The NA Unit has the following ground terminal.
Functional ground terminal: Connected to a neutral point in the noise filter to provide a ground when
power supply noise causes malfunctioning.
When the functional ground terminal is correctly grounded, it is generally effective in suppressing power
supply common noise. Occasionally, however, grounding this terminal will result in picking up more
noise, so be careful when using it.
Connections When Using an External Noise Filter
Other
device
Other
device
(c) Independent grounds:
Incorrect
(a) One-point grounding:
Acceptable
(b) Common ground:
Incorrect
Other
device
NA Unit NA Unit NA Unit
Ground of
100 Ω or
less
Insulating material
Channel base
The NA Units are designed to be
mounted so that they are isolated
(separated) from the mounting surface
to protect them from the effects of noise
in the installation environment (e.g., the
environment in which the control panel
is mounted).
Independent ground
External power
supply side
NA Unit side