Sysmac OMRON NA Series, User Manual

Page: 80 / 182

3 Installation and Wiring
3 - 20 NA-series Programmable Terminal Hardware User’s Manual (V117)
Grounding has the following two purposes.
• Protective Grounding
Protective grounding is done to ensure safety. It is intended to prevent electrical shock by holding the
electrical potential at the grounding potential that is generated by factors such as leakage, induction,
or failure.
• Functional Grounding
Functional grounding is done to protect device and system functions, including prevention of noise
from external sources, or prevention of noise from devices or equipment that could have harmful
effects on other devices or equipment.
The functional ground must in some cases be determined by experimentation. It is important to suffi-
ciently check the particular circumstances before grounding.
 Principles of One-point Grounding
For devices to operate properly, the reference potential between the devices must be stabilized. Use
one-point grounding so that noise current does not flow to ground lines between the devices.
• Use one-point grounding as shown in figure (a). Connect to the ground pole of the other devices.
• Never connect to the same ground as a device that draws a large amount of power, such as a
motor or inverter. Ground the devices separately to avoid mutually adverse influences.
• To prevent electrical shock, do not connect to ground poles (or steel frames) to which multiple
devices are connected.
• Use a ground pole as close to the NA Unit as possible and keep the ground line as short as possi-
ble.
3-5-6 Grounding
Grounding Methods and Precautions
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