Omron OMNUC W R88A-NCW152-DRT, Руководство пользователя

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6 DeviceNet Communications
6.3.2 Communications Line Noise Precautions
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6
6.3.2 Communications Line Noise Precautions
This section describes network grounding methods, noise countermeasures for communica-
tions lines, and noise countermeasures according to wiring methods.
„ Communications Line Noise
The communications line sends and receives high-speed pulse signals, and checks whether
the data is correct by checking the sequence of the signals. If the amount of noise on the
communications line is too great, the interference will alter the communications signal data,
and communications will be impossible. Communications lines are more sensitive and
require faster response than normal I/O lines, so be sure that noise does not interfere with
communications. Use the preventative noise countermeasures described below when config-
uring the system to ensure smooth system start up.
„ Grounding the Network
Network grounding method and ground line are described below.
Method
The DeviceNet network must be grounded at one location only so that a ground loop is not
created. The ground should also be connected as close as possible to the center of the Net-
work. Connect the cable shield to the ground terminal on the communications power supply
and then connect to a ground of 100
Ω
max., as shown in the following diagrams.
Note
If more than one communications power supply is connected to the
same network, ground only the one nearest the center of the network.
Do not connect the shield wire at the other power supplies.
Note 1. Always ground the communications cable shield directly at one location only in the network.
2. Always ground to 100
Ω
or less.
3. Always use a separate ground. Never use the same ground as for inverters or other drive system
devices.
Power Supply Tap
V+
CAN H
Shield
CAN L
V-
V+
CAN H
CAN L
V-
V+ V- Ground terminal
FG V+ V-
Communications
power supply
Ground (100
Ω
max.)
DeviceNet
special cable
Shield