R7M-MS4
P. 6 / 7
EM-7803-Q Rev.3
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WARNINGS AND CAUTIONS WHEN LAYING CABLES
Signal cables connected to the R7M contain high-frequency components. Since these cables has the same effect as an an-
tenna, they emit these high-frequency components to the external space as noise or overlaps noise from the external space
on themselves.
Cables with shielding should be used for the signal line due to the above reason.
EMC conformance test is conducted in the condition that shielded cables and earth clamps are used with the R7M.
Warning and cautions when laying cables are stated below. These points of cautions are illustrated in the next page.
•
Use shielded cables for those signal cables installed out of the control panel and for thermocouple and RTD extension wires.
•
All the network cables connected to R7M should be shielded.
•
Use shielded cables for network communication.
•
Expose the shield at a part of the cable cover, clip it with an earth clamp, and ground it to the internal panel of the control
panel. A drain wire connected to the panel in a pig-tail form cannot maintain low impedance against high-frequency noise,
thus grounding (noise shielding) in this form will not be effective.
Supplement
:
Additional measures may be taken depending upon actual installation sites. These points of cautions are illustrated in the
next page.
•
Keep cables as short as possible. It prevents noise emissions from the cables and noise overlapping to the cables.
•
Attach a ferrite core to reduce noise impact to the signal cables susceptible to the noise. Ferrite core can be attached close
to the cable outlet of the control panel or close to the I/O terminal or connector, whichever is more effective. Also, the impact
might be reduced by winding the cable around the ferrite core for extra turns or attaching multiple ferrite cores.
•
Keep cables which are easily affected by noise away from those which can be a noise source.
Motor Drive
Cable
Power Supply
Cable
DC Signal Cable
Network Cable
Analog Signal
Cable
Often being a noise source
Often subject to noise interference.
In the following are examples of effective ways to lay cables separately:
•
Keeping physical distance (farther than 20 cm from motor drive cables, farther than 10 cm for other groups).
•
Dividing off by a grounded metal plate
•
Grouping into separate grounded metal pipes or cable shields.
Wires on each side of a filter should not be too close to each other. Noise could ride onto the other side of cable.
Extra attention needs to be paid at the following parts.
•
Noise filter that is enclosed in power cables.
•
Ferrite core that is attached to signal cables.
•
Noise limiting circuit (surge quenching circuit, transient absorber circuit, etc.) that is enclosed in signal cables.
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