Cables - Mitsubishi Electric MELSEC-Q Series User Manual

3.1.3

Cables

The cables extracted from the control panel contain a high frequency
noise component. On the outside of the control panel, therefore, they
serve as antennas to emit noise. To prevent noise emission, use
shielded cables for the cables which are connected to the I/O modules
and intelligent function modules and may be extracted to the outside of
the control panel.
The use of a shielded cable also increases noise resistance.
The signal lines (including common line) of the programmable
controller, which are connected to I/O modules, intelligent function
modules and/or extension cables, have noise durability in the condition
of grounding their shields by using the shielded cables. If a shielded
cable is not used or not grounded correctly, the noise resistance will not
meet the specified requirements.
(1) Shield grounding
(a) When grounding the shied, position the grounding point closer
to the module and take care so that the electromagnetic
induction will not occur between the grounded cable and
ungrounded one.
(b) When grounding the shield, strip a part of the outer insulation
layer to expose the shield, and make the shield contact with
the control panel in the largest area as possible. The clamp
fitting as shown below can be used. In this case, however, the
contact area on the panel's inner surface must be masked
during painting.
Note) The method of earthing by soldering a wire onto the shield section of
the shielded cable as shown below is not recommended. The high
frequency impedance will increase and the shield will be ineffective.
Shield section
Shielded cable
Wire
Crimp terminal
13
Paint mask
Screw
Clamp fitting
Shielded cable