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(4) Cables used for the modules connected to the head module
Use shielded cables for the cables which are connected to the I/O
modules and may be extended out of the control panel.
If a shielded cable is not used or not grounded correctly, the noise
immunity will not meet the specified value.
(a) Grounding the shield of the shielded cable
POINT
Grounding with a vinyl-coated wire soldered onto the shielded section of the
shielded cable as shown below is not recommended. Doing so will raise the
high-frequency impedance, resulting in loss of the shielding effect.
• Ground the shield of the shielded cable as close to the
module as possible so that the grounded cable will not be
affected by electromagnetic induction from ungrounded
cables.
• Ground the exposed shield section in a large area on the
control panel. A clamp fitting can be used as shown below.
In this case, mask off the inner wall surface of the control
panel, which comes in contact with the fitting.
Paint mask
Shielded cable
Vinyl-coated wire
Solderless terminal
Screw
Clamp fitting
Shielded cable
45
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