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S7-300 Automation System, Hardware and Installation: CPU 31xC and CPU 31x
12-6 A5E00105492-03
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Take care that all cable shielding is properly fastened (refer to the section on
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• Always use shielded data cable. Always connect both ends of the shielding to
ground on a large area.
• Analog cables must always be shielded. For the transmission of low-amplitude
signals it might prove to be more efficient to have only one side of the shielding
connected to ground.
• Directly behind the cable entry in the cabinet or enclosure, terminate the
shielding on a large area of the shielding/protective ground bar and fasten it
with the help of a cable clamp. Then, route the cable to the module; however,
do not connect the shielding once again to ground in this place.
• Connections between the shielding/protective ground busbar and the
cabinet/enclosure must be of a low impedance.
• Always install shielded data cables in metal/metallized connector housings.
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Some special applications might require special EMC measures (refer to the
section on +RZWRSURWHFWGLJLWDORXWSXWPRGXOHVDJDLQVWLQGXFWLYHVXUJHYROWDJH).
• Connect anti-surge elements to all inductive devices not controlled by S7-300
modules.
• For cabinet or cubicle lighting in the immediate range of your controller, use
incandescent lamps or interference suppressed fluorescent lamps .
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Create a homogeneous reference potential and ground electrical equipment
whenever possible (refer to the section on (TXLSRWHQWLDOERQGLQJ).
• Route your equipotential conductors over a wide area if potential differences
exist or are expected between your system components.
• Make sure you carefully direct your grounding measures. Grounding measures
protect the controller and its functions.
Form a star circuit to connect the equipment in your system and the cabinets
containing central/expansion units to the grounding/protective conductor system.
This prevents the formation of ground loops.
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