Appendix
A.2 Protection against electromagnetic interference
S7-300, CPU 31xC and CPU 31x: Installation
A-6 Operating Instructions, Edition 08/2004, A5E00105492-05
A.2.2.3 3. Basic rule for ensuring EMC
Rule 3: Fixing the cable shielding
Ensure proper fixation of the cable shielding.
• 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 conductor bar and the
cabinet/enclosure must be of a low impedance.
• Always install shielded data cables in metal/metallized connector housings.
See also
Cable shielding (Page A-12)
A.2.2.4 4. Basic rule for ensuring EMC
Rule 4: Special EMC measures
Take special EMC measures for particular applications.
• 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.
See also
How to protect digital output modules against inductive surge voltage (Page A-28)
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