EMC-compliant installation

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HMIs, human machine interfacesPanel PC ET/MT-4x6...Electrical InstallationInterference suppression measures / Installation guidelinesEMC-compliant installation


The use of interference-protected cables and their screen connection is another important measure.


Connection of cable shield:



In non-hazardous areas, a double-sided shield connection should be used between the controller and communication module for the data cable.

Generally, connecting the shield at both ends is the only way to achieve optimum reduction of all interference frequencies!



Shields for data cables used in hazardous areas should be connected to the potential equalization on one side and with the lowest possible impedance in the non-hazardous area (see installation example diagram in the chapter entitled "Eqipotential bonding and cable shields").



Alternative ways to connect the cable shield are available for EMC interference, but they must conform to national installation directives.



Connection of cable shield:


In order that interference currents coupled into the cable shield do not themselves become sources of interference, there must be a low-impedance connection to the protective earth or the equipotential bonding.


When using sub-D plug connectors you should always connect the screen to the metallic or metal-plated connector casing. Do not connect the shield to pin 1 on the plug connector!


The plug terminal of some controllers is not always properly earthed. In such cases it may prove useful to isolate the cable shield from the sub-D connector of the PLC and connect it directly to the earth lead or functional earth by means of a preferably short cable (0.75 mm²...1.5mm²).


With stationary operation we recommend that the shielded cable be stripped fully and connected to the earth rail or equipotential bonding.



In this case the shield end at the interface should not be reconnected!


When shielding in this way use metal cable clips which have a large connection area to the shielding surface and make good contact.



See also:

Kapitelseite Interference suppression measures / Installation guidelines

Kapitelseite Equipotential bonding and shielding



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