14 Rockwell Automation Publication 1719-IN001D-EN-E - November 2020
1719 Ex I/O Installation Instructions
Twisted-pair cables significantly reduce the influence of these interference fields, particularly when compared to cables with parallel strands. The direction of the recorded
interference field in a twisted-pair cable reverses over short intervals. This means that the induced interference is practically canceled out, while in parallel strands the
interference is active across the entire area.
Shielding keeps interfering signals away from the communication path.
EMC filters are used in many devices to divert any interference to ground. For the sake of symmetry, all lines are provided with suitable capacitance. Capacitively coupled
high frequency interference is effectively canceled out by the symmetrical layout.
The same applies to galvanically isolated signals. However, unexpected results may arise in networks that are created by multichannel systems without isolation. This is
because the filter capacitors may even run in parallel, depending on the setup. Isolate the channels to eliminate any interference.
Reduced admission of interfering signals in twisted-pair cable
Shielding prevents the entry of interference fields
EMC filters in signal paths
EMC filters in a network (simplified diagram)
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