power automation PA 8000 LW Series, Installation Instructions Manual, Page: 90 / 132

Electrical, magnetic and electromagnetic interference fields are weak-
ened by means of shielding
Via the shielding rail, which is connected with low impedance to the
rack, interference currents are shorted by the cable shield to the
ground. It's important that the connection to the protected ground con-
ductor is impedance-low, because otherwise the interference currents
may cause interference.
For the use of shielded cables the following rules are important:
n The screen cover should be higher than 80%
n The cables have a copper braid (shield / screen)
n Normally the cable shield must be connected to ground in both
sides of the cable. Double-sided grounding is necessary to achieve
high-quality interference suppression in the higher frequency
range. The cable shield can be connected to single-sided
grounding in exceptional cases, but if that is done, only lower fre-
quencies will be absorped.
A single-sided ground connection of the cable shield may be con-
venient, if:
–
the conduction of a potential compensating line is not possible
– analog signals (some mV respectively μA) are transferred
– foil screens (static screens) are used instead of screens made
of copper braid.
n When using data lines always use metallic or metallized plugs for
serial couplings. Fix the cable screen of the data line at the plug
rack.
n It is convenient to strip the insulated cable interruption free and lay
it on the isolation/protected ground conductor line (stationary oper-
ation).
n Metal cable clamps to fix the cable shield have to be used. The
clamps must clasp the copper braid extensively and have good
contact.
n The cable shield has to be laid on a protective earth rail directly
after the entry of the cable in the cabinet. Do not attach the cable
shield again on the CNC control / PAMIO device.
Please observe at installation!
At potential differences between the grounding points, there may
be a compensation current via the cable shield grounded at both
sides.
Shielding Of Conductors
L CAUTION
PA 8000 LW CNC control unit
Technical data
25.09.2015 | 90