
CE Conformity, Directives and Standards
KeTop T50VGA
152
User's Manual, Version: 1.3
© KEBA 2007
Coupling paths very often consist of two or more parallel lines running
closely together. The coupling is a field coupling that takes place at low fre-
quencies either via the electrical field (capacitive coupling) or via the mag-
netic field (inductive coupling).
At high frequencies and with corresponding expansion of the parallel run-
ning lines one speaks about an electromagnetic coupling due to close link-
ing of both field types.
Direct coupling can occur when electrical circuits from the interference
source and electrical circuits from the interference sink have common line
components.
If there is a large distance between an interference source and an interfer-
ence sink then one speaks of a radiation coupling.
14.3.2 EMC measures
In principle, all devices should be designed in such a way as to function re-
liably in the planned environment and in doing so should not interfere with
other systems. All products of the Kemro product range (K2 control sys-
tems and KeTop) meet these requirements and it is not necessary to use
any of the EMC measures described below when the specified additional
units, cables and wiring are used.
However, additional EMC measures may be necessary for various reasons.
The following text is designed to help the user to correctly implement any
additional EMC measures.
14.3.2.1 Shielding
Electromagnetic emission problems and immunity problems often occur in
products at the same time. Likewise, EMC measures are mostly effective in
the case of both emission problems and immunity problems.
Shielding fulfils two main tasks. On the one hand, the penetration of elec-
tromagnetic fields into sensitive electronic parts is prevented and, on the
other hand, the radiation of electromagnetic fields is also prevented.
A complete EMC shield consists of a shielded housing, which protects the
sensitive electronics and prevents them from transmitting interference, and
cable shields that shield the sensitive interface signals and prevent the de-
vice from transmitting interference via its interfaces.
The cable shield basically connects two shielded housings together and
must therefore be connected directly to the shielded housings of the sensi-
tive electronics (connection points).
Particular attention should be paid to the connection between the cable
shield and the shielded housings of the device. In order that the shield ef-
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