Interference Suppression; Shielding; Connection Of Shielding - Bartec BAT VGA pro Manuel D'installation

Operator´s manual for BAT VGA pro
Version 1.1
3.5.4

Interference suppression

Certain basic measures must be taken to ensure freedom from interference when the display terminal are installed:
Interference voltages injected into the device via power and signal cables and static charges
caused by contact are to be conducted to earth (e.g. grounding screw terminal fixed to the
back of the device). This earthing point must be connected to the PE conductor by means of
the shortest possible low resistance copper conductor or must be integrated in the
equipotential bonding. If this point is not observed, the measures taken to suppress
interference and preclude damage to the device effectively will be impaired.
The installation point should be as far as possible away from fields of electromagnetic
interference. This is especially important if there are frequency converters in the vicinity.
Under certain circumstances it will be advisable to set up partitions to isolate the display
terminal from interference.
If inductive devices are fitted in the vicinity (e.g. contactor, relay or solenoid coils), especially
if they are powered from the same source, protective circuits (e.g. RC elements) must be
installed.
Power supply and data cables must be laid so as to avoid interference. This can, for
example, be achieved by avoiding laying such cables in close proximity to high current
carrying cables.
3.5.5

Shielding

Only cables with braided shielding should be used (recommended cover density > 80%).
Sheet shielding should not be used.
Generally, connection of the shielding at both ends results in optimum damping of all
interference frequencies.
Connection of the shielding at one side only may be more advisable if a difference in
potential exists and no equipotential bonding cable can be laid.
3.5.6

Connection of shielding

A low impedance connection to the circuit protective conductor is important to ensure a low
current fault path.
When sub-D connectors are used, the shielding should always be connected to the metal
casing of the sub-D plug.
The plug casing of some controllers is not always well connected to earth. In such cases it
may prove advantageous to insulate the shielding from the sub-D plug of the controller and
connect it directly with the protective earth conductor by means of a cable that should be
kept as short as possible (0.75 mm² ...1.5 mm²).
E_BMS00680_Rev7.doc • Operator´s manual for BAT VGA pro • Revision 7 / Status: 29. January 2004 • Technical data subject to change
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