Interference Suppression; Shielding; Connection Of Shielding - Bartec POLARIS SMART HMI 17-71V6-1 Series User Manual

POLARIS SMART HMI
POLARIS Smart HMI 7" W
6.7.3

Interference suppression

6.7.4

Shielding

6.7.5

Connection of shielding

Technical data subject to change.
04/2018
- for Zone 1/21
Certain basic measures must be taken to ensure freedom from interference when the
POLARIS are installed:
- The interference voltages coupled into the device via power, data and signal line
and the electrostatic voltage caused by contact are to be dissipated through the
equipotential bonding.
- 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 will it be advisable to set up
partitions to isolate the graphic display 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 be
achieved, for example, by avoiding laying such cables in close proximity to high-
current carrying cables.
- 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.
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 to the protective earth conductor by means of a cable that should
be kept as short as possible (0.75 mm² ...1.5 mm²).
Installation
EN 31/54