VEGA FIELDBARRIER - Manual (Page 19)

FieldBarrier
Subject to reasonable modifications due to technical advances. Copyright Pepperl+Fuchs, Printed in Germany
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Following values applies especially for the FieldBarrier:
The maximum cable length per output is limited to 120 meter and may be operated
without terminators. The outputs meet the requirements of the IEC 60079-27.
5.2.4 Grounding
The cable types described in the previous section, which are recommended for both
fieldbus systems, have a shield. For reasons of EMC protection, the shield should be
grounded. There are essentially two different ways in which this is possible:
• Double-sided hard grounding of the shield (connection between the shield and po-
tential equalization
• Capacitive grounding on one end of the shield (connection of the shield to the po-
tential equalization via a capacitor) and hard grounding on the other end
• Hard grounding on one end of the shield and no grounding on the other end
The best EMC protection is achieved with grounding on both ends of the shield. In this
case, a potential equalization conductor is required.
If capacitive grounding on one end is used, there is no need for the potential equali-
zation conductor for non-Ex applications. However, the EMC protection is not as good
as when the shield is applied on both sides.
If there is a transition from the hazardous area to the safe area with capacitive ground-
ing the capacitor must meet the following requirements:
• It must have a solid dielectric, for example ceramic
• C < 10 nF
• Test voltage > 1500 V
Number of
communication members
Maximum spur length
1 device per output
1 to 12 120 m
13 to 14 90 m
15 to 18 60 m
Consider the master of the PROFIBUS Segment Coupler or the host
card at FOUNDATION Fieldbus installations as communication mem-
bers.
Use the free Segment Checker software to create topologies containing
FieldBarriers (www.segmentchecker.com).
A capacitor which meets the above requirements is integrated into each
output in the FieldBarrier. An additional capacitor is not required.