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1.4 Channel Structure
Each Channel is electrically isolated and internally connected to the transparent intelligent backbone. The
termination is switchable and powered by the ProfiHub. The shielding of the PROFIBUS cable can be directly
grounded or indirectly grounded (see the next paragraph).
RX-OK
ERROR
Intelligent
Backbone
Fig. 5 - Channel structure
1.5 Grounding System
The ProfiHub B2FOR+ / B4FOR+ can be grounded by 3 methods:
1. Direct grounding on the Ground Rail
2. Indirect grounding (through a capacitor)
3. Combination of direct and indirect.
The power supply must be grounded directly on the Ground Rail. The shielding of the PROFIBUS cables can be
directly or indirectly grounded. If you do not want to ground all or some cables to the common ground, i.e.
compensating current, the cable shielding must be connected to pin 'I' which stands for Indirect grounding. A
capacitor with a parallel high value resistor will separate the 2 potentials (
signal against non-DC disturbances.
If the ground is accidentally connected to the indirect ground on a channel, the connection to the Direct
Grounding bypasses the capacitor of the Indirect Ground connection. The current on the shield will flow to
Direct Ground.
1.6 Cable lengths for PROFIBUS DP
The cables on the Channels and the Main-Channel must comply with the PROFIBUS DP cable specifications for
RS 485 (Fig. 6).
ProfiHub B2FOR+ / B4FOR+ User Manual | August 2019 | © PROCENTEC
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Termination
Isolation
RS 485
Circuit
Circuit
DGND
Isolated Area
Term.
Switch
A
B
I
Indirect grounding
C
C
To direct grounding of
other Channels
), ensuring protection of the
Fig. 5
12/60
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