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5 Connecting to the bus system
VEGABAR 82 • Profibus PA
45031-EN-220624
5 Connecting to the bus system
5.1 Preparing the connection
Always keep in mind the following safety instructions:
•
Carry out electrical connection by trained, qualified personnel
authorised by the plant operator
•
If overvoltage surges are expected, overvoltage arresters should
be installed
Warning:
Only connect or disconnect in de-energized state.
The voltage supply is provided by a Profibus DP /PA segment coupler.
The voltage supply range can differ depending on the instrument
version. You can find the data for voltage supply in chapter "
Technical
data
".
Connection is made with shielded cable according to the Profibus
specification. Power supply and digital bus signal are carried over the
same two-wire connection cable.
Use cable with round cross section for instruments with housing and
cable gland. To ensure the seal effect of the cable gland (IP protection
rating), find out which cable outer diameter the cable gland is suitable
for.
Use a cable gland fitting the cable diameter.
Make sure that the entire installation is carried out according to the
Profibus specification. In particular, make sure that the bus is termi-
nated with suitable terminating resistors.
You can find detailed information of the cable specification, installa-
tion and topology in the "
Profibus PA - User and Installation Guide
-
line
" on www.profibus.com.
Make sure that the cable screen and grounding are carried out ac-
cording to Fieldbus specification. We recommend to connect the
cable screening to ground potential on both ends.
In systems with potential equalisation, connect the cable screening
directly to ground potential at the power supply unit, in the connection
box and at the sensor. The screen in the sensor must be connected
directly to the internal ground terminal. The ground terminal outside
on the housing must be connected to the potential equalisation (low
impedance).
Metric threads:
In the case of instrument housings with metric thread, the cable
glands are screwed in at the factory. They are sealed with plastic
plugs as transport protection.
Note:
You have to remove these plugs before electrical connection.
Safety instructions
Voltage supply
Connection cable
Cable screening and
grounding
Cable glands
