Connecting To The Bus System; Preparing The Connection - Vega VEGABAR 86 Operating Instructions Manual

Safety instructions
Voltage supply
Connection cable
Cable screening and
grounding
Cable glands
VEGABAR 86 • Foundation Fieldbus
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 instrument requires a operating voltage of 9 ... 32 V DC. Operat-
ing voltage and the digital bus signal are carried on the same two-wire
connection cable. Power is supplied via the H1 power supply.
Connection is carried out with shielded cable according to Fieldbus
specification.
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
Fieldbus specification. In particular, make sure that the bus is termi-
nated with suitable terminating resistors.
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.
NPT thread
In the case of instrument housings with self-sealing NPT threads, it is
not possible to have the cable entries screwed in at the factory. The
free openings for the cable glands are therefore covered with red dust
protection caps as transport protection.
5 Connecting to the bus system
19