VEGA VEGASON 65 Foundation Fieldbus - Manual (Page 24)

5 Connecting to power supply
5.1 Preparing the connection
A
lways keep in mind the following safety instructions:
l C onnect only in the complete absence of line voltage
l I f overvoltages are expected, install overvoltage arresters
Tip:
W
e recommend using VEGA overvoltage arresters FS-LB-I and
ÜSB 62-36G.X.
I n hazardous areas you should take note of the appropriate
regulations, conformity and type approval certificates of the sensors
and power supply units.
P ower supply and current output are transmitted via separate two-wire
connection cables. The supply voltage range can differ depending on
the instrument version. The exact range is stated in the "Technischen
Daten".
T
he standard version can be operated with an earth-connected current
output, the Exd version must be operated with a floating output.
T his instrument is designed in protection class I. To maintain this
protection class, it is absolutely necessary that the ground conductor
be connected to the internal ground terminal. Take note of the general
installation regulations.
A s a rule, connect VEGASON 65 to vessel ground (potential
euqalisation) or in case of plastic vessels to the next ground potential.
F
or this purpose, there is a ground terminal on the side of the
instrument housing.
F
or power supply, an approved installation cable with PE conductor is
necessary.
T he 4 … 20 mA current output is connected with standard two-wire
cable without screen. The outer cable diameter of 5 … 9 mm ensures
the seal effect of the cable gland. If strong electromagnetic
interference is expected, screened cable should be used.
C onnect the cable screen on both ends to ground potential. In the
sensor, the screen must be connected directly to the internal ground
terminal. The ground terminal on the outside of the housing must be
connected to the potential equalisation (low impedance).
I f potential equalisation currents are expected, the connection on the
processing side must be made via a ceramic capacitor (e. g. 1 nF,
1500 V). T
he low frequency potential equalisation currents are thus
suppressed, but the protective effect against high frequency interfer-
ence signals remains.
Note safety instructions
Take note of
safety instruc-
tions for Ex ap-
plications
Select power supply
Selecting connection
cable
Cable screening and
grounding
24 VEGASON 65 • F oundation Fieldbus
5 C onnecting to power supply
28794
-EN
-081127