5 Connecting to power supply
5.1 Preparing the connection
Always keep in mind the following safety instructions:
l Connect only in the complete absence of line voltage
l If overvoltages are expected, install overvoltage arresters
In hazardous areas you should take note of the appropriate
regulations, conformity and type approval certificates of the sensors
and power supply units.
The voltage supply can be 20 … 253 V AC/DC, 50/60 Hz.
The operating voltage of VEGAMET 624 is connected with standard
cable according to the national installation standards.
Standard two-wire cable can be used for connecting the sensors. The
screening is absolutely necessary to ensure interference-free oper-
ation with HART sensors.
Connect the cable screen on both ends to ground potential. In the
sensor, the screen must be connected d irectly to the internal ground
terminal. The ground terminal on the outside of the sensor housing
must be connected to the potential equalisation (low impedance).
If potential equalisation currents are expected, the screen connection
on the side of VEGAMET 624 must be made via a ceramic capacitor
(e. g. 1 nF, 1500 V). The low frequency potential equalisation currents
are thus suppressed, but the protective effect against high frequency
interference signals remains.
Take note of the corresponding installation regulations for Ex
applications. In particular, make sure that no potential equalisation
currents flow over the cable screen. In case of grounding on both sides
this can be achieved by the use of a capacitor or a separate potential
equalisation.
5.2 Connection procedure
Move on to electrical connection and proceed as follows:
1 Snap the socket without VEGAMET 624 onto the carrier rail
2 Connect sensor cable to terminal 1/2 (active input) or 3/4 (passive
input), provide a screening
3 When using several sockets, loop the power supply by means of
bridges
4 Connect power supply (switched off) to terminal 17 and 18
5 If necessary, connect relays or other outputs
Note safety instructions
Take note of sa-
fety instructions
for Ex applica-
tions
Select power supply
Selecting connection
cable
Cable screening and
grounding
Select connec-
tion cable for Ex
applications
12 VEGAMET 624 • 4 … 20 mA/HART signal conditioning instrument
5 Connecting to power su pply
28969-EN-091116
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