VEGA VEGALOG 571 EA - Manual (Page 12)

5 Connecting to voltage supply
5.1 Preparing the connection
Generally note the following safety instructions:
l
Connect only in the complete absence of line voltage
l
If overvoltage surges are expected, overvoltage arresters
should be installed
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 of the module card is provide via the
common power supply unit of the VEGALOG system.
You can find detailed information on the power supply in
chapter "Technical data" in the "Supplement".
5.2 Connection cable
Power supply is connected with standard cable according to
the national installation standards.
To connect 4 … 20 mA instruments, standard two-wire cable
without screen can be used. If electromagnetic interference is
expected which is above the test values of EN 61326 for
industrial areas, screened cable should be used.
Connect the cable screen on both ends to ground potential.
The screen must be connected (low impedance) on the
4 … 20 mA instrument to the potential equalisation.
If potential equalisation currents are expected, the screen
connection on the side of VEGALOG 571 EA 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 equal-
isation 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.
The total capacitance of the cable and of all capacitors must
not exceed 10 nF in Ex applications.
Note safety instructions
Take note of safety
instructions for Ex
applications
Select power supply
Selecting connection cable
Cable screening and ground-
ing
Select connection
cable for Ex applica-
tions
12 VEGALOG 571 EA - Input card analogue
Connecting to voltage supply
31948
-EN
-070307