VEGA VEGALOG 571 CPU and carrier - Manual (Page 15)

Connect 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 outside on the
sensor housing must be connected to the potential equal-
isation (low impedance).
If potential equalisation currents are expected, the screen
connection on the side of VEGALOG 571 CPU 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.
5.2 Additional instructions for Ex applications
Applications in the area according to the CENELEC Ex
protective reguations and ElexV (Germany) zone 0 require the
use of approved sensors.
For these applications, not the respective legal documents
(test certificates, test notes and conformity certificates). These
belong to the scope of delivery of the respecitive instrument.
These sensors must only be powered via an intrinsically safe
circuit. With the EA card, the sensors must be connected via a
safety barrier. The EP card is available in Ex version, no
separate separating facility necessary.
Also note the legal documents of these instruments.
To mount, note the following:
l
VEGALOG 571 as well as the used separting facilities
must be only used outside the Ex area.
l
A separating wall must be provided between the con-
nection parts of intrinsically safe and non-intrinsically safe
circuits so that there is a min. distance of 50 mm
l
Only one sensor must be connected to each safety barrier
Cable screening and ground-
ing
Select connection
cable for Ex applica-
tions
Mounting instructions
VEGALOG 571 - CPU and carrier 15
Connecting to power supply
31947
-EN
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