VEGA VEGABAR 74 4 … 20 mA_HART User Manual
Page 14
industrial areas, screened cable should be used. For HART
multidrop operation we recommend as standard practice the
use of screened cable.
1
2
Fig. 3: Connection of VEGABAR 74
1
Direct connection
2
Connection via VEGABOX 02 or VEGADIS 12
I
f screened cable is necessary, connect the cable screen on
both ends to ground potential. In the VEGABOX 02 or
VEGADIS
12,
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). The low frequency potential equalisation
currents are thus suppressed, but the protective effect against
high frequency interference signals remains.
T
ake 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.
Cable screening and ground-
ing
Select connection
cable for Ex applica-
tions
14
VEGABAR
74 - 4 … 20
mA/HART
C
onnecting to power supply
28432
-EN
-070718