VEGA VEGAFLEX 66 (-110…+400°C) 4 … 20 mA_HART - four-wire - Manual (Page 19)

U
se cable with round cross-section. A cable outer diameter of
5 … 9 mm (0.2 … 0.35 in) ensures the seal effect of the cable
gland. If you are using cable with other diameter or cross-
section, you have to exchange the seal or use a suitable cable
gland.
I
f screened cable is necessary, 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 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.
W ith the Exd version, the minus side of the signal output is
galvanically connected to ground via protective diodes. When
connecting the instrument to a grounded PLC, equalising
currents can flow in case of potential differences which can
cause malfunctions. Make sure that there is sufficient potential
equalisation from the system side or realise the connection via
switching amplifier.
5.2 Connection procedure
P roceed as follows:
1 U nscrew the housing cover
2 L oosen compression nut of the cable entry
3 R emove approx. 10 cm (4 in) of the cable mantle (current
output), strip approx. 1 cm (0.4 in) insulation from the ends
of the individual wires
4 I nsert the cable through the cable gland into the sensor
5 L ift the opening levers of the terminals with a screwdriver
6 I nsert the wire ends into the open terminals according to
the wiring plan
Cable screening and
grounding
Installation with
Ex applications
VEGAFLEX 66 • 4 … 20 mA/HART - four-wire 19
5 C onnecting to power supply
32763
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EN
-080826