Vega POINTRAC 31 - Page 22

22
5 Connecting to power supply
POINTRAC 31 • 8/16 mA/HART - four-wire
43388-EN-180322
You have to remove these plugs before electrical connection.
NPT thread
In the case of instrument housings with self-sealing NPT threads, it is
not possible to have the cable entries screwed in at the factory. The
free openings for the cable glands are therefore covered with red dust
protection caps as transport protection.
Before setup you have to replace these protective caps with approved
cable glands or close the openings with suitable blind plugs. Unused
cableglandsdonotprovidesucientprotectionagainstmoistureand
must be replaced with blind plugs.
The suitable cable glands and blind plugs come with the instrument.
If screened cable is required, 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 equalisa-
tion (low impedance).
If 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eectagainsthighfrequencyinterfer-
ence signals remains.
Warning:
Signicantpotentialdierencesexistinsidegalvanizationplantsas
well as on vessels with cathodic corrosion protection. Considerable
equalisationcurrentscanowoverthecablescreenifthescreenis
grounded on both ends.
To avoid this, the cable screen in such applications must be con-
nected only on one end to ground potential in the switching cabinet.
The cable screen must not be connected to the inner ground terminal
in the sensor and the outer ground terminal on the housing must not
be connected to potential equalization!
Information:
The metal parts of the instrument are conductively connected with
the inner and outer ground terminal on the housing. This connection
is either a direct metallic connection or, in case of instruments with
external electronics, a connection via the screen of the special con-
nection cable.
Youcanndspecicationsonthepotentialconnectionsinsidethe
instrument in chapter "Technical data".
The voltage supply and signal output are connected via the spring-
loaded terminals in the housing.
Connection to the display and adjustment module or to the interface
adapter is carried out via contact pins in the housing.
Proceed as follows:
The procedure applies to instruments without explosion protection.
Cable screening and
gr
ounding
Connection technology
Connection procedure