VEGA VEGAFLEX 83 4 … 20 mA_HART two-wire PFA insulated - Manual (Page 23)

23
5 Connecting to power supply
VEGAFLEX 83 • 4 … 20 mA/HART two-wire
41834-EN-130612
If 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 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 effect against high frequency interfer-
ence signals remains.
Warning:
Significant potential differences exist inside galvanization plants as
well as on vessels with cathodic corrosion protection. Considerable
equalisation currents can flow over the cable screen if the screen is
grounded on both ends.
To avoid this in such applications, the cable screen must be connect-
ed to ground potential only at one end (in the switching cabinet). The
cable screen must not be connected to the internal ground terminal in
the sensor and the outer ground terminal on the housing must not be
connected to the potential equalisation!
Information:
The metallic parts of the instrument (process fitting, transmitter, con-
centric tube, etc.) are conductively connected with the inner and outer
ground terminal on the housing. This connection exists either directly
via connecting metallic parts or, in case of instruments with external
electronics, via the screen of the special connection cable.
You can find specifications on the potential connections inside the
instrument in chapter "Technical data".
5.2 Connecting
The voltage supply and signal output are connected via the spring-
loaded terminals in the housing.
The connection to the display and adjustment module or to the inter-
face adapter is carried out via contact pins in the housing.
Information:
The terminal block is pluggable and can be removed from the
electronics. To do this, lift the terminal block with a small screwdriver
and pull it out. When reinserting the terminal block, you should hear it
snap in.
Proceed as follows:
1. Unscrew the housing cover
2. If a display and adjustment module is installed, remove it by turn-
ing it slightly to the left.
3. Loosen compression nut of the cable entry
4. Remove approx. 10 cm (4 in) of the cable mantle, strip approx.
1 cm (0.4 in) of insulation from the ends of the individual wires
5. Insert the cable into the sensor through the cable entry
Cable screening and
grounding
Connection technology
Connection procedure