VEGA VEGAFLEX 51K - Manual (Page 15)

VEGAFLEX 51K 15
Electrical connection
3 Electrical connection
3.1 Connection and connection ca-
ble
Safety information
As a rule, do all work in the complete ab-
sence of line voltage. Always switch off the
power supply before you carry out connect-
ing work on the sensors. Protect yourself
and the instrument, especially when you use
sensors which do not work with low voltage.
Qualified personnel
Instruments which are not operated with a
protective low voltage must only be con-
nected by qualified personnel.
Connection
For connection, a standard two or four-wire
cable (sensors with separate supply) with
max. 2.5 mm
2 can be used. Very often the
"Electromagnetic pollution“ from electronic
actuators, energy lines and transmitting
stations is so considerable that the two or
four-wire cable should be shielded.
We recommend the use of screened cable.
Shielding is also a good preventative meas-
ure against future soures of interference.
Ground the shielding only on the sensor end
(fig. 3.1 a). It is advantageous to ground the
shielding on both ends. However, you must
make sure that no earth equalisation currents
flow through the cable shielding (fig. 3.1 b).
Earth equalisation currents (when grounding
at both ends) can be prevented by connect-
ing the cable shielding on one end (e.g. in
the switching cabinet) via a capacitor (e.g.
0.1 µF; 250 V AC) to the earth potential. Use
a very low-resistance earth connection (foun-
dation, plate or mains earth). In StEx applica-
tions, the shielding should be grounded only
at the one end. Potential transfer can be
caused when grounding at both ends.
Ex protection
If an instrument is used in dust-Ex areas,
respective regulations as well as the dust-Ex
certificate of VEGAFLEX for systems in dust-
Ex areas should be noted.
Connection cable
Make sure that the connection cables are
specified for the expected operating tempera-
tures in your systems.
The cable must have an outer diameter of
5 … 9 mm (1/5 ... 1/3 inch). Otherwise the seal
effect of the cable entry will not be ensured.
Cables for intrinsically safe circuits must be
marked blue and must not be used for other
circuits. Note the special wiring regulations
for Profibus PA sensors (P), see "1.5 Techni-
cal data“.
Earth conductor terminal
On VEGAFLEX sensors, the earth conductor
terminal is galvanically connected with the
metal thread.