VEGA VEGAFLEX 55K - Manual (Page 15)

VEGAFLEX 55K 15
Electrical connection
3 Electrical connection
3.1 Connection and connection
cable
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-wire cable
with max. 2.5 mm
2 can be used. Quite often,
the "Electromagnetic pollution" from electronic
actuators, energy lines and transmitting
stations is so considerable that the two-wire
cable should be shielded.
We recommend the use of shielded cable.
Shielding is also a good preventative meas-
ure against future sources of interference.
Ground the shielding only on one 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 Ex applica-
tions, the shielding must be grounded only at
one end. Potential transfer can occur if the
shielding is grounded at both ends.
Ex protection
If an instrument is used in areas endangered
by dust explosion, the necessary regulations
as well as the Ex certificate of VEGAFLEX for
systems in 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 connection cables".
Earth conductor terminal
On VEGAFLEX sensors, the earth conductor
terminal is galvanically connected to the metal
thread.