VEGA VEGASON 51V…53V - Manual (Page 38)

38 VEGASON 51 V … 53 V
Electrical connection
5 Electrical connection
5.1 Connection and connection
cable
Safety information
Ensure that the instrument is unpressurized
before you start work. Always switch off the
power supply before you carry out clamping
work on the ultrasonic sensors. Protect your-
self and the instruments.
Skilled staff
Instruments which are operated in Ex-areas
must only be connected by skilled staff. The
skilled staff must know the installation condi-
tions and note the attached type approval
and conformity certificates.
Connection
A standard two-wire cable with max. 2,5 mm 2
can be used for connection. Very often the
"electromagnetic pollution" by electronic ac-
tuators, energy lines and transmitting stations
is so considerable that the two-wire line
should be screened.
We recommend to use a screening. This
screening prevents against future interfer-
ences. It is suitable to earth the cable
screens on both ends. However it must be
noted that no earth compensation currents
flow via the screens.
Earth compensation currents can be avoided
with earthing on both ends by connecting the
cable screen on one earth end (e.g. in the
switching cabinet) via a capacitor (e.g. 1
µ
F,
100 V) to the earth potential. Use a very low
impedance earth connection (foundation,
plate or mains earth).
Note:
In Ex-applications the cable screen of the
connection cable must only be earthed at one
end.
Ex-protection
If an instrument is used in hazardous areas
the appropriate regulations, conformity certifi-
cates and type approvals of the sensors and
separators or safety barriers must be noted
(e.g. DIN VDE 0165).
Sensors which are used in Ex-areas must
only be operated on intrinsically safe circuits.
The permissible electrical values are stated in
the conformity certificate or the type approval.
Connection cable
Note that the connection cable must be speci-
fied for the expected operating temperatures
in your systems. The cable must have an outer
diameter of 5 … 9 mm 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.
Earth conductor terminal
On VEGASON 51/52 sensors the earth con-
ductor terminal is galvanically isolated. On
VEGASON 53 sensor the earth conductor
terminal is galvanically connected to the metal
transducer diaphragm.