VEGA VEGAPULS 45 VBUS - Manual (Page 12)

12 VEGAPULS 42, 44 and 45 – VBUS
2.3 Antennas
The antenna is the eye of the radar sensor. A
casual observer would never guess how
carefully the antenna geometry must be
adapted to the physical properties of electro-
magnetic fields. The geometrical form deter-
mines focal properties and sensitivity - the
same way it determines the sensitivity of a
unidirectional microphone.
For various application purposes, measure-
ment conditions and process requirements,
series 40 sensors are available with three
antenna forms as VEGAPULS 42,
VEGAPULS 44 and VEGAPULS 45.
VEGAPULS 42 sensors are characterised by
G 1
1 /
2
A or 1 1 /
2
" NPT thread as process fitting.
These sensors are equipped as standard
versions with a ø 40 mm horn as antenna.
VEGAPULS 44 sensors are characterised by
a DIN or ANSI flanges as process fitting. In
standard version they are manufactured with
DN 50, 80, 100 and 150 as well as with ANSI
2", 3", 4" and 6". The bigger flanges come
equipped with respectively larger antenna
horns (ø 48, 75 and 95 mm).
Generally: The bigger the antenna horn, the
better the focusing characteristics, and the
better the antenna gain. This ensures that
even a weak product echo can be detected
reliably as level echo.
VEGAPULS 45 sensors are characterised by
integrated measuring tube. The measuring
tube serves the radar signals as a
waveguide in which no emitted energy is lost.
The complete emitted energy is returned as
reflection energy. Due to this, also products
with very weak reflection characteristics,
such as light petrol, liquid gas with
ε
r
values
of 1.4 … 2.0 can be reliably detected.
Viscous or adhesive products cannot be
measured with VEGAPULS 45.
Horn antennas
Horn antennas focus the
radar signals very well.
Manufactured from 1.4435
(StSt) or Hastelloy C22, they
are very rugged, and both
physically and chemically
resistant. They are suitable
for pressures up to 40 bar
and for medium tempera-
tures up to 150°C. The horn
diameters determine the
focusing of the radar sig-
nals. The antenna gain in-
creases with increasing horn
diameter (40, 48, 75,
95 mm).
The antenna gain represents
the relation between
transmitted energy and
received echo energy.
VEGAPULS 42
VEGAPULS 44
Types and versions