VEGA VEGAPULS 45 4 … 20 mA; HART compact sensor - Manual (Page 10)

10 VEGAPULS 42, 44 and 45 – 4 … 20 mA
2.2 Antennas
The antenna is the eye of the radar sensor.
The shape of the antenna, however, doesn’t
give a casual observer the slightest clue on
how carefully the antenna geometry must be
adapted to the physical properties of electro-
magnetic waves. The geometrical form deter-
mines focal properties and sensitivity - the
same way it determines the sensitivity of a
unidirectional microphone.
For different applications and process re-
quirements, series 40 sensors are manufac-
tured in three basic versions: as VEGAPULS
42, VEGAPULS 44 and VEGAPULS 45.
VEGAPULS 42 sensors are distinguished by
a G 1½
A or 1½“ NPT threaded mounting
boss as process connection. These sensors
are equipped in standard versions with a
ø 40 mm horn antenna.
VEGAPULS 44 sensors typically have DIN or
ANSI flanges as process connection. In
standard versions, they are manufactured
with DN 50, 80, 100 and 150, as well as with
ANSI 2“, 3“, 4“ and 6“. The bigger flanges are
equipped with respectively bigger antenna
horns (ø 48, 75 and 95 mm).
Generally speaking: The bigger the antenna
horn, the better the focussing characteristics
and the better the antenna gain. This ensures
that even a weak level echo will be reliably
detected as a level echo.
VEGAPULS 45 sensors are distinguished by
an integrated measuring tube. The measur-
ing tube serves as a waveguide for the radar
signals and allows no transmitting energy to
be lost. The entire transmission energy re-
turns as reflection energy, enabling reliable
detection also of products with very weak
reflection characteristics such as e.g. light
petrol, liquid gas etc. with
ε
r
-values of
1.4 … 2.0. Viscous or adhesive products
cannot be measured with VEGAPULS 45.
Horn antennas
Horn antennas focus the
radar signals very well.
Made of 1.4435 (stainless
steel) or Hastelloy C22, they
are very rugged, and physi-
cally as well as chemically
resistant. They are suitable
for pressures up to 40 bar
and for product tempera-
tures up to 150 °C. The horn
diameters determine the
focussing of the radar sig-
nals. The bigger the horn
diameter (40, 48, 75,
95 mm), the bigger the
antenna gain. The antenna
gain represents the ratio of
transmitted energy to re-
ceived echo energy.
VEGAPULS 42
VEGAPULS 44
Types and versions