VEGA VEGAPULS 56 Profibus PA - Manual (Page 13)

VEGAPULS 56 Profibus PA 13
Product description
DN 150
DN 250
DN 50
DN 80
Pipe antenna
Only in conjunction with a meas-
uring tube, i.e. with a surge or
bypass tube (which can also be
angled), do horn antennas form
a complete antenna system.
Pipe antennas are mainly suit-
able for very agitated products
or for products with very small
dielectric constant.
The antenna can be with or with-
out horn. The antennas are char-
acterised by a very high antenna
gain. High reliability can be
achieved even with products
having poor reflective proper-
ties.
For the radar signals, the meas-
uring tube acts as a conductor.
The running time of the radar
signal changes in the tube and
depends on the tube diameter.
Therefore, the sensor must be
informed about the tube inner
diameter so that the change in
the running time can be taken
into account and precise level
signals ensured.
1.5 Antennas
The antenna is the eye of the radar sensor.
An uninitiated observer would probably not
realise how carefully the antenna geometry
must be adapted to the physical properties
of electromagnetic fields.
The geometrical form determines focal prop-
erties and sensitivity - the same way it deter-
mines the sensitivity of a unidirectional
microphone.
For different applications and process re-
quirements various antenna systems are
available.
Horn antenna
Horn antennas focus the
radar signals very well.
Made of 1.4571 (stainless
steel) or Hastelloy C22 they
are very rugged, and
physically as well as
chemically resistant.
Horn antennas are used for
measurement in closed or
open vessels.