VEGA VEGAPULS 56 Profibus PA - Manual (Page 23)

VEGAPULS 56 Profibus PA 23
0
10 m
0 m
20 m
20˚
30˚
50 %
3,5 m
5,0 m
3,5 m
5,0 m
100 %
0
10 m
0 m
20 m
30˚
40˚
100 %
50 %
5,3 m 5,3 m
6,8 m 6,8 m
Emission cone of a DN 100 horn antenna
Meas. distance
Emission cone and false reflections
The radar signals are focused by the an-
tenna system. The signals leave the antenna
in a conical path similar to the beam pattern
of a spotlight. This emission cone depends
on the antenna used.
Any object in this beam cone causes a reflec-
tion of the radar signals. Within the first few
meters of the beam cone, tubes, struts or
other installations can interfere with the meas-
urement. At a distance of 6 m, the false echo
of a strut has an amplitude nine times greater
than at a distance of 18 m.
At greater distances, the energy of the radar
signal distributes itself over a larger area,
thus causing weaker echoes from obstruct-
ing surfaces. The interfering signals are
therefore less critical than those at close
range.
If possible, orient the sensor axis perpen-
dicularly to the product surface and avoid
vessel installations (e.g. pipes and struts)
within the 100 % area of the emission cone.
If possible, provide a "clear view“ of the
product inside the emission cone and avoid
vessel installations in the first third of the
emission cone.
Optimum measuring conditions exist when
the emission cone reaches the measured
product perpendicularly and when the emis-
sion cone is free from obstructions.
Mounting and installation
Emission cone of a DN 150 horn antenna
Meas. distance
emitted power
emitted power
emitted power