Beam angle and false echoes – VEGA VEGASCAN 850 User Manual
Page 37
VEGASCAN 850
37
Beam angle and false echoes
The ultrasonic impulses are focused by the
transducer. The impulses leave the trans-
ducer in conical form similar to the beam
pattern of a spotlight.
Any object inside this emission cone will
cause a false echo. Especially within the first
few meters of the emission cone, pipes,
struts, or other installations can interfere with
the measurement. 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 ultra-
sonic impulses distributes over a large 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.
The illustrations showing the ultrasonic emis-
sion cones are much simplified and repre-
sent only the main beam. However, several
weaker beams also exist. The transducer
must therefore be aligned - especially under
difficult measuring conditions - in such a way
that very low false echo values result. Putting
emphasis only on a strong useful echo is not
sufficient under adverse conditions.
Under difficult measurement conditions, we
recommend looking for a mounting location
with the weakest possible false echoes. The
useful echo will then often appear automati-
cally with sufficient quality. With the adjust-
ment software VVO on the PC you can have
a look at the echo image and optimise the
mounting location (see chapter "6.2 Adjust-
ment with the PC – Sensor optimisation –
Echo curve“).
Mounting and installation
0
0 m
4 m
50 %
0,8
0,8
m
0,4
0,4
100 %
5,5˚
12˚
0
0 m
7 m
50 %
1,2
1,2
m
0,4 0,4
100 %
5,5˚
12˚
0
0 m
15 m
100 %
50 %
1,2
1,2
m
0,4
0,4
3˚
8˚
emitted power
emitted power
VEGASON 51
Meas.
distance
emitted power
emitted power
VEGASON 52
Meas.
distance
emitted power
emitted power
VEGASON 53
Meas.
distance