VEGA VEGAPULS 61 (≥ 2.0.0 - ≤ 3.8) Foundation Fieldbus - Manual (Page 19)

Fig. 14: Agitators
Through the action of filling, stirring and other processes in the vessel,
dense foams which considerably damp the emitted signals may form
on the product surface.
If foams lead to measurement errors, you should use the biggest
possible radar antennas and low frequency radar sensors (C-band).
As an alternative, sensors with guided microwave can be used. These
are unaffected by foam generation and are best suited for such
applications.
By using a standpipe, the influence of vessel installations and
turbulence can be excluded. Under these prerequisites, the meas-
urement of products with low dielectric values (from DK value 1.6) is
possible.
Note:
Measurement in a standpipe is not recommended for very adhesive
products.
Surge or bypass tubes must extend all the way down to the requested
min. level, as measurement is only possible within the tube.
Surge pipe
Make sure you provide the necessary upper vent hole in the surge
pipe. The hole must be aligned so that it and the polarisation marking
on the sensor are in the same plane (see illustration: "Pipe antenna
system in a tank").
Foam generation
Measurement in the
standpipe (surge or by-
pass tube)
VEGAPULS 61 • Foundation Fieldbus 19
4 Mounting
28449
-
EN
-100426