VEGA VEGAPULS 41 Profibus PA - Manual (Page 25)

VEGAPULS 41 – Profibus PA 25
27292-EN-041227
Pipe antenna: The surge pipe open to the bottom
must have a ventilation or equalisation hole on top
Correct Incorrect
Standpipe installation mistakes
Pipe antenna without ventilation hole
Pipe antenna systems must be provided with
a ventilation hole on the upper end of the
surge pipe. If this hole is absent, incorrect
measurements will result.
Foam generation
Conductive
foam
Liquid
Mounting and installation
If there are good reflection conditions (liquid
medium, no installations), we recommend
locating the sensor where there is no vessel
wall within the inner emission cone. For prod-
ucts in less favourable reflection environ-
ments, it is a good idea to also keep the outer
emission cone free of interfering installations.
Note chapter "3.1 General installation instruc-
tions“.
Foam generation
Conductive foam is penetrated by radar
signals to different depths and generates a
number of individual (bubble) echoes. In
addition, the signals are damped in foam,
which is comparable to the damping of heat
radiation by Styrofoam. Thick, dense, creamy
and conductive foam can cause incorrect
measurements.
Provide preventative measures against foam
or measure in a bypass tube. Check, if nec-
essary, the possibility of using a different
measurement technology, e.g. capacitive
electrodes or hydrostatic pressure transmit-
ters. In many cases, VEGAPULS 54 radar
sensors with 5.8 GHz operating frequency
achieve considerably better and more reli-
able measuring results in foam applications
than series 40 sensors with 26 GHz technol-
ogy.
VEGAPULS on the surge pipe: The sensor type plate
must be aligned with the rows of holes
Type label
Correct Incorrect
Wrong polarisation direction
When measuring in a surge pipe, especially if
there are holes or slots for mixing in the tube,
it is important that the radar sensor is aligned
with the rows of holes.
The two rows of holes (displaced by 180°) of
the measuring tube must be in the same
plane as the polarisation direction of the
radar signals. The polarisation direction is
always in the same plane as the type label.