VEGA VEGAFLEX 81 Foundation Fieldbus - Manual (Page 69)

69
9 Diagnostics and service
VEGAFLEX 81 • Foundation Fieldbus
44218-EN-130910
Measurement error during filling
Fault description Error pattern Cause Rectification
3. Measured value
jumps towards 0 %
during filling
Level
time 0
– Amplitude of a multiple echo
(vessel top - product surface) is
larger than the level echo
– Check parameter "Application",
especially vessel top, type
of medium, dished end, high
dielectric constant, adapt if
necessary
– The level echo cannot be distin-
guished from the false echo at
a false echo position (jumps to
multiple echo)
– In case of interferences due to
installations in the close range:
Change polarisation direction
– Chose a more suitable installa-
tion position
– Transverse reflection from an
extraction funnel, amplitude of
the transverse reflection larger
than the level echo
– Direct sensor to the opposite
funnel wall, avoid crossing with
the filling stream
4. Measured val-
ue fluctuates around
10 … 20 %
Level
time 0
– Various echoes from an uneven
product surface, e.g. a material
cone
– Check parameter "Type of
medium" and adapt, if neces-
sary
– Optimize installation position
and sensor orientation
– Reflections from the product
surface via the vessel wall
(deflection)
– Select a more suitable installa-
tion position, optimize sensor
orientation, e.g. with a swivel-
ling holder
5. Measured value
jumps sporadically to
100 % during filling
Leve
l
time 0
– Varying condensation or con-
tamination on the antenna
– Carry out a false signal sup-
pression or increase false
signal suppression with con-
densation/contamination in the
close range by editing
– With bulk solids use radar sen-
sor with purging air connection
or flexible antenna cover
Measurement error during emptying
Fault description Error pattern Cause Rectification
6. Measured value re-
mains unchanged in
the close range during
emptying
Level
time 0
– False echo larger than the level
echo
– Level echo too small
– Remove false echoes in the
close range. Check: Antenna
must protrude out of the socket
– Remove contamination on the
antenna
– In case of interferences due to
installations in the close range:
Change polarisation direction
– After removing the false ech-
oes, the false signal suppres-
sion must be deleted. Carry out
a new false signal suppression