68
9 Diagnosis, asset management and service
VEGAPULS 67 • Profibus PA
36533-EN-170405
Measurement error during filling
Fault description
Error pattern
Reason
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 bottom, high
dielectric constant, and adapt if
necessary
•
The level echo cannot be distin-
guished from the false signal at
a false signal position (jumps to
multiple echo)
•
Remove/reduce false signal:
minimize interfering installations
by changing the polarization
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 swivelling
holder
5. Measured value
jumps sporadically to
100 % during filling
Level
time
0
•
Changing condensation or con-
tamination on the antenna
•
Carry out a false signal suppres-
sion or increase false signal
suppression with condensation/
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
Reason
Rectification
6. Measured value re-
mains unchanged in
the close range during
emptying
Level
time
0
•
False signal larger than the level
echo
•
Level echo too small
•
Eliminate false signals in the
close range. Check: Antenna
must protrude out of the socket
•
Remove contamination on the
antenna
•
Minimize interfering installations
in the close range by changing
the polarization direction
•
After eliminating the false sig-
nals, the false signal suppres-
sion must be deleted. Carry out
a new false signal suppression