Vega VEGAPULS 67 Operating Instructions Manual page 64

9 Diagnosis, asset management and service
Measurement error with constant level
Fault description
1. Measured value
shows a too low or too
high level
2. Measured value
jumps towards 100 %
Measurement error during filling
Fault description
3. Measured value
jumps towards 0 %
during filling
4. Measured val-
ue fluctuates around
10 ... 20 %
5. Measured value
jumps sporadically to
100 % during filling
64
Error pattern Cause
– Min./max. adjustment not
correct
– Incorrect linearization curve
0
time
– Due to the process, the
amplitude of the product echo
decreases
– A false signal suppression was
0 time
not carried out
– Amplitude or position of a false
signal has changed (e.g. con-
densation, buildup); false signal
suppression no longer matches
actual conditions
Error pattern Cause
– Amplitude of a multiple echo
(vessel top - product surface) is
larger than the level echo
0
time
– The level echo cannot be distin-
guished from the false signal at
a false signal position (jumps to
multiple echo)
– Transverse reflection from an
extraction funnel, amplitude of
the transverse reflection larger
than the level echo
– Various echoes from an uneven
product surface, e.g. a material
cone
0 time
– Reflections from the product
surface via the vessel wall
(deflection)
– Changing condensation or con-
tamination on the antenna
0 time
Rectification
– Adapt min./max. adjustment
– Adapt linearization curve
– Carry out a false signal sup-
pression
– Determine the reason for the
changed false signals, carry out
false signal suppression, e.g.
with condensation
Rectification
– Check parameter "Application",
especially vessel top, type of
medium, dished bottom, high
dielectric constant, and adapt if
necessary
– Remove/reduce false signal:
minimize interfering installa-
tions by changing the polariza-
tion direction
– Chose a more suitable installa-
tion position
– Direct sensor to the opposite
funnel wall, avoid crossing with
the filling stream
– Check parameter "Type of
medium" and adapt, if neces-
sary
– Optimize installation position
and sensor orientation
– Select a more suitable installa-
tion position, optimize sensor
orientation, e.g. with a swivel-
ling holder
– 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
VEGAPULS 67 • 4 ... 20 mA/HART - four-wire