Vega VEGAPULS 63 Operating Instructions Manual page 55

Measurement error with constant level
Fault description
1. Measured value
shows a too low or too
high level
2. Measured value
jumps towards 0 %
3. Measured value
jumps towards 100 %
Measurement error during filling
Fault description
4. Measured value re-
mains unchanged
during filling
5. Measured value re-
mains in the bottom
section during filling
6. Measured value re-
mains momentarily
unchanged during fill-
ing and then jumps to
the correct level
VEGAPULS 63 • 4 ... 20 mA/HART two-wire
Error pattern Cause
– Min./max. adjustment not
correct
– Wrong linearization curve
0 – Installation in a bypass tube or
time
standpipe, hence running time
error (small measurement error
close to 100 %/large error close
to 0 %)
– Multiple echo (vessel top,
product surface) with amplitude
higher than the level echo
0
time
– Due to the process, the ampli-
tude of the product echo sinks
– A false signal suppression was
not carried out
0 time
– Amplitude or position of a
false echo has changed (e.g.
condensation, buildup); false
signal suppression no longer
matches
Error pattern Cause
– False echoes in the close range
too big or product echo too
small
– Strong foam or spout genera-
tion
0
time
– Max. adjustment not correct
– Echo from the tank bottom
larger than the product echo,
for example, with products with
ε < 2.5 oil-based, solvents
r
0 time
– Turbulence on the product
surface, quick filling
0
time
9 Diagnosis, Asset Management and service
Rectification
– Adapt min./max. adjustment
– Adapt linearization curve
– Check parameter "Application"
with respect to vessel form,
adapt if necessary (bypass,
standpipe, diameter)
– Check parameter "Application",
especially vessel top, product
type, dished end, high dielectric
figure, adapt if necessary
– Carry out false signal suppres-
sion
– Determine the reason for the
changed false signals, carry out
false signal suppression, e.g.
with condensation
Rectification
– Eliminate false echoes in the
close range
– Check measurement situation:
Antenna must protrude out of
the socket, installations
– Remove contamination on the
antenna
– Minimize interfering instal-
lations in the close range by
changing the polarization
direction
– Create a new false signal sup-
pression
– Adapt max. adjustment
– Check application parameters
Medium, Vessel height and
Floor form, adapt if necessary
– Check application parameters,
change if necessary, e.g. in
dosing vessel, reactor
55