VEGA VEGAPULS 66 (≥ 2.0.0 - ≥ 4.0.0) enamel 4 … 20 mA_HART - four-wire - Manual (Page 53)

53
9 Diagnosis, Asset Management and service
VEGAPULS 66 enamel • 4 … 20 mA/HART - four-wire
36528-EN-121011
9.4 Measurement error with constant level
Fault description Error pattern Cause Rectification
1. Measured value
shows a too low or too
high level
Level
time 0
– Min./max. adjustment not
correct
– Adapt min./max. adjustment
– Wrong linearization curve – Adapt linearization curve
– Installation in a bypass tube or
standpipe, hence running time
error (small measurement error
close to 100 %/large error close
to 0 %)
– Check parameter "Application"
with respect to vessel form,
adapt if necessary (bypass,
standpipe, diameter)
2. Measured value
jumps towards 0 % Level
time 0
– Multiple echo (vessel top,
product surface) with amplitude
higher than the level echo
– Check parameter "Application",
especially vessel top, product
type, dished end, high dielectric
figure, adapt if necessary
3. Measured value
jumps towards 100 % Level
time 0
– Due to the process, the ampli-
tude of the product echo sinks
– A false signal suppression was
not carried out
– Carry out false signal suppres-
sion
– Amplitude or position of a
false echo has changed (e.g.
condensation, buildup); false
signal suppression no longer
matches
– Determine the reason for the
changed false echo, carry out
false signal suppression, e.g.
with condensation
9.4 Measurement error during filling
Fault description Error pattern Cause Rectification
4. Measured value re-
mains unchanged
during filling
Level
time 0
– False echoes in the close range
too big or product echo too
small
– Strong foam or spout genera-
tion
– Max. adjustment not correct
– 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
5. Measured value re-
mains in the bottom
section during filling
Level
time 0
– Echo from the tank bottom
larger than the product echo,
for example, with products with
ε
r
< 2.5 oil-based, solvents
– Check application parameters
Medium, Vessel height and
Floor form, adapt if necessary
6. Measured value re-
mains momentarily
unchanged during fill-
ing and then jumps to
the correct level
Level
time 0
– Turbulence on the product
surface, quick filling
– Check application parameters,
change if necessary, e.g. in
dosing vessel, reactor