63
9 Diagnosis, asset management and service
VEGAPULS 64 • 4 … 20 mA/HART - two-wire
51141-EN-160815
1
2
Level
time
0
1 Real level
2 Level displayed by the sensor
Notes:
•
Wherever the sensor displays a constant value, the reason could
also be the fault setting of the current output to "
Hold value
"
•
If the level indication is too low, the reason could be a line resist-
ance that is too high
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
– Incorrect 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, type of
medium, dished bottom, high
dielectric constant, and adapt if
necessary
3. Measured value
jumps towards 100 %
Level
time
0
– Due to the process, the ampli-
tude of the level echo sinks
– A false signal suppression was
not carried out
– Carry out a false signal sup-
pression
– Amplitude or position of a false
signal has changed (e.g. con-
densation, buildup); false signal
suppression no longer matches
actual conditions
– Determine the reason for the
changed false signals, carry out
false signal suppression, e.g.
with condensation
