Vega VEGAPULS 63 - 9 Measurement Errors: Constant Level; Errors During Constant Level Measurement

67
9 Diagnosis, asset management and service
VEGAPULS 63 • Modbus and Levelmaster protocol
41364-EN-170711
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 Reason Rectication
1. Measured value
shows a too low or too
high level
Level
time
0
•
Min./max. adjustment not
correct
•
Adapt min./max. adjustment
•
Incorrect linearisation curve
•
Adapt linearisation 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 suppres-
sion
•
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
Measurementerrorduringlling
Fault description Error pattern Reason Rectication
4. Measured value re-
mains unchanged
duringlling
Level
time
0
•
False signals in the close range
too big or level echo too small
•
Strong foam or spout generation
•
Max. adjustment not correct
•
Eliminate false signals in the
close range
•
Check measurement situation:
Antenna must protrude out of
the socket, installations
•
Remove contamination on the
antenna
•
In case of interferences due to
installations in the close range:
Change polarisation direction
•
Create a new false signal sup-
pression
•
Adapt max. adjustment
5. Measured value re-
mains in the bottom
sectionduringlling
Level
time
0
•
Echo from the tank bottom
larger than the level echo, for
example, with products with
ε
r
< 2.5 oil-based, solvents
•
Check parameters Medium,
Vessel height and Floor form,
adapt if necessary