Vega VEGAPULS 21 Operating Instructions Manual page 40

11 Diagnostics and servicing
Liquids: Measurement error during emptying
Fault description
Measured value remains un-
changed in the close range
during emptying
0
time
Measured value jumps spo-
radically towards 100 %
during emptying
0
time
Bulk solids: Measurement error at constant level
Fault description
Measured value shows a too
low or too high level
0
time
Measured value jumps to-
wards 100 %
0 time
Bulk solids: Measurement error during filling
Fault description
Measured value jumps to-
wards 0 % during filling
0 time
40
Cause
False signal larger than the level echo
Level echo too small
Varying condensation or contamination
on the antenna
Cause
Min./max. adjustment not correct
Incorrect linearisation curve
Due to the process, the amplitude of the
product echo decreases
A false signal suppression was not car-
ried out
Amplitude or position of a false signal
has changed (e.g. condensation, build-
up); false signal suppression no longer
matches actual conditions
Cause
The level echo cannot be distinguished
from the false signal at a false signal po-
sition (jumps to multiple echo)
Transverse reflection from an extraction
funnel, amplitude of the transverse re-
flection larger than the level echo
Rectification
Check measuring point: Antenna should
protrude out of the threaded mounting
socket, possible false echoes through
flange socket?
Remove contamination on the antenna
In case of interferences due to instal-
lations in the close range: Change
polarisation direction
After eliminating the false signals, the
false signal suppression must be de-
leted. Carry out a new false signal
suppression
Carry out false signal suppression or in-
crease false signal suppression in the
close range by editing
With bulk solids, use radar sensor with
purging air connection
Rectification
Adapt min./max. adjustment
Adapt linearisation curve
Carry out a false signal suppression
Determine the reason for the changed
false signals, carry out false signal sup-
pression, e.g. with condensation.
Rectification
Remove/reduce false signal: minimize
interfering installations by changing the
polarization direction
Chose a more suitable installation po-
sition
Direct sensor to the opposite fun-
nel wall, avoid crossing with the filling
stream
VEGAPULS 21 • Two-wire 4 ... 20 mA/HART