Siemens SITRANS LR120 Modbus Operating Instructions Manual page 43

Diagnostics and troubleshooting
9.4 Treatment of measurement errors
Fault description
Measured value shows a
too low or too high level
Measured value jumps
towards 100 %
Fault description
Measured value remains
unchanged during filling
Measured value jumps
towards 0 % during filling
Measured value jumps
towards 100 % during
filling
36
Cause
Min./max. adjustment not correct
Incorrect linearization curve
Due to the process, the amplitude
of the level echo sinks
A auto false echo suppression was
not carried out
Amplitude or position of a
false signal has changed (e.g.
condensation, buildup); auto
false echo suppression no longer
matches actual conditions
Cause
False signals in the close range too
big or level echo too small
Strong foam or vortex generation
Max. adjustment not correct
The level echo cannot be
distinguished from the false signal
at a false signal position (jumps to
multiple echo)
Due to strong turbulence and
foam generation during filling, the
amplitude of the level echo sinks.
Measured value jumps to false
signal
Rectification
Adapt min./max. adjustment
Adapt linearization curve
Carry out a auto false echo
suppression
Determine the reason for the
changed false signals, carry out
auto false echo suppression, e.g.
with condensation.
Rectification
Eliminate false signals in the close
range
Check measuring point: Antenna
should protrude out of the threaded
mounting nozzle, possible false
echoes through flange nozzle?
Remove contamination on the
antenna
In case of interferences due to
installations in the close range,
change polarisation direction
Create a new auto false echo
suppression
Adapt max. adjustment
In case of interferences due to
installations in the close range:
Change polarisation direction
Chose a more suitable installation
position
Carry out a auto false echo
suppression
Operating Instructions, 10/2022, 62709-76-01, A5E49829030
SITRANS LR120 Modbus