Siemens SITRANS LG240 Operating Instructions Manual page 57

Measurement error with constant level
Fault description
Measured value shows a
too low or too high level
0 time
Measured value jumps to-
wards 100 %
0
time
Measurement error during filling
Fault description
Measured value remains in
the area of the bottom dur-
ing filling
0
time
Measured value remains
momentarily unchanged
during filling and then jumps
to the correct level
0
time
Measured value jumps
sporadically to 100 % dur-
ing filling
0
time
Measured value jumps to
≥ 100 % or 0 m distance
0 time
PBD-51041037
Cause
Min./max. adjustment not correct
Incorrect linearisation curve
Running time error (small measurement
error close to 100 %/serious error close
to 0 %)
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. buildup); false signal
suppression no longer matches
Cause
Echo from the probe end larger than the
product echo, for example, with products
with ε < 2.5 oil-based, solvents, etc.
r
Turbulence on the product surface, quick
filling
Changing condensation or contamina-
tion on the probe
Level echo is no longer detected in the
close range due to false signals in the
close range. The sensor goes into over-
fill protection mode. The max. level (0 m
distance) as well as the status message
"Overfill protection" are output.
SITRANS LG240 - Operating Instructions
Rectification
Adapt min./max. adjustment
Adapt linearisation curve
Repeat setup
Carry out a false signal suppression
Determine the reason for the changed
false signals, carry out false signal sup-
pression, e.g. with buildup
Rectification
Check parameter "Medium" and "Vessel
height", adapt if necessary
Check parameters, change if necessary,
e.g. in dosing vessel, reactor
Carry out a false signal suppression
Eliminate false signals in the close range
Check installation conditions
If possible, switch off the function "Over-
fill protection"
57