Siemens SITRANS LG250 Operating Instructions Manual page 63

Measurement error with constant level
Fault description
1. Measured value
shows a too low or too
high level
2. Measured value
jumps towards 100 %
Measurement error during filling
Fault description
3. Measured value re-
mains in the area of the
bottom during filling
4. Measured value re-
mains momentarily
unchanged during fill-
ing and then jumps to
the correct level
5. Measured value
jumps sporadically to
100 % during filling
6. Measured value
jumps to ≥ 100 % or
0 m distance
PBD-51041387
Error pattern Cause
– Min./max. adjustment not
correct
– Incorrect linearization curve
0
time
– 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
0 time
not carried out
– Amplitude or position of a
false signal has changed (e.g.
buildup); false signal suppres-
sion no longer matches
Error pattern Cause
– Echo from the probe end larger
than the product echo, for
example, with products with
ε < 2.5 oil-based, solvents, etc.
r
0 time
– Turbulence on the product
surface, quick filling
0 time
– Changing condensation or
contamination on the probe
0
time
– Level echo is no longer
detected in the close range
due to false signals in the close
range. The sensor goes into
overfill protection mode. The
0
time
max. level (0 m distance) as
well as the status message
"Overfill protection" are output-
ted.
SITRANS LG250 - Operating Instructions
Rectification
– Adapt min./max. adjustment
– Adapt linearization curve
– Repeat setup
– Carry out a false signal sup-
pression
– Determine the reason for the
changed false signals, carry out
false signal suppression, e.g.
with buildup
Rectification
– Check parameter "Medium"
and "Vessel height", adapt if
necessary
– Check parameters, change if
necessary, e.g. in dosing ves-
sel, reactor
– Carry out a false signal sup-
pression
– Eliminate false signals in the
close range
– Check installation conditions
– If possible, switch off the func-
tion "Overfill protection"
63