Siemens SITRANS LG270 Operating Instructions Manual page 68

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
68
•
Constant level
•
Filling
•
Emptying
The images in column "Error pattern" show the real level with a bro-
ken line and the level displayed by the sensor as a continuous line.
Fig. 31: The broken line 1 shows the real level, the continuous line 2 shows the
level displayed by the sensor
Note:
•
Wherever the sensor displays a constant value, the reason could
also be the fault setting of the current output to "Hold value"
•
In case of a too low level indication, the reason could be a line
resistance that is too high
Error pattern Cause
– Min./max. adjustment not
correct
– Wrong linearization curve
0 – Running time error (small
time
measurement error close to
100 %/serious error close to
0 %)
– Due to the process, the ampli-
tude of the product echo sinks
– A false signal suppression was
not carried out
0
time
– 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
SITRANS LG270 - Operating Instructions
0
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
1
2
time
PBD-51041066