Siemens SITRANS LG270 Operating Instructions Manual page 53

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
PBD-51041071
•
Constant level
•
Filling
•
Emptying
The images in column "Error pattern" show the real level as a broken
line and the level displayed by the sensor as a continuous line.
Fig. 21: 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"
•
If the level indication is too low, the reason could be a line resist-
ance that is too high
Error pattern Cause
•
Min./max. adjustment not
correct
•
Incorrect linearisation curve
•
0
time
Running time error (small meas-
urement 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 not carried out
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 exam-
ple, with products with ε
oil-based, solvents, etc.
0
time
SITRANS LG270 - Operating Instructions
0
Rectification
•
Adapt min./max. adjustment
•
Adapt linearisation curve
•
Repeat setup
•
Carry out a false signal suppres-
sion
•
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
< 2.5 necessary
r
1
2
time
53