Siemens SITRANS LG260 Operating Instructions Manual page 48

Treatment of measure-
ment errors with bulk
solids
Measurement error with constant level
Fault description
Measured value
shows a too low or
too high level
0
time
Measured val-
ue jumps towards
100 %
0 time
48
Further comprehensive diagnostics options are available with a PC/
notebook with PACTware and the suitable DTM. In many cases, the
reasons can be determined in this way and faults rectified.
The below tables show typical examples of application-related
measurement errors with bulk solids. A distinction is made between
measurement errors during:
•
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.
1 Real level
2 Level displayed by the sensor
Note:
If the output level is constant, the cause could also be the fault setting
of the current output to "Hold value".
If the level is too low, the reason could be a line resistance that is too
high
Cause
Min./max. adjustment not correct
Incorrect linearisation curve
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. condensation, buildup); false
signal suppression no longer matches ac-
tual conditions
SITRANS LG260 - Operating Instructions
0
Rectification
Adapt min./max. adjustment
Adapt linearisation curve
Carry out a false signal suppression
Determine the reason for the changed false
signals, carry out false signal suppression,
e.g. condensation
1
2
time
PBD-51041061