38
11 Diagnostics and servicing
VEGAPULS 21 • Two-wire 4 … 20 mA/HART
58351-EN-191014
11.5 Treatment of measurement errors
The tables below give typical examples of application-related meas-
urement errors.
The images in column "
Error description
" show the actual level as a
dashed line and the output level as a solid line.
1
2
Level
time
0
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
Liquids: Measurement error at constant level
Fault description
Cause
Rectification
Measured value shows a too
low or too high level
Level
time
0
Min./max. adjustment not correct
Adapt min./max. adjustment
Incorrect linearisation curve
Adapt linearisation curve
Measured value jumps to-
wards 100 %
Level
time
0
Due to the process, the amplitude of the
level echo sinks
A false signal suppression was not car-
ried out
Carry out a false signal suppression
Amplitude or position of a false signal
has changed (e.g. condensation, build-
up); false signal suppression no longer
matches actual conditions
Determine the reason for the changed
false signals, carry out false signal sup-
pression, e.g. with condensation.
