30
10 Diagnostics and servicing
VEGAPULS C 21 • SDI-12
58342-EN-200121
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.
Liquids: Measurement error during filling
Fault description
Cause
Rectification
Measured value remains un-
changed during filling
Level
time
0
False signals in the close range too big
or level echo too small
Strong foam or spout generation
Max. adjustment not correct
Eliminate false signals in the close
range
Check measuring point: Antenna should
protrude out of the threaded mounting
socket, possible false echoes through
flange socket?
Remove contamination on the antenna
In case of interferences due to instal-
lations in the close range, change
polarisation direction
Create a new false signal suppression
Adapt max. adjustment
