66
9 Diagnosis, asset management and service
NCR-84 Two-wire 4 … 20 mA/HART
51141-EN-181127
Fault description
Cause
Rectification
2. Measured value
jumps towards 0 %
Level
time
0
•
Multiple echo (vessel top, product
surface) with amplitude higher than the
level echo
•
Check parameter "Application", especially
vessel top, type of medium, dished bot-
tom, high dielectric constant, and adapt if
necessary
3. Measured val-
ue jumps towards
100 %
Level
time
0
•
Due to the process, the amplitude of the
level echo sinks
•
A false signal suppression was not carried
out
•
Carry out a false signal suppression
•
Amplitude or position of a false signal has
changed (e.g. condensation, buildup);
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
Measurement error during filling
Fault description
Cause
Rectification
4. Measured value
remains unchanged
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 measurement situation: Antenna
must protrude out of the socket, instal-
lations
•
Remove contamination on the antenna
•
In case of interferences due to installa-
tions in the close range: Change polarisa-
tion direction
•
Create a new false signal suppression
•
Adapt max. adjustment
5. Measured value
remains in the bot-
tom section during
filling
Level
time
0
•
Echo from the tank bottom larger than the
level echo, for example, with products with
ε
r
< 2.5 oil-based, solvents
•
Check parameters Medium, Vessel height
and Floor form, adapt if necessary
6. Measured value
remains momentar-
ily unchanged during
filling and then jumps
to the correct level
Level
time
0
•
Turbulence on the product surface, quick
filling
•
Check parameters, change if necessary,
e.g. in dosing vessel, reactor
925-0373 Rev A