VEGA VEGAPULS 61 (≥ 2.0.0 - ≥ 4.0.0) Profibus PA - Manual (Page 58)

58
9 Diagnosis, Asset Management and service
VEGAPULS 61 • Profibus PA
36501-EN-121011
The below tables show typical examples of application-related meas-
urement errors with liquids. The measurement errors are differentiated
according to the following:
•
Constant level
•
Filling
•
Emptying
The images in column "Error pattern" show the real level with a bro-
ken line and the level displayed by the sensor as a continuous line.
1
2
Level
time 0
1 Real level
2 Level displayed by the sensor
Instructions:
•
Wherever the sensor displays a constant value, the reason could
also be the fault setting of the current output to "Hold value"
•
In case of a too low level indication, the reason could be a line
resistance that is too high
9.4 Measurement error with constant level
Fault description Error pattern Cause Rectification
1. Measured value
shows a too low or too
high level
Level
time 0
– Min./max. adjustment not
correct
– Adapt min./max. adjustment
– Wrong linearization curve – Adapt linearization curve
– Installation in a bypass tube or
standpipe, hence running time
error (small measurement error
close to 100 %/large error close
to 0 %)
– Check parameter "Application"
with respect to vessel form,
adapt if necessary (bypass,
standpipe, diameter)
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, product
type, dished end, high dielectric
figure, adapt if necessary
3. Measured value
jumps towards 100 % Level
time 0
– Due to the process, the ampli-
tude of the product echo sinks
– A false signal suppression was
not carried out
– Carry out false signal suppres-
sion
– Amplitude or position of a
false echo has changed (e.g.
condensation, buildup); false
signal suppression no longer
matches
– Determine the reason for the
changed false echo, carry out
false signal suppression, e.g.
with condensation
Treatment of measure-
ment errors with liquids