VEGA VEGAPULS 68 (≥ 2.0.0 - ≥ 4.0.0) Profibus PA - Manual (Page 59)

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9 Diagnosis, Asset Management and service
VEGAPULS 68 • Profibus PA
36537-EN-130205
•
Evaluation of fault messages, for example via the indicating and
adjustment module
•
Checking the output signal with 4 … 20 mA instruments
•
Treatment of measurement errors
Further comprehensive diagnostics options offer a PC with the soft-
ware PACTware and the suitable DTM. In many cases, the reasons
can be determined in this way and faults can be rectified.
The below tables show typical examples for application-relevant mea-
surement errors with bulk solids. There are two measurement errors:
•
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
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
2. 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 echoes, carry
out false signal suppression,
e.g. with condensation
Treatment of measure-
ment errors with bulk
solids