VEGA VEGAFLEX 86 4 … 20 mA_HART two-wire Coax probe With SIL qualification - Manual (Page 69)

69
10 Diagnostics and service
VEGAFLEX 86 • 4 … 20 mA/HART two-wire
44231-EN-130823
Measurement error with constant level
Fault description Error pattern Cause Rectification
1. Measured value
shows a too low or too
high level
Leve
l
time 0
– Min./max. adjustment not
correct
– Adapt min./max. adjustment
– Wrong linearization curve – Adapt linearization curve
– Running time error (small
measurement error close to
100 %/serious error close to
0 %)
– Repeat setup
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 a false signal sup-
pression
– Amplitude or position of a
false signal has changed (e.g.
buildup); false signal suppres-
sion no longer matches
– Determine the reason for the
changed false signals, carry out
false signal suppression, e.g.
with buildup
Measurement error during filling
Fault description Error pattern Cause Rectification
3. Measured value re-
mains in the area of the
bottom during filling
Leve
l
time 0
– Echo from the probe end larger
than the product echo, for
example, with products with
ε
r
< 2.5 oil-based, solvents, etc.
– Check parameter "Medium"
and "Vessel height", adapt if
necessary
4. Measured value re-
mains momentarily
unchanged during fill-
ing 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 ves-
sel, reactor
5. Measured value
jumps sporadically to
100 % during filling
Leve
l
time 0
– Changing condensation or
contamination on the probe
– Carry out a false signal sup-
pression
6. Measured value
jumps to ≥ 100 % or
0 m distance
Leve
l
time 0
– Level echo is no longer
detected in the close range
due to false signals in the close
range. The sensor goes into
overfill protection mode. The
max. level (0 m distance) as
well as the status message
"Overfill protection" are output-
ted.
– Eliminate false signals in the
close range
– Check installation conditions
– If possible, switch off the func-
tion "Overfill protection"