Endress+Hauser Levelflex M FMP40, Operating Instructions Manual

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Levelflex M FMP40 with HART/4...20 mA Commissioning
Hauser 55
6.6 Function "Envelope Curve Display" (0E3)
You can take the following information from the envelope curve display in this function:
L00-FMP4xIxx-07-00-00-en-004
The difference curve (substracted signal) is generated from the difference between the envelope
curve and the mapping, and is used to determine levels and for additional calculations.
6.6.1 Envelope curve
The Levelflex emits individual pulses in quick succession and scans their reflection with a slightly
variable delay. The energy values received are ordered by their time-of-flight. The graphic
representation of this sequence is known as an "envelope curve".
6.6.2 Mapping (empty curve) and difference curve
To suppress interference signals, the envelope curve is not directly evaluated in the Levelflex. The
mapping (empty curve) is first subtracted from the envelope curve.
The system looks for level echoes in the resulting difference curve.
Difference curve = envelope curve - mapping (empty curve)
The mapping (empty curve) should be a good representation of the probe and the empty tank or
silo. Ideally, only the signals from the medium being measured remain in the difference curve.
minimum distance
of the plot
maximum distance
of the plot
quality of
evaluated echo
empty calibr.
envelope curve
substracted signal
mapping
full calibr.
probe length
distance
level cursor interface echo
(physikal distance,
dc value)
calculated with the aid
of the
cursor
level echo
interface echo
(electrical distance)
level echo
echo threshold