Function "Envelope Curve Display" (0E3) - Endress+Hauser HART Levelflex M FMP45 Operating Instructions Manual

Commissioning
50
6.6

Function "Envelope Curve Display" (0E3)

You can take the following information from the envelope curve display in this function:
level echo
full calibr.
echo threshold
envelope curve
minimum distance
of the plot
mapping
substracted signal
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.
Levelflex M FMP45 with HART/4...20 mA
interface echo
cursor
(electrical distance)
level echo
quality of
evaluated echo
cursor interface echo distance
(physikal distance, level
calculated with the aid
of the dc value)
empty calibr.
maximum distance
of the plot
probe length
L00-FMP4xIxx-07-00-00-en-004
Endress+Hauser