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Dead zone: configuration of user menu EView2 – Dead zone (P06)
parameter function (HART® Fct. 2.1.1.4)
The top dead zone is the minimum measuring distance between the
surface of the gauge flange (the reference point) and the measured
medium.
The various probes designed for MicroTREK have differing top dead
zones and these length data are given in the “Technical data of the
probes” chart in “3. Technical data” section
The importance of the dead zone configuration.
Limits of probe measuring ranges
The gauge will not display measurements taken in the dead zone –
Entering the dead zone, the device disables the display.
This will avoid the gauge confusing the true level with a false reflection,
corrupts the measurement (i.e. flange) as the medium nears the tank
fitting and thereby displaying a false reading. It should be noted that
although the reading is not displayed-, the gauge will continue to follow
the reflection.
In EView2, the “Tank Full” status indication can be continuously
monitored during polling on the device status window or on the “Markers
diagram”.
What is the difference between these functions?
EView2 – Dead zone (P06) / HART
®
Fct. 2.1.1.4: Dead zone, EView2 –
Detection delay (P08) / HART
®
Fct. 2.1.5.3: Detection delay
The “detection delay” function masks all signals (i.e. none are detected
by the gauge) up to a defined distance from the flange facing. The
“detection delay” zone size is never greater than the “dead zone” size.
The EView2 „device status” menu will display “Tank full” and “Level lost”
in this zone.
This is illustrated below – the value in the box is the displayed value:
level/mm
No level reflection inside detection delay zone
V/V
8850mm(3)
8850mm
2 3
9
level/mm
Level reflection inside dead zone
V/V
8850mm(3)
8850mm
2 3
8
level/mm
Level reflection outside dead zone
V/V
8850mm(3)
8600mm
2 3
7
4
5
6
1
Height of tank fitting
2 Detection
delay
(Detection delay = 120 mm [4.72 inch])
3
Dead zone limit (Dead zone = 150 mm [5.9 inch])
4 Emitted
signal
5
Flange reflection (masked)
6
Masked zone (all signals here are ignored)
7
Level reflection outside dead zone – true level displayed
8
Level reflection inside dead zone – level at dead zone limit displayed (frozen)
9
Level reflection inside detection delay zone – not detected by gauge and level
at dead zone limit displayed (frozen)
*(3) = 985 mm (38.8 inch) Dead zone configured limit in terms of level