KROHNE BM 102 Handbook - Manual (Page 35)

BM 102 35
Dead zone: configuration of user menu PCSTAR 2 function 1.1.2 (HART
® Fct. 2.1.1.4)
The top dead zone is the minimum measuring distance between the gauge flange facing (the
reference point) and the product. The various probes for the BM 102 have differing top dead
zones and these are given in section 5.2.3: Probe measurement limits.
Why is configuration of the dead zone important?
The gauge will not display measurements taken here – the reading is blocked on reaching this
zone. This will avoid the gauge confusing the true level with a parasite (i.e. flange) as the product
nears the tank fitting and thereby displaying a false reading. It should be noted that although the
reading is frozen, the gauge will continue to follow the reflection. The PCSTAR 2 F8-marker menu
will display “Tank full” in this zone.
What is the difference between these functions:
PCSTAR 2 Fct 1.1.2/ HART
®
Fct. 2.1.1.4: Dead zone
PCSTAR 2 Fct 1.5.1/ 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 PCSTAR 2 F8-marker menu will display “Tank full” and “Level lost” in this
zone. This is illustrated below – the value in the box is the displayed value:
1 Height of tank fitting
2 Detection delay
(Fct.1.5.1=120mm)
3 Dead zone limit
(Fct.1.1.2=150mm)
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) = 8850 mm - dead zone configured limit in terms of level