KROHNE BM 100A Handbook - Manual (Page 40)

40 Handbook BM 100 A
Configuration D
Parameters:
Function 1.1.1 = True tank height
Function 1.3.3 (4mA) = 0.0
Function 1.3.4 (20mA) = True tank height (1.1.1)
This combines examples B and C. Care must be taken when the product rises into the top dead zone
or drops into the bottom non-measurable zone as TDR gauges cannot monitor in these zones.
The configurations given above also apply when “distance” is selected in function 1.3.1 (after
adaptation of parameters entered).
*Factory configured probe length, L
1
, does include the Ø12mm x lg100mm(Ø0.5”xlg4”) weight for the
Ø8mm/0.3” single cable probe (type K).
Gauge operating logic when the reflection is lost
The product reflection pulse is usually lost when the level is in the top dead zone or near the bottom
of the tank. The diagram below shows the action taken by the gauge depending on where the last
reflection was lost.
Zone 1 : Dead zone
• Status marker 3 is displayed when the product enters the
dead zone.
• Gauge assumes the tank is full and displays the maximum
level value
Zone 2 : Full zone
• If the gauge loses the signal in this zone, it reacts as in zone
1 : the tank is assumed to be full.
• The gauge searches for a reflection in this zone.
• On reaching the full zone the level will continue to rise to a
current output of 20.5 mA (i.e. +3⅛%), if signal is not lost.
Note: the search zone increases to :
Fct. 1.1.2 “Hold Distance” + (Fct. 1.1.5 “Level Window”/2), if this
value is greater than 300mm / 12”.
Zone 3 : Central measurement zone
• The gauge uses Fct. 1.1.5 “Level Window” to search in this
zone for the largest pulse reflection.
• If the pulse is lost the reading freezes at the last value.
Status marker 3 will be displayed.
• Status marker 2 will then be displayed if no reflection is
found in the Level Window search zone, and the reflection
search will be enlarged to the probe length.
• The reading will remain frozen during this time.
Zone 4 : Empty zone
• If the reflection is lost in this zone, the gauge assumes the
tank / vessel to be empty.
• The short circuit reflection will become larger than product
reflection at this time.
• If level is not at zero, the gauge will descend further to a
level equivalent to a minimum output of 3.8 mA.
• The gauge searches for a reflection in this zone. The search
zone increases to:
Fct. 1.1.7 (Probe Length) – fct. 1.1.5 (Level Window)/2, if this
value is greater than 300 mm / 12”.