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minimum range should be extended past the obstructions to eliminate the possibility of interference. Minimum
Range has a submenu; Manual.
MANUAL
Min Range Set sets the distance for the minimum range.
The defaults are:
— 12" (305 mm) for 56T-25 Transducers
— 24" (610 mm) for 56T-50 Transducers
72 MAXIMUM RANGE
Maximum Range displays and sets up the maximum range of operation. The maximum range is the farthest
distance from the face of the transducer where the transducer stops recognizing the return signal. Typically,
Maximum Range should extend past the bottom of the vessel to ensure that the SonoTracker Series displays
correct values when the level (or flow) is low. For level and differential level applications, the default Maximum
Range is 120% of the Span input in the Startup Procedure. For flow applications, the default Maximum Range is
120% of the Zero Distance input in the Startup Procedure.
Note: In Manual Mode, Max Range must be greater than Full Point + Span. The system will NOT allow a span
value that violates this distance. Change Max Range prior to changing Span.
73 SENTRY DSP™ (CONSULT BINDICATOR BEFORE MODIFYING!)
Extraneous noise caused by acoustical or electrical interference can cause changes in the SonoTracker Series
display, even though no material is moved. Sentry DSP™ helps to reduce the display changes that can result
from acoustical or electrical interference. The SonoTracker Series picks the level from the first echo as a
reference median; this is the value that is used in calculating the displayed level.
As shown in
, the SonoTracker Series then compares following signals to the reference median, and
Figure 26
recalculates the reference median when either of the following happen:
•
the number of successive signals above or below the median exceeds a triggering number
•
a signal falls outside of a user-defined window around the reference median.
When the SonoTracker Series recalculates the reference median, the displayed level changes to correspond
to the new reference median. Note that the Sentry DSP™ function affects setpoints, current output, and serial
output as well as the display. DSP has four submenus:
•
Qualify is the triggering number of successive signals above or below the median signal value, but within
the Step window. In example 2 shown in
the median value (but within the Step window) is detected, the SonoTracker Series moves the location of
the median value to that point or a percentage of the distance from the old median as determined by
DSPFact. This allows the SonoTracker Series to respond to definite trends in level changes. The default
for Qualify is 4.
•
Step Window is a window of equal height above and below the reference median. As shown in Figure 26,
SON280020 Rev. C
, Qualify is 3. When the third successive signal above
Figure 26
67
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