User's Manual

A5E32337685 SITRANS LR260 (PROFIBUS PA) – OPERATING INSTRUCTIONS Page 105
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D: Technical Reference
a low dK value, which may cause the vessel bottom to be reported as the level instead of
the actual material level, in low level conditions. CLEF range is the level below which the
CLEF algorithm will be used: above this level the Center algorithm is used.
Center of Mass selects the center of the echo for evaluation. Rising Edge selects the
rising edge of the echo. Hybrid uses a combination of Center and CLEF, depending on the
setting for CLEF range.
Auto False Echo Suppression
If an obstruction is causing a large echo before the material level echo, that echo will rise
above the default TVT curve and may be selected as the true echo. Auto False-Echo
Suppression modifies the TVT curve so that the false echo will not rise above the TVT
curve.
When you use Auto False Echo Suppression, the device first learns the echo profile at
that moment
1)
. A learned TVT curve follows the echo profile and rises above the false
echo. You set Auto Suppression Range so that the learned profile replaces the default
TVT curve up to a point past the obstruction. From that point on, the default TVT curve is
used. The material level echo rises above this, and is selected as the true echo.
Measurement Range
Near Range
2.2.3.5.1. Near Range programs SITRANS LR260 to ignore the zone in front of the antenna.
The default blanking distance is 50 mm (1.97") from end of horn antenna.
Near Range allows you to increase the blanking value from its factory default. But
2.2.4.3.
Auto False Echo Suppression (AUTO ECHO SUPP)
is generally recommended in
preference to extending the blanking distance from factory values.
1)
Use Auto False Echo Suppression when the material level is substantially lower than pro-
cess full level (ideally when the tank is empty or almost empty).
Example after Auto
False Echo Suppression
learned
TVT curve
level
Level (db)
false echo
echo marker