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7ML19985LT01 SITRANS LR560 (PROFIBUS PA) – OPERATING INSTRUCTIONS Page 117
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D: Technical Reference
CLEF (Constrained Leading Edge Fit)
Uses the leading edge of the echo.
Is used mainly to process the echo from materials with a low dK value.
In an almost empty flat-bottomed vessel, a low dK material may reflect an echo weaker
than the echo from the vessel bottom. The echo profile shows these echoes merging. The
device may then report a material level equal to or lower than empty
The CLEF algorithm enables the device to report the level correctly.
Example: CLEF off: Position set to Hybrid
Example: CLEF enabled
default TVT
vessel
bottom
echo
selected
material
echo
echo marker
Vessel height: 1.5 m; CLEF range set to 0 (Center algorithm gives the same result.)
default TVT
vessel
bottom
echo
material
echo
selected
echo marker
Vessel height: 1.5 m; CLEF range set to 0.5 m