Siemens SITRANS L Operating Instructions Manual page 179

Position Detect (2.5.7.2.)
The echo position detection algorithm determines which point on the echo will be used to
calculate the precise time of flight, and calculates the range using the calibrated propagation
velocity (see Propagation Factor (2.5.3.) for values). There are three options:
• Center
• Hybrid
• CLEF (Constrained Leading Edge Fit)
Center
Uses center of the echo.
Hybrid
Uses the Center algorithm for the top part of the vessel, and the CLEF algorithm for the part
nearest the vessel bottom, according to the setting for CLEF range.
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.
SITRANS LR200 with PROFIBUS PA
Operating Instructions, 07/2021, A5E32337680-AF
Technical reference
C.3 Echo processing
179