User's Manual

Appendix A: Technical reference
A.2 Echo processing
SITRANS LR250 (PROFIBUS PA)
Operating Instructions, 01/2014, A5E32221386-AB
207
A.2.6
Auto False Echo Suppression
Note
•
For detailed instructions on using this feature via PDM see Auto False Echo Suppression
(Page 73).
•
For detailed instructions on using this feature via the handheld programmer see
Auto
False Echo Suppression (2.5.10.1.).
Auto False Echo Suppression is designed to learn a specific environment (for example, a
particular vessel with known obstructions), and in conjunction with Auto False Echo Suppression
Range to remove false echoes appearing in front of the material echo.
The material level should be below all known obstructions at the moment when Auto False Echo
Suppression learns the echo profile. Ideally the vessel should be empty or almost empty, and if
an agitator is present, it should be running.
The device learns the echo profile over the whole measurement range and the TVT is shaped
around all echoes present at that moment.
Auto False Echo Suppression Range (2.5.10.2.)
Auto False Echo Suppression Range specifies the range within which the learned TVT is
applied. Default TVT is applied over the remainder of the range.
The learned TVT screens out the false echoes caused by obstructions. The default TVT allows
the material echo to rise above it.
Auto False Echo Suppression Range must be set to a distance shorter than the distance to the
material level when the environment was learned, to avoid the material echo being screened out.