Page 44 SITRANS LR250 (PROFIBUS PA) – INSTRUCTION MANUAL 7ML19985JF02
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SIMATIC PDM
Auto False Echo Suppression
If you have a vessel with known obstructions, we recommend using Auto False Echo
Suppression to prevent false echo detection. This feature can also be used if the device
displays a false high level, or the reading is fluctuating between the correct level and a
false high level.
The device learns the echo profile over the whole measurement range and the TVT is shaped
around all echoes present at that moment. (See
Auto False Echo Suppression (2.2.4.2.)
on
page 114 for a more detailed explanation.)
The learned TVT will be applied over a specified range. The default TVT is applied over the
remainder of the measurement range.
1) Determine Auto Suppression Range. Measure the actual distance from the sensor
reference point to the material surface using a rope or tape measure. Subtract 0.5 m
(20") from this distance, and use the resulting value.
Notes:
• Make sure material level is below all known obstructions at the moment Auto False
Echo Suppression is used to learn the echo profile. An empty or almost empty vessel
is recommended.
• Note the distance to material level and set Auto Suppression Range to a shorter
distance to avoid the material echo being screened out.
• Set Auto False Echo Suppression and Auto Suppression Range during startup, if
possible.
• If the vessel contains an agitator it should be running.
• Before adjusting these parameters, rotate the instrument for best signal (lower
false-echo amplitude).
Before Auto False Echo
Suppression
After Auto False Echo
Suppression
learned TVT
default TVT
default
TVT
range
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