Siemens SITRANS LR250 Instruction Manual page 78

2.2.4.5.3. Noise Average
Displays the average ambient noise (in dB above 1 µV rms) of a noise
profile. Noise level is a combination of transient noise and receiving
circuitry. After a measurement, the values from the previous noise shot
will be displayed.
Open the menu View – Noise.
2.2.5. TVT (Auto False Echo Suppression) setup
Notes:
• If modifying these parameters via SIMATIC PDM, close all online windows.
• This function works best when the vessel is empty or nearly empty. Use it
only if there is a minimum distance of 2 meters from the radar instrument to
the material.
• Set Auto False Echo Suppression and Auto False Echo Suppression Distance
during startup, if possible.
• If the vessel contains an agitator, the agitator should be running.
First SITRANS LR250 learns the echo profile. Then the learned profile, or part of the
learned profile, is used to screen out false echoes. See Display before Auto False
Echo Suppression on page 75 for examples.
2.2.5.1. TVT Hover Level
Defines in percent how high the TVT (Time Varying Threshold) curve is placed
above the echo profile, with respect to largest echo. When SITRANS LR250 is
located in the center of the vessel, lower this parameter to prevent multiple
echo detections. (
Suppression
Values
2.2.5.6. Auto False Echo Suppression
Enables a 'learned' TVT curve to be used in place of the default TVT curve.
Options
Use this feature to ignore false echoes before the material echo. Set Auto
Suppression Range first. (See below for an illlustration.)
a.
b.
c.
d.
Page 74 SITRANS LR250 (HART) – INSTRUCTION MANUAL
For an illustration, see
Example after Auto False Echo Suppression
and
Rotate the instrument for best signal (lower false-echo amplitude).
Go to Range, and set the value (see
Suppression Range)
).
Open the menu Device – Auto False Echo Suppression and select
the option to change it.
Select Learn. The device will automatically revert to On (Use
Learned TVT) after a few seconds.
Display before Auto False Echo
Range: 0 to 100%
Default: 40%
0 Off
1 On (Enable Auto False Echo Suppression)
2 "Learn" the TVT curve
2.2.5.7. Range (Auto
, page 75)
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