Measurement Difficulties; Loss Of Echo (Loe); Loe Occurs When; If 2.4.3. Fail-Safe Ma Value Is Displayed, Check The Following - Siemens SITRANS LUT400 Operating Instructions Manual

11.6

Measurement Difficulties

If the LOE Timer (2.4.2.) (Page 175) expires due to a measurement difficulty, the Fail-Safe
mA Value (2.4.3.) (Page 175) displays. In rare cases, the SITRANS LUT400 may lock on to
a false echo and report a fixed or wrong reading.
11.6.1

Loss of Echo (LOE)

The Fail-Safe mA Value (2.4.3.) (Page 175) (seen in Current Output Value (2.5.8.)
(Page 179)) when the echo confidence is below the threshold value set in Echo Threshold
(2.12.2.2.) (Page 220).
11.6.1.1

LOE occurs when:

● The echo is lost and no echo is shown above the ambient noise (see Confidence
(3.2.9.2.) (Page 245) and Echo Strength (3.2.9.3.) (Page 245))
● Two echoes are too similar to differentiate (when BLF algorithm used) (see Confidence
(3.2.9.2.) (Page 245) and Echo Strength (3.2.9.3.) (Page 245))
● No echo can be detected within the programmed range (see Far Range (2.2.5.)
(Page 172))
11.6.1.2

If 2.4.3. Fail-Safe mA Value is displayed, check the following:

● Surface monitored is within the transducer maximum range
● Transducer (2.1.6.) (Page 170) model matches the transducer used
● Transducer is located and aimed properly
● Transducer (that is installed without a submergence shield) is not submerged.
11.6.2

Adjust Transducer Aiming

See the transducer manual for range, mounting, and aiming details. For optimum
performance, adjust transducer aiming to provide the best Confidence (3.2.9.2.) (Page 245)
and Echo Strength (3.2.9.3.) (Page 245) for all material levels within the measurement
range.
Displaying Echoes
The most efficient method of checking echoes is locally via the LUI, or remotely using
SIMATIC PDM, AMS, FC375/475, or DTM software.
Use LUI or remote software to graphically display the echo profile at the installation. Interpret
the echo profile and change relevant parameters. For LUI, see Requesting an Echo Profile
(Page 78) , and for details on how to interpret an Echo Profile, see Echo Processing
(Page 291).
SITRANS LUT400
Operating Instructions, 07/2019, A5E33329501-AC
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