Reducing Acoustical Noise; Measurement Difficulties; Loss Of Echo (Loe); Adjust Transducer Aiming - Siemens SITRANS LUT400 Operating Instructions Manual

Reducing Acoustical Noise

• Move the transducer away from the noise source.
• Use a stilling well.
• Install a rubber or foam bushing or gasket between the transducer and the
mounting surface.
• Relocate or insulate the noise source.
• Change the frequency of the noise. Ultrasonic devices are sensitive to noise in the
frequency range of the transducer employed.
• Check that transducer is not mounted too tightly; only hand-tight.

Measurement Difficulties

2.4.2. LOE Timer
If the
Value
displays. In rare cases, the SITRANS LUT400 may lock on to a false echo and report
a fixed or wrong reading.

Loss of Echo (LOE)

2.4.3. Fail-Safe mA Value
The
confidence is below the threshold value set in
LOE occurs when:
• The echo is lost and no echo is shown above the ambient noise (see low
Confidence
• Two echoes are too similar to differentiate (when BLF algorithm used) (see low
3.2.9.2. Confidence
• No echo can be detected within the programmed range (see
If 2.4.3. Fail-Safe mA Value is displayed, check the following:
• Surface monitored is within the transducer maximum range
2. 1 .6. Transducer
•
• Transducer is located and aimed properly
• Transducer (that is installed without a submergence shield) is not submerged

Adjust Transducer Aiming

See the transducer manual for range, mounting, and aiming details. For optimum
performance, adjust transducer aiming to provide the best
Echo Strength
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" on page 57, and for details on how to interpret an Echo Profile, see "Echo
Processing" on page 257.
Page 244 SITRANS LUT400 (HART) – OPERATING INSTRUCTIONS
expires due to a measurement difficulty, the
displays (seen in
3.2.9.3. Echo Strength
and low
3.2.9.3. Echo Strength
and low
model matches the transducer used
2.4.3. Fail-Safe mA
2.5.8. Current Output Value
2.12.2.2. Echo Threshold
)
)
2.2.5. Far Range
3.2.9.2. Confidence
) when the echo
.
3.2.9.2.
).
3.2.9.3.
and
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