Siemens SITRANS LUT400, Operating Instructions Manual

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Page 244 SITRANS LUT400 (HART) – OPERATING INSTRUCTIONS A5E33329501
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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
If the
2.4.2. LOE Timer
expires due to a measurement difficulty, the
2.4.3. Fail-Safe mA
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)
The
2.4.3. Fail-Safe mA Value
displays (seen in
2.5.8. Current Output Value
) when the echo
confidence is below the threshold value set in
2.12.2.2. Echo Threshold
.
LOE occurs when:
• The echo is lost and no echo is shown above the ambient noise (see low
3.2.9.2.
Confidence
and low
3.2.9.3. Echo Strength
)
• Two echoes are too similar to differentiate (when BLF algorithm used) (see low
3.2.9.2. Confidence
and low
3.2.9.3. Echo Strength
)
• No echo can be detected within the programmed range (see
2.2.5. Far Range
).
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
model matches the transducer used
• 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
3.2.9.2. Confidence
and
3.2.9.3.
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.