Siemens sitrans LU01 - Manual (Page 107)

7ML19985BE02 SITRANS LU01 – INSTRUCTION MANUAL Page 101
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If a discernible echo is observed (representative of the material/object surface), reduce
the Confidence Threshold (P804) while taking new measurements (in the RUN or
PROGRAM mode).
Sometimes, material simply cannot be detected during vessel filling. In these cases, set
up failsafe operation so the SITRANS LU01 anticipates the rate of material level increase
and adjusts the reported Reading accordingly. This operation is reliable, as long as when
the dust (or foam) settles a valid echo can be received. See Technical Reference
Application Examples \ Example 1 - Level Measurement.
Fixed Reading
If the Reading is a fixed value, regardless of the transducer to material (object) surface
distance, ensure the:
1. Transducer sound beam is free from obstruction.
2. Material (object) surface monitored is not within the Transducers' nearest
measurable distance.
3. Transducer is not in contact with any metal object.
4. Material agitator (if used) is on while the SITRANS LU01 is operating.
If the fixed Reading represents a distance more than 3 metres (9 feet) from the transducer
face, the SITRANS LU01 is probably detecting some vessel interior obstruction. Aim away
from (or remove) the obstruction.
If the obstruction cannot be removed or avoided, the SITRANS LU01 TVT (Time Varying
Threshold) Curve must be modified to reduce the Echo Confidence derived from the
sound reflected by the obstruction. (See Enhancement Parameters Scope Displays, P810
and TVT Shaper, P832).
If the fixed Reading represents a minimal distance from the transducer face, the condition
may be caused by a sound beam obstruction (check for this first), but could also be due to
other factors.
If the material (object) surface is within the Transducers' nearest distance (see
Installation/Transducer Mounting on page 10), mount the transducer higher above
(farther away from) the nearest object to be monitored.
If the transducer is mounted on a standpipe, grind smooth any burrs or welds on the
inside or
open end (the end that opens into the vessel). If the problem persists, install a
larger diameter or shorter length standpipe, or flare (increase the diameter of) or cut the
open end of the standpipe at a 45° angle.
For ST-series transducers only, ensure the non-metallic mounting hardware (supplied) is
used. Often, loosening over tightened mounting hardware will mechanically isolate the
transducer from a resonant metallic surface.
Regardless of the mounting type, if difficulties persist, optimize the Transducer operating
frequencies (see Enhancement Parameters Short Shot Frequency (P840) and Long Shot
Frequency (P841).