Milltronics AiRanger SPL PL-573, Instruction Manual

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PL-573 AiRanger SPL Page 105
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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 such that the SPL "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 SPL is operating.
If the fixed Reading represents a distance more than 3 metres (9 feet) from the
transducer face, the SPL is probably detecting some vessel interior obstruction. Aim
away from (or remove) the obstruction.
If the obstruction cannot be removed or avoided, the SPL 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), 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).