FIXED READING
If the Reading is a fixed value, regardless of the transducer to material (object)
surface distance, ensure the:
1. Transducer acoustic beam is free from obstruction.
2. Surface monitored is not within the transducers’ nearest distance.
3. Transducer is not in contact with any metal object.
4. Material mixer (if used) is operating while the HYDRO+ is operating.
Check for (and remove if present) any acoustic beam obstruction.
If an obstruction cannot be removed or avoided, adjust the
TVT
(Time Varying
Threshold) Curve to reduce the Echo Confidence derived from the sound reflected by
the obstruction. (See Scope Displays, P810 and TVT Shaper, P832).
If the fixed Reading represents a distance within 2 metres (6 ft) from the transducer
face, ensure the material (object) surface is not within the Transducers’
nearest
distance
, (see INSTALLATION Transducer).
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, bevel the inside of the open end, or cut
the open end of the standpipe at a 45 angle.
For "ST-series" transducers
only, ensure non-metallic mounting hardware (supplied)
is used. Often, loosening overtightened mounting hardware will mechanically isolate
the transducer from a resonant metallic surface.
If difficulties persist, optimize transducer performance. Adjust Short Shot Frequency
(P842) and Long Shot Frequency (P843) for maximum Echo Confidence (P805).
If the preceding remedies have not produced satisfactory results, the false echo has
to be ignored. Extend Near Blanking (P800) to a distance (from the transducer face)
to just beyond the distance represented by the Reading. This also increases the
nearest distance the material level / object may come within the transducer face and
still be detected.
If increasing Near Blanking is unacceptable (the transducer cannot be mounted
higher) the TVT Curve must be raised in the area of the false echo.
Connect an oscilloscope to the HYDRO+, (see PARAMETERS Scope Displays,
P810). Adjust the TVT Start Min (P833), TVT Start Duration (P834), and TVT Slope
Min (P835) slightly.
Continue making minor TVT Curve adjustments and taking new measurements while
observing the Echo Marker position until the Echo Lock Window repeatedly locks onto
the true echo. Verify the false echo is still ignored, regardless of the vessel material
level, or empty / fill activity.
INSTALLATION
PARAMETERS
TROUBLESHOOTING
PL-507 159
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