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 DPL+ is operating.
If the fixed Reading represents a distance more than 3 metres (9 feet) from the transducer face, the DPL+ is
probably detecting some vessel interior obstruction. Aim away from (or remove) the obstruction.
If the obstruction cannot be removed or avoided, the DPL+
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).
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) see Auxiliary
Transducer (P725). Otherwise, the TVT Curve must be raised in the area of the false echo.
Connect an oscilloscope to the DPL+, ( see ENHANCEMENT 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.
ENHANCEMENT PARAMETERS
ENHANCEMENT PARAMETERS
INSTALLATION
ENHANCEMENT PARAMETERS
TROUBLESHOOTING GUIDE
PL-508 99
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