Siemens interranger DPS300 Instructional Manual page 104

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 sludge surface is within the Transducers' nearest distance, limit the high
level of the sludge blanket.
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 sludge may come within the transducer face and still be
detected.
Connect an oscilloscope to the DPS300, (see ENHANCEMENT PARAMETERS /
Scope Displays, P810). Adjust the TVT Start Min (P833), TVT Start Duration
(P834), and TVT Slope Min (P835) slightly, to raise the TVT curve in the area of
the false echo.
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
sludge level, or empty/fill activity.
Wrong Reading
If the Reading is erratic, or jumps to some incorrect value periodically, ensure the:
1. Sludge level is not beyond the transducers maximum range.
2. Material (P002) value matches the type of sludge monitored.
If the periodic incorrect value is always the same, see Fixed Reading. If the
incorrect value seems to be random, verify the material surface to transducer
distance is less than the Empty value entered plus 20%. If the sludge monitored is
outside this distance, increase Range Extension (P801) as required.
Variable Reading
If the material reading is "jumping" from the correct level, try the following
techniques:
•
Set the Long Shot Number (P841) to a larger value to average more shots to get a
measurement
•
Set Echo Lock (P711) to "max verification" (response to sludge level changes may
be slowed somewhat).
•
Increase the Echo Lock Sampling (P712) and / or decrease the Echo Lock
Window (P713) to ignore erroneous readings
•
Decrease the Long Shot Width (P845) to keep the different echos in the profile
distinct
Access the Noise (P807) parameter. If the peak value jumps wildly, verify the
transducer cable shields are connected to the DPS300 shield terminals and not to
ground elsewhere.
InterRanger DPS300
104
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