Siemens sitrans LU01 - Manual (Page 108)

Page 102 SITRANS LU01 – INSTRUCTION MANUAL 7ML19985BE02
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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 SITRANS LU01, ( 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.
Wrong Reading
If the Reading is erratic, or jumps to some incorrect value periodically, ensure the:
1. Material (object) surface monitored, is not beyond the transducers maximum range.
2. Material is not falling in the transducer sound beam.
3. Material (P002) value matches the material monitored.
4. Measurement Response (P003) is not set too fast.
5. Transducer (P004) type entered matches the transducer used.
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 material/object monitored is outside this
distance, increase Range Extension (P801) as required.
If the material monitored is a liquid, check for splashing in the vessel. Decrease
Measurement Response (P003) as required to stabilize the Reading, or install a stilling
well (contact Milltronics or your local distributor).
Access the Noise (P807) parameter. If the peak value jumps wildly, verify the transducer
cable shields are connected to the SITRANS LU01 shield terminals and not to ground
elsewhere.
If the SITRANS LU01 is mounted in close proximity to (or transducer cables run near
those of) another ultrasonic level monitor, see Level System Sync (P726).
Temporarily disable nearby SCR control drives, high voltage or current contactors. If the
condition disappears, move the SITRANS LU01 to another location.
Set Echo Lock (P711) to "max verification" (response to material level changes may be
slowed somewhat).