Page 26 SITRANS Probe LU (HART) – OPERATING INSTRUCTIONS A5E32337695
Operation
7. Minimize false reflections (P838: Auto False-Echo Suppression Distance)
If SITRANS Probe LU displays an incorrect full level, or if the reading fluctuates between
a false high level and a correct level, you can use the TVT (Time Varying Threshold)
shaper parameters P838 and P837 together to prevent false-echo
1
detection. P837 and
P838 elevate the TVT in this region and de-sensitize the receiver from any ’base noise’
caused by internal transducer reflections, nozzle echoes, or other vessel false echoes.
Use P838 in combination with P837. Determine the actual distance from the transducer
face to the material surface. Subtract 0.5 m from this distance and enter the result,
following the Setup Instructions for P837.
1.
False echoes can be caused by obstructions within the beam path. For more detail, see TVT
adjustment parameters, page 60, and TVT curves, page 89.
Notes:
• This function works best when the vessel is empty or nearly empty: use it only if
there is a minimum distance of 2 meters from the transducer face to the material.
• Set P837 and P838 during start up, if possible.
• If the vessel contains an agitator, the agitator should be running.
Parameter Values
P838
Range
(depends on model
0.0000 to 6.00 m (20 ft) or
0.0000 to 12 m (40 ft)
Default 1.000 m (3.28 ft)
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