Siemens SITRANS F Operating Instructions Manual page 159

Section 2
Check actual transducer spacing matches "Ltn" dimension.
Verify that Signal Graph is acceptable (see below).
Use recommended High Precision or first recommended Universal Transducer.
Verify Liquid Vs in database (take into account actual temperature & pressure).
Verify Liquid chemistry is as expected. (Ask about additives, Pressure, Temp.)
Try "1-Cycle" Vs Correction in Diagnostics if error remains for a liquid with well defined Vs
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data
Low Valc
Clean and condition pipe surface.
Use High Precision or first recommended Universal Transducer.
Use Direct Mount (be sure of transducer 180º alignment!).
Use larger size transducer (Universal Only!).
Use wider spacing (Maximum or Letter D).
Stop flow to check for Aeration/Cavitation.
Try another location.
Perform an Initial Makeup after ANY of the above changes!!
Detection Fault/Low Signal
Perform all checks for "Low Valc"
Ensure pipe is full.
Ensure cables are terminated at both ends; Check continuity with Ohmmeter.
Check operation on Pipe Simulator.
Switch off any radiating electrical equipment in area (Transmitters, Variable Freq. Drives, etc.).
High Vaer
Avoid transducer mounting near flow obstructions.
Check for possible pressure drop sources (Pipe Expansion, Orifice, Check Valve, etc.).
Check liquid "Flash Point" against application conditions.
Pinch downstream valve (of Transducer) to raise pressure.
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1010PFM-3G