Fuji Electric FSJ Instruction Manual page 122

(2) Diagnosis of wave receipt fluctuation
Splash (foreign material) contamination → If measurement is normal after stopping flow, there is a high possibility of splash
(foreign material) contamination, and this must be eliminated.
• Cover the pipe at detector mounting locations, and the detector with thermal insulating material.
• If there are any parts of the upstream pipe with no thermal insulating material, cover those parts with thermal insulating
material.
• Relocate the detector to drainage discharge locations (steam traps) and the separator downstream.
• Install drainage discharge locations (steam traps) and a separator at the detector upstream side to eliminate splashes.
(3) Noise diagnosis
Mounting failure of noise elimination frame
Connector contact defect
The double-sided tape on the noise elimination frame is
peeled off, or the heat-resisting rubber is damaged.
Noise in power line
The detector is not grounded, or grounding is insufficient.
If there is noise in the ground line (panel grounding, etc.)
The dedicated signal cable is picking up inductive noise.
The piping outer diameter differs from the specification
and the noise elimination frame is not closely attached to
the piping.
Specification: ø 60.5 mm (50 A), ø 76.3 mm (65 A),
ø 89.1 mm (80 A), ø 114.3 mm (100 A)
Cause
Follow the procedure in "5.4 Mounting the noise
elimination frame" again.
5.8 Carry out Wiring connection over again.
Replace the double-sided tape or prepare/replace the
heat-resisting rubber in accordance with "5.10
Precautions for removing the noise elimination frame".
Install a noise-cut transformer.
Check the external grounding terminal (M4) grounding
(Class D) condition described in section 3.4.4 Wiring to
each terminal.
Try disconnecting the ground wire.
Separate the dedicated signal cable from the power
cable. Use a short, dedicated cable.
Check the piping outer diameter.
Install the device again to a place where the outer
diameter specification is satisfied.
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Remedy