Dwyer PSX2 - Manual (Page 158)

149
State Cause Remedy
Measured value is not
zero though water fl ow
has stopped.
• Water is subjected to convection in
a pipe. Ö Normal
• Zero adjustment has been per-
formed. Ö • Perform zero adjustment
again after making sure water
fl ow has stopped completely.
• When water fl ow stops, pipe is not
fi lled up with water or becomes
empty. Ö • The measured value, just
when ultrasonic wave cannot
be propagated, is held.
Ö Normal
Measured value has an
error.
• Input piping specifi cations are dif-
ferent from actual ones.
Ö
• A difference of 1% in inner
diameter causes an error of
about 3%.
Ø
• Input specifi cations correctly.
• Input scale as lining. • Because of an old pipe, scale has
stuck. Ö
The length of straight pipe portion
is inadequate. Ö Select a different location of
sensor mounting (move the up-
stream side of a fl ow disturbing
element).
10D and 5D are required at least
on the upstream and downstream
sides.
Flow disturbing element should
not be present within 30D on
upstream side.
Pump, valve, fl ow joining pipe or
the like is unallowable.
• Mount the sensor at differ-
ent angles with respect to the
cross section of pipe to fi ne
the location where mean value
is obtainable. The mount the
sensor at that location.
• Pipe is not fi lled with water or mud
and sand have precipitated. Ö Precipitation is more when
the cross section of pipe has a
smaller area.
Ø
Shift the sensor to the vertical
portion of pipe.
Flow velocity profi le is
not available.
No refl ector in the fl uid or weak
refl ection. Ö Measure in a place subject to
refl ector.
Low fl ow velocity. Ö Increase fl ow velocity.
Bulletin F-9-PUX2