Dynasonics D300_301 Series Doppler Ultrasonic Flow Meter - Manual (Page 6)

Rev. 2/00 -1.5- 300/301
The flowmeter is typically used as a unidirectional
meter and is most accurate when the transducer is
mounted in the orientation detailed in this manual.
But, the meter will measure flow in both directions —
although flow direction will not be indicated or
totalized properly. The flowmeter will operate from
signals returned from turbulence alone (such as
installation directly at pump discharges or
downstream from elbows and valves); however, it
should be noted that turbulence may vary with flow
rates and result in non-linear results. The
repeatability of the device is not dependent on most
process liquids.
The flowmeter is designed to measure the flow of
liquids and slurries, as long as a small, homogeneous
quantity of entrained air or suspended solids are
present. Without the presence of continuing supply of
air or solids, the transmitted pulses are not reflected
back to the transducer and the indicator will indicate
zero flow. Also, the LED signal indicator will be
extinguished.
The signal strength light will indicate (continuously
blink) when a minimum size and concentration of
suspended particles are available for a reliable flow
reading (100 micron and 100 PPM minimum) and the
liquid is moving at least 0.1 FPS [0.03 MPS]. Most
water-based liquids can be measured from a factory
calibrated flowmeter. However, liquids with a heavy
solids level (i.e. over 2%), liquids with sound speeds
that vary from water (see Appendix of alternate
liquids list) or pipes with liners may have to be field
calibrated. This is done by adjusting the span pot
(R30 on circuit board) to make the indicator agree
with a known flow velocity or a mathematically
corrected fluid velocity. All standard indicator scales
are calibrated to customer specified units. If the scale
range or units need to changed, the process to do so
is covered in detail later in this manual.
PART 1 - GENERAL
Measuring Limits