water near the bottom of an open channel, but not at the bed
of the channel, to avoid accumulating debris. Its transducer
sensor is horizontally and vertically aligned with the flow.
For water depth measurement, STARFLOW uses a solid state
pressure sensor mounted underneath. STARFLOW has a
water depth measurement range of 0 to 5 meter. Its accuracy
is ±0.25% of the workable range. This equipment runs on
the power of 12 volts DC source. STARFLOW also has an
additional ability to measure water velocity using Doppler
shift where the frequency of the sound reflected from a
moving target is varied by the velocity of the target, that is,
STARFLOW uses the in-water particles moving in an open
channel as its reflective targets in order to measure water
velocity. The measurement range is 21mm/s to 4500mm/s
bidirectional with resolution of 1mm/s and accuracy of 2%.
In our measurement, we notice that STARFLOW is quite
sensitive to water velocity fluctuations in the channel. As a
result, continual velocity logging with a STARFLOW will
show cycles of velocity fluctuation. In order to attenuate the
effect of short period fluctuation cycles and obtain more
accurate data, we use the average velocity over a time
interval instead of raw measured data. With water velocity
and cross sectional data of installed open channel, flow rate
can be calculated. STARFLOW is connected to GDU via
RS-232 and Serial Data Interface at 1200 baud (SUI-12)
communications. When the water information is acquired
through the sensor, it will be transmitted to the GDU for data
processing and then data transmission via the mobile GPRS
communication tunnel to the control center.