Global Water FP111 User Manual page 5

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c. To extend battery life, a low power mode is incorporated
that will take effect after 5 minutes of inactivity. If the
propeller is stopped and none of the pushbuttons are
pressed for 5 minutes, this mode will take effect and the
velocity displays will go blank. Press any of the 4
pushbuttons to start the computer back up for taking
measurements or viewing stored data.
d. To make a measurement, make sure that the computer is
not in low power mode by confirming that the velocity
displays are shown. If these displays are blank, press
any button to restart the computer. Place the propeller at
the desired measuring point and press the RESET button
to begin taking new average, minimum and maximum
readings. If you do not reset this data, the minimum
reading will be zero and the average will include all zero
readings since the last reset. The measurements are
updated once per second. Pressing RESET before
beginning a measurement is required for best accuracy.
e. To determine flow from the velocity data, measure or
calculate the cross-sectional area of your flow stream in
square feet (or square meters when taking measurements
in m/s). If you are measuring flow in round pipes,
measure the depth of water and pipe diameter, then use
the enclosed tables to determine cross-sectional area
(see Appendix A: Calculations for Flow in Partially Filled
Pipes). If you are measuring flow in another channel
type, manually measure water depth at several points
across the flow. These measurements are most easily
recorded by drawing a diagram on graph paper with a
scale of 1 square foot (or meter) per graph paper square.
Cross-sectional area (in square feet or meters) can then
be found by counting the number of squares in the
stream.
f. The average velocity times the cross-sectional area
equals flow or Q = V x A; where velocity is in FT/S and
area is in FT² (or M/S and M²)
g. If the propeller gets fouled while measuring flow, clean it
until the prop turns freely and start over.
Global Water
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