Congratulations on your purchase of the Global Water Flow
Probe. This instrument has been quality tested and
approved for providing accurate and reliable measurements.
We are confident that you will find the instrument to be a
valuable asset for your application. Should you require
assistance, our technical staff will be happy to help.
Table of Contents
I. Checklist
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Page 3
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II.
Inspection
III. Description
IV. General Instructions
V. Average Velocity
VI. Computer Operation
VII. Specifications •
VIII. Maintenance •
IX. Troubleshooting
X. Warranty
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17
XI. Appendix A: Calculations for Partially Filled Pipes 18
a. Flow Probe: FP111, FP211 or FP311
b. Flow Probe Computer
d. Carrying Case
c. Manual
II. Inspection
Your Flow Probe was carefully inspected and certified by our Quality
Assurance Team before shipping. If any damage has
during
shipping, please notify Global Water Instrumentation, Inc. and
occurred
file a claim with the carrier involved.
Use the checklist to ensure that you have received everything needed
to operate the Flow Probe.
III. Description
The Global Water Flow Probe is a rugged and highly accurate water
velocity instrument for measuring flows in open channels and partially
filled pipes. The water velocity probe consists of a protected
propeller and water bearing for measuring water velocity, coupled to
a telescoping probe handle ending in with a LCD display flow
computer. The Flow Probe is ideal for storm water runoff studies,
sewer flow measurements, measuring flows in rivers and streams,
and monitoring water velocity in ditches and canals.
Global
Water
800-876-1172 • globalw.com
4
The flow computer incorporates true velocity averaging for the most
accurate flow measurements. The computer’s primary display shows
the instantaneous velocity and is updated once per second. A
secondary display can be toggled between average velocity,
minimum or maximum velocity, and a timer than can be used to
measure the length of time in seconds that measurements are being
taken. A reset function allows the average, minimum and maximum
velocity measurements to be restarted; as well as resetting the timer
to zero. Up to 30 separate measurements of average, minimum and
maximum velocity can be stored in memory and viewed at any time.
Velocities can be displayed in both feet per second or meters per
second, a simple menu function allows you to switch between these
units at any time without changing previously stored data.
The flow probe computer is self contained and sealed. It has an
internal lithium battery that should last approximately 5 years
depending on use. The computer floats, and is shock and water
resistant for safe use in rugged wet environments.
IV. General Instructions
a. Remove any debris that may interfere with the flow
probe’s propeller. Make sure that the propeller turns
freely by blowing on it. Some chattering of the propeller
in air is normal, the bearing is designed to operate best
when wet.
b. Point the propeller directly into the flow you wish to
measure. Face the arrow inside the propeller housing
downstream. The FP111 probe handle is a two-piece rod
expandable from approximately 3’ to 6’, the FP211 is a
three-section rod expandable from 5’ to 15’, the FP311 is
a shorter version of the FP211 from 2.5’ to 5.5’. To
expand the rod for correct placement in flow, loosen the
locking nut on the handle. To aid in properly orienting the
flow probe inline with flow, an optional alignment fin is
available from Global Water, part number BA0210.
Global
Water
800-876-1172 • globalw.com
5
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,
any
button to restart the computer. Place the propeller at
press
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
800-876-1172 • globalw.com
6
V. Average Velocity
The Flow Probe is used to measure the average water velocity.
Stream flow velocity varies for several reasons:
a. The velocities vary throughout the flow’s
to the friction between the water and the channel. In
general, the velocities are greater in the center of the flow
and less near the bottom and sides of the channel.
b. The water surges in velocity with time. In a
running
stream, the velocity at a specific point can easily
vary 1-2 feet per second over the period of a minute. This
pulsating or surging of flow should be averaged to obtain
an accurate average flow reading (leave the probe in the
flow through a series of flow surges).
c. The water is not always moving in the same direction.
Even the smoothest water flow contains turbulence that
causes the water to move in different directions. These
velocity vectors not parallel to the flow will be seen as
moving slower because only a part of the vector parallel
to flow. Unlike other types of water velocity measuring
devices, the Global Water’s Flow Probe propeller’s
protective housing will channel the water parallel to flow
and help to eliminate errors caused by improperly
measuring velocity vectors not parallel to flow.
d. Large obstructions in the flow such as rocks and trees will
cause the water to flow around them, which may
flow to change direction for a short distance
the
obstructions. To properly measure the true water velocity,
the flow probe needs to be directly inline with the flow.
cross-section due
smooth
cause
from these
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