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The
Global Water Flow Probe is a highly accurate
water velocity instrument for measuring flows
in open channels and partially filled pipes.
The water velocity probe consists of a protected
water turbo prop positive displacement sensor
coupled with an expandable probe handle ending
in a digital readout display. The water flow
meter incorporates true velocity averaging for
the most accurate flow measurements. The Flow
Probe is ideal for storm water runoff studies,
sewer flow measurements, measuring flows in
rivers and streams, and monitoring velocity
in ditches and canals.
Turbo-Prop
Sensor:
The Flow Probe incorporates the unique Turbo-Prop
propeller sensor that uses the most accurate
positive displacement technique for velocity
sensing. The Turbo-Prop is designed to shed
debris and is protected inside a 2" diameter
housing. The probe housing may be placed directly
on the bottom of pipes or streambeds for measuring
low flows down to 2" in depth. The flow
meter propeller rotates freely on its bearing
shaft with no mechanical interconnections for
minimal friction. Magnetic material in the propeller
tip passes the pickup coil in the housing producing
electrical impulses which are carried to the
readout display by an internal cable. The Turbo-Prop,
is easily removed for cleaning or replacement.
Digital
Readout Display:
The Digital Readout Display receives an electrical
signal from the propeller, amplifies the signal,
and converts the reading to feet per second
(or meters per second). The readout displays
instantaneous velocity and true average velocity.
The readout unit is water-resistant and incorporates
a unique two-button operation for changing functions
and zeroing the display. An internal watch type
battery powers the unit continuously for one
year and it is easily replaced. Also available
on the readout is maximum velocity, time-of-day
and stopwatch functions.
Probe
Handle:
The Flow Probe handle is telescoping and is
expandable from 3 feet to 6 feet in length (FP101)
or 5 feet to 15 feet (FP201). It is constructed
of anodized aluminum for light weight and long
life. The Flow Probe may be easily extended
up to 25 feet in length using standard PVC pipe
and an electrical extension cable. This allows
for sewer flow measurements from street level
and measuring of stream flows from low bridges.
A 3 ft. mylar coated staff gauge (graduated
in hundredths of a foot and centimeters) is
attached to the lower section of the water velocity
probe for instant water depth measurements and
accurate propeller positioning.
True
Velocity Averaging:
The Flow Probe uses true velocity averaging.
A running average is started once both buttons
are simultaneously pressed, this zeroes the
display, and when the water flow rate sensor
is placed into flowing water. As long as the
water velocity sensor remains in the flow, the
averaging continues. Once the average reading
becomes steady, the true average velocity has
been obtained. When you pull one of Global Water's
environmental flow meters from the water, the
average value is frozen on the display until
reset.
Flow
Measurement:
Flow is determined by V (average velocity) x
A (cross-sectional area)=Q (flow). The Area
of a channel is known for pipes, or is determined
for streams by measuring the distance from shore
and depth at various points across the flow
stream to construct the flow profile. The flow
monitor offers two unique methods for determining
the Average Velocity: 1) For small streams and
pipes, the flow velocity probe is moved smoothly
and uniformly throughout the flow profile. When
you see a steady average reading, the true average
velocity for the flow stream is obtained. 2)
For larger streams, the water flow meters may
be used to take a vertical profile of velocity
at several points across the stream, which then
become the average velocities for each of these
subsections of the flow stream.
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