The Sigma 920 Area Velocity Flow Meter can be used
in portable or permanent applications and is available with up to two
independent level/velocity channels. You can measure level and velocity
in two channels or velocity in one and level in another. And, With
American Sigma´s pager communication, you can be alerted to overflows,
bypasses, or a change in the flow pattern. Choose from submerged
pressure transducer/velocity sensor or American Sigma In-Pipe Ultrasonic
Depth Sensor combined with a "wafer-thin" velocity sensor that provides
greater accuracy in shallow flows.
Multiple sensors for redundancy, averaging and
multiple pipe monitoring.
Easy installation with fast setup and no velocity
calibration required.
Sampler pacing capabilities, ideal for CSO and
storm water.
Optional rainfall logging feature records and
characterizes rain events, a true innovation in water monitoring.
NEMA 6P sealed to withstand submergence and
prolonged surcharge conditions
Low power draw creates an extended 90-day battery
life.
Advanced, ultrasonic one-MHz Doppler technology
avoids signal dropouts and ensures, high levels of accuracy in
low-flow, full-pipe, or reversed-flow conditions, without the need
for on-site calibration.
A higher level of accuracy, since the Sigma 920
automatically corrects the effects of temperature on level
measurement.
Patented `Drawdown Correction´ feature corrects
the effects of velocity on accurate level measurement.
Ideal for:
Short Term Flow Studies
Sanitary Sewer Evaluation Studies
CSO Studies and Monitoring
NPDES Stormwater Compliance
Sigma's Patented Drawdown Correction and the
Bernoulli Principle:
The Bernoulli Principle states that as the velocity of a fluid
increases, its pressure decreases. The Bernoulli Principle simply
describes the relationship between the velocity of a fluid and its
pressure. If a measurement of the pressure of the moving fluid is taken
at a point just forward of the front edge of the shape, and another
measurement is taken at the apex, of the upper curved surface, one would
notice that the pressure at the apex is lower than the pressure at the
leading edge. It is this same principle that is responsible for the lift
on an airplane wing. Level measurement using a submerged depth sensor is
similarly affected by increases in fluid velocity.
As the velocity of water increases past the
probe.
A drop in pressure (vacuum) is induced near the
pressure sensor (level) port located at the sides of the probe.
This results in the lowering of the indicated
level (or pressure) sensed at the port.
Sigma's patented "Drawdown Correction" software
adjusts the level readings for this effect. Sigma's patented
drawdown correction adjusts for these effects through software. The
software correction algorithms are based on flow data collected
during extensive laboratory and real life testing.
This testing resulted in US patent # US5691914:
Fluid flow measurement correcting system, and methods of constructing
and utilizing the same. Abstract: "An apparatus for calculating fluid
flow in a channel, comprising a probe member which detects fluid depth
in the channel; a mechanism for measuring average fluid velocity in the
channel; a mechanism for correcting the detected fluid depth based upon
the measured average fluid velocity in order to account for drawdown;
and a mechanism for calculating average flow rate based upon the average
fluid velocity measurement and the corrected fluid depth value."
*Daniel Bernoulli (1700-1782): Swiss
mathematician, son of Johann Bernoulli, who showed that as the velocity
of a fluid increases, the pressure decreases, a statement known as the
Bernoulli Principle. He won the annual prize of the French Academy ten
times for work on vibrating strings, ocean tides, and the Kinetic Theory
of gases. His Kinetic Theory proposed that the properties of a gas could
be explained by the motions of its particles. He was the first person to
encounter the functions today known as Bessel Functions.
Address:
Hach/Marsh-McBirney, 4539
Metropolitan Ct.
Frederick, Maryland
21704 USA
Telephone: U.S. and Canada 1-800-368-2723
Outside the U.S. 1-301-874-5599 - Fax: 1-301-874-8459
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