Global Water FL16, User Manual

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V. Introduction
The FL16 Flow Monitor uses Global Water’s standard WL6 Level Logger with a
redesigned sensor housing and new software to provide a package capable of
monitoring water flow in almost any situation including partially full pipes, open
channel flumes or weirs, and even streams and rivers. The level transducer is
designed to minimize the affects of water velocity, as well as reduce fowling. The
FL16 flow software has the ability to calculate and display water flow and velocity in
partially full pipes using the Manning’s equation, has over 40 pre-stored flume and
weir equations, and can access user-defined lookup tables that correlate water level
to flow. A special feature allows you to gain maximum accuracy by adjusting
parameters to calibrate flow against empirical measurements, before or after the
data has been recorded. All of the flow parameters are stored in the logger and are
downloaded each time you connect up to the logger. These features allow any
gravity fed channel to be monitored using one easy to use product.
The Manning’s equation, first proposed in 1889 by Robert Manning, provides a way
of calculating flow and velocity in gravity fed channels of known geometry. When
applied to circular pipes, it provides accurate flow and velocity information based
only on the water level in the pipe, the pipe diameter, the slope and the construction
material. Because velocity is a product of this equation, it provides an easy way of
checking the calibration of the FL16 against actual velocity measurements, using a
velocity probe such as Global Water’s FP101 or FP201. Generally, the roughness
number corresponding to the pipe’s construction material is used to make this
adjustment and can compensate for the build-up on the inside of aging pipes. An
offset can also be applied to the measured water level to adjust for improper
installation in flumes and weirs, or allow for the thickness of the sensor itself when
deployed horizontally on the bottom of a pipe or open channel.