4230 Flow Meter
Section 2 Programming
2-7
The conversion types available are WEIR/FLUME, MANNING,
DATA POINTS, EQUATION, and FLOW METERING INSERTS.
You us e Weir/Flume flow conversion when your primary mea-
suring device is a weir or a flume. A weir is a wall or dam across
the flow stream. Water must rise to the point where it flows over
the top of the wall. The measured level upstream of the device
and the appropriate formula are used to calculate flow. Flumes
differ from weirs in that there is no wall or barrier, but instead a
restriction, typically a sharp narrowing or change in the slope of
the channel that restricts the flow.
Again, the measured level of the stream at some point ahead of
the restriction is used by the flow meter to calculate flow. In this
flow conversion mode, the flow meter uses internal look-up tables
for many common primary measuring devices.
An Equation is used when you have a non-standard primary
device, or want to use different values from those programmed
into the look-up tables of the flow meter. Equation uses the
standard flow equation:
Q = k1H
P1
+ k2H
P2
Where Q equals flow rate; k1 and k2 are constants; H is level (or
head), and P1 and P2 are the powers to which the two H terms
are raised. (Your equation may not have the second term, in
which case you would enter 0 for the second constant, k2.) Most
common primary devices are supported in the flow meter's
software, so generally you will not need this option. But it is
available for those needing to enter their own values, or for those
who have a nonstandard primary device for which an equation
can correlate level and flow.
The Manning Flow Conversion uses the Manning formula to
calculate flow in open or closed (non pressurized) gravity-flow sit-
uations based on slope, diameter, and roughness of the pipe. The
Manning formula is named for its developer, Robert Manning, a
19th-century Irish civil engineer. There is no primary measuring
device as such. Instead the pipe, with considerations for its slope
and internal roughness, serves as the primary device. The 4230
Flow Meter can calculate flow in round pipes, rectangular,
U-shaped, or trapezoidal channels based on this formula.
The Data Points Flow Conversion calculates flow based on a set
of user-entered data points for a flow stream. Data consists of
correlated level and flow measurements for the stream. Like the
Equation method of flow conversion, this flow conversion is most
commonly used where the primary measuring device is non-
standard, but where tables of level and flow rate data are
available from the device manufacturer. The 4230 has space for
four sets of data with as many as fifty points per set. The flow
meter then calculates flow from these data tables using a
three-point interpolation.
Flow Metering Insert Conversion - The inserts are installed in
upstream pipes and held with compressed air pressurizing a
bladder. They are set from street level with a handle that can be
extended as far as sixteen feet. The inserts contain a bubble line
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