Xylem FC220 OPEN CHANNEL FLOW MONITOR - Manual (Page 7)

Global Water
800-876-1172
• globalw.com
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In these modes the user is either prompted to enter the pipe diameter or rectangular
channel width, in user programmable units. The WA and WP are automatically
calculated based on the diameter or width, and the measured water level.
The roughness factor is determined by the construction material, typical values are:
0.010
Plastic, other smooth surfaces
0.012 Smooth unpainted steel
0.013 Painted steel, coated cast iron
0.013 Clay drainage tile, smooth asphalt
0.013 Finished concrete
0.014 Vitrified clay sewer tile
0.014 Uncoated cast iron
0.017 Unfinished concrete
0.024 Corrugated metal storm drain
Polynomial:
A best fit 3
rd
order polynomial can also be used to calculate flow. This is useful when
you need to find an equation that best fits measured data or a lookup table. The
equation is in the form of:
Q = A + Bh + Ch² + Dh³
Where:
Q = Flow in cubic feet per second
A - D = User defined coefficients
h = Water level in feet
When selecting this mode, the user is prompted to enter the values for A, B, C and D.
Look-Up Table:
For applications where a single equation does not properly calculate flow, a single
look-up table can be programmed into the FC220. This is a factory programmable
option only. Data for this table must be provided to Global Water in two columns and
no more than 200 lines. The first column is water level in feet and the second column
is the flow in cubic feet per second at that water level. Liner interpolation is
automatically done when a measured water level is between two data points.