FLOW CALCULATION
The HYDRO+ provides numerous OCM flow calculation features (P600 to P611).
If the
PMD
(primary measuring device) does not match any of the 8 preset PMD
calculations, or if a PMD is not used, select a Universal Volume calculation. Use the
head/flow graph or chart provided by the PMD fabricator (or create one based on the
PMD or channel dimensions).
Based on the graph, choose the Universal Flow calculation, and select the head vs
flow breakpoints to be entered (32 max). Generally, the more breakpoints entered, the
greater the flow calculation accuracy.
Universal, Linear (P600 = 4)
This flow calculation creates a piece-wise linear approximation of the head/flow curve.
This option provides best results if the curve has sharp angles joining relatively linear
sections.
Enter a Head Breakpoint at each point where the head/flow curve bends sharply (2
minimum). For combination curves (mostly linear but include 1 or more arcs), enter
numerous breakpoints along the arc, for best flow calculation accuracy.
Universal, Curved (P600 = 5)
This calculation creates a cubic spline approximation of the head/flow curve, providing
best results if the curve is non-linear, and there are no sharp angles.
Select at least enough breakpoints from the curve to satisfy the following:
» 2 breakpoints very near the minimum head
» 1 breakpoint at the tangent points of each arc
» 1 breakpoint at each arc apex
» 2 breakpoints very near the maximum head
For combination curves, enter at least 2 breakpoints immediately before and after any
sharp angle (as well as 1 breakpoint exactly at the angle) on the curve.
flow
level
level
flow
TECHNICAL REFERENCE
PL-507 153
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