ULTRA 4 INSTRUCTION MANUAL
94
BS3680 Weirs (P700 = 3)
Point of Measurement
The transducer must be above the maximum head P704 by at least the
near blanking distance P107.
For a Rectangular and V-notch weir, the head is measured at a point 4 to 5
times the maximum head upstream from the weir plate, to ensure the
surface of the liquid is not affected by turbulence or drawdown. (See DRWG
7)
Rectangular Weir Calculations
Absolute
If the flow calculation is to be absolute P702 = 1 the flow will be calculated
using the formula: q = C
e
2/3(2gn)
0.5
b
e
h
e
1.5
Where:
q = flowrate
Ce = discharge coefficient calculated by Ultra 4 (P723)
gn = gravitational acceleration (nominal value = 980.66 cm/s
2
)
be =effective approach width where b is approach width (Dim “A”) P710
he = effective head
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