Pulsar ULTRA 5, Instruction Manual, Page: 127 / 258

Page
119
BS3680 Thin Plate Weirs
Point of Measurement
The transducer must be above the maximum head P704 by at least the near
blanking distance P107 .
For Rectangular and V-notch weirs, 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 8
)
Calculations
BS 3680 Rectangular Weir
A
BSOLUTE
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 the Flow 5 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