PULSAR MEASUREMENT
91
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 UltraTWIN (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
4-5 x hmax
minimum
DRWG. 7
BS3680 WEIR
