OCM APPLICATION
This application is specific to monitoring the flowrate in one of the four following
categories of primary measuring devices. Refer to the respective drawings at the end
of this section for weir and flume outlines and transducer location.
Single Exponential, these are flumes and weirs that can be characterized
by a single exponential term ( P-40 = 1 ) i.e. Q = K H
X
.
where : Q = flow
K = constant
H = head
x = exponent, characteristic to the primary
measuring device (flume or weir)
Examples :
Primary measuring device
exponent
Suppressed rectangular, Cipolletti weir, or Venturi flume 1.50
Parshall Flume, or Leopold Lagco 1.55
V-notch weir 2.50
etc ......
Refer to manufacturer’s specifications for the exact exponent.
The exponents listed above are for reference only.
Palmer-Bowlus flumes : typically those manufactured by Plasti-Fab
or Warminster Fiberglass ( P-40 = 2 )
H-flumes : excluding HS and HL sizes, as developed by the U.S.
Department of Agriculture, Soil Conservation ( P-40=3 )
Other : these are primary measuring devices that do not fit the
first three categories ( P-40 = 4 )
As most OCM applications are outdoors, the use of a temperature sensor is strongly
recommended for optimum accuracy. Refer to Functional \ Temperature.
PL-443 6 – 27
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