56
BE 57-660 Eclipse Model 700 Guided Wave Radar Transmitter
3
.4.5.2 Configuration using Generic Equation
The following table provides an explanation of each of the
System Configuration parameters for Open channel flow
applications using the Generic Equation.
Configuration Parameter Explanation (Open Channel Flow — using the Generic Equation)
Flow Units
A selection of Gallons/Minute (factory default Flow Unit), Gallons/Hour,
Mil Gallons/Day, Liters/Second, Liters/Minute, Liters/Hour, Cubic Meter/Hour,
Cubic Ft/Second, Cubic Ft/Minute, and Cubic Ft/Hour are provided.
Flow Element
S
elect one of the following primary Flow Elements that are stored in the firmware:
Parshall flume sizes of 1", 2", 3", 6", 9", 12", 18", 24", 36", 48", 60", 72", 96",
120" and 144". Palmer-Bwls (Palmer-Bowlus) flume sizes of 4", 6", 8", 10", 12",
15", 18", 21", 24", 27" and 30". V-notch weir sizes of 22.5
O
, 30
O
, 45
O
, 60
O
, 90
O
and
120
O
. Rect with Ends (Rectangular Weir with End Contractions), Rect w/o Ends
(Rectangular Weir without End Contractions), and Cipoletti weir. Custom Table (see
page 57 can be selected if none of the stored Flow Elements can be used. The
table can be built with a maximum of 30 points. The Model 700 also has the capa-
bility of using a Generic Equation (below) for flow calculation.
Generic Eqn Factors
Generic Equation is a discharge flow equation in the form of Q = K(L-CH)H
n
, where
Q = flow (Cu Ft/Second), H = Head (Feet), K = a constant, and L, C and n are user
input factors that depend on which Flow Element is being used. Make sure the flow
equation is in the form of Q = K(L-CH)H
n
, and proceed to enter the values of K,L,C,H
and n. See example below.
NOTE: The Generic Equation parameters must be entered in Cu Ft/Second
units. The resultant flow is converted by the Model 700 into whatever Flow Units
are selected above. See example below.
Reference Dist
The Reference Distance is measured from the sensor reference point to the point
of zero flow in the weir or flume. This must be measured very accurately in the
user-selected level units.
Maximum Head
Maximum Head is the highest liquid level (Head) value in the flume or weir before
the flow equation is no longer valid. The Maximum Head is expressed in the user-
selected level units. The Model 700 will default to the largest Maximum Head value
that is allowed for any given flume or weir. The Maximum Head value can be revised
depending on the value of the Reference Distance, or for end user preference.
Maximum Flow
Maximum Flow is a read-only value that represents the flow value corresponding
to the Maximum Head value for the flume or weir.
Low Flow Cutoff
The Low Flow Cutoff (in user-selected level units) will force the calculated flow
value to zero whenever the Head is below this point. This parameter will have a
default and minimum value of zero.
Using the factors above the equation becomes:
Q = 3.33 (8-0.2H) H
1.5
The discharge flow value for a Head value of three feet
becomes 128.04 Cubic Ft/Second. If GPM was selected for
the Flow Units, the Model 700 Measured Values screen would
display this value converted to 57,490 GPM.
Generic Equation Example (using equation for an 8' rectangular weir w/ end contractions)
Q = Cubic Ft/Second flow rate L = 8' (weir crest length in feet) H = Head value
K = 3.33 for Cubic Ft/Second units C = 0.2 (constant) n = 1.5 as an exponent
Q = K(L-CH)H
n
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