Operating Manual

Accu-Wave Chapter 3 Set up Level, Level Alarms, and Volume
TN Technologies 3-17
Up to eight segments can be defined to describe the tank shape. After you set up segment
#1, the menu will prompt you to “Assign & setup segment #2,” and so on. If you do not
need to specify another segment, simply scroll past the “Assign & setup segment” menu
item.
For each segment, you select a segment type (shape), specify the corresponding
dimensions, the starting level (level at the bottom of the segment), and the ending level
(level at the top of the segment). Two or more segments can be assigned the same type
(shape). In addition, the segments may overlap, that is, the top and bottom of one segment
may be located between the top and bottom of any other segment. This can be useful in
setting up compound shapes, for example, a vertical cylinder with a rectangular
appendage. Another example is two vertical cylinders that are connected so the level is the
same in both. The Accu-Wave gauge can be set up to measure the level in one cylinder,
but to compute the combined volume of both cylinders.
Once you have set up the tank segments, you can later modify the parameters for any of
the segments you have defined, changing the segment type (shape), dimensions, starting
level, or ending level of any of the segments.
Polynomial Expression for Volume
In addition to the pre-defined shapes in the above table, you can define the volume in a
segment using a sixth order polynomial expression of the height (level) in the segment. The
following formula is used to calculate the volume, V, in the segment:
V = A H + B H
2
+ C H
3
+ D H
4
+ E H
5
+ F H
6
,
where:
H = height of material in the segment, and
A, B,…,F = polynomial coefficients (may be positive or negative).
When the “type 20, Vol = polynomial of height in seg” option is selected for the segment
type, the user is prompted to enter values for the six polynomial coefficients, A through F.
No constant term (zero order coefficient) is included in the polynomial expression for
volume. However, the “volume in tank when level reading is zero” menu item allows you
to specify a non-zero volume at the “zero level” point.
The value computed by the polynomial expression depends on the volume and height units
specified by the user. You must select the coefficients to give the proper value for volume
as a function of the height (level) in the segment for the specified units. For many
applications, a second order expression (specify A and B coefficients and leave other
coefficients set to zero) provides sufficient accuracy.
Volume Break Table (1
st
or 2
nd
Order)
The final option for specifying the volume in a segment is to define a volume break point
table. A volume break point table contains up to 16 volume/height data pairs which define
the tank volume as a function of height within the segment.