Example 1: XY
plot
Whenever you need to see one variable as a
function of another, you can use the SIMEQ function plotxy.
In the Command Window simply enter:
>>plotxy('x-Tagname', 'y-Tagname', 'From', 'To') e.g.
>>plotxy('Z6FreshFeed','Z6GypsumFeed','5-aug-03','15-aug-03')
If you look in the upper left corner we have
asked to have basic fitting done to the data. We have chosen a linear fit.
They show that we have been using 5.5% of gypsum as average, and that we are
working with a very small offset of 0.057.
This is perfectly Ok.
To make the basic fitting, you select the
Tools menu and then Basic Fitting. A window like the one below
will appear:
Here you can select what kind of fitting you want
to have inserted on the plot.
We have used a linear fit for this example, and
then we have chosen to have
the equation shown on the plot.
As it can be seen, many different fitting models
are included in Basic Fitting.
The list continues up to 10th
degree polynomial.
The xy plot is normally used to make a quick
check that process variables
correlate, as they should.
Another typical example is as help to find the best circulation factor for a given cement and mill. Here the xy and curve fitting capabilities are used in a programmatic way, since the raw signals needs a little treatment before they can be used for this purpose.
The above shows an optimum performance using 105 t/h rejects from a cement
mill.
The production is expected to be around 120 t/h. Circulation is then (R+F)/F
= 1.88.
In the above plot, one blue point is one minute. The red points are the LSQ
average.
See also xyz plotting.