Simeq System

Process Analysis

     XY Plot

     XYZ Plot

     Frequency Plot

     Correlation Plot

Process Control

Process Monitoring

Plant Reporting 




Example 3: Frequency Plot

SIMEQ has a command to find a frequency response of a signal.
If you in the Command Window type:

Ľ freq60('Tagname', 'From',                    'To')              e.g.

Ľ freq60('Z6MOSI',   '7-jul-03 23:20:00','8-jul-03 02:00:00')

The below plot is made based on 60 seconds samples from the log files.

The signal is first shown as a function of time. This is to check that there are no missing values or outliers
in the log files. Then a Fast Fourier Transformation is made, and finally the power spectrum is calculated and
plotted with semi logarithmic x-axes.

Frequency responses can be used to search for oscillations in signals buried in so much noise that the original
signals are not recognisable.

If 3 or 4 different frequencies plus noise make up a signal, itís very difficult to realize this without a frequency
analyse of the signal.

Another version of freq60 exists which uses 10 sec log (called freq10).


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