WOLFRAM SYSTEMMODELER TUTORIAL

Simulation CenterFFT Analysis

Introduction | Options | Experiment Browser | Plot Windows | 3D Animation | Initializing Experiments | FFT Analysis | Importing and Exporting | Keyboard Shortcuts | Input Variable Data Files | CombiTimeTable File | Simulation Settings Files | Simulation Result Files | Communication with Simulation

To do an FFT analysis, choose Tools FFT Analysis; this will bring up the FFT Analysis dialog. To select a variable for FFT analysis, switch to the Plot view of the Experiment Browser, then click and hold the right mouse button on the desired variable and drag it into the drop area in the FFT Analysis dialog. It is also possible to right-click on a variable in a plot window and choose FFT Analysis.

Options

If Remove DC component is checked, the mean value of the signal is removed before the FFT is done.

By default the FFT is performed over the time interval where the variable is defined. However, it is possible to define a custom time window by changing Time start and Time end.

Since the solver generally does not give equidistant output, the signal needs to be re-sampled. When Sampling Interval is unchecked, it will be based on the length of the time window divided by the number of output steps in that time window. The result is rounded down so that it is coherent with the next larger fast FFT size. This approach only works if the output is almost equidistant; if the model has a large amount of events that are clustered it is advisable to select a custom sampling interval.

If a custom sampling interval is entered, the number of FFT points is calculated from the chosen sampling interval and vice versa. By using a custom sampling interval and a custom number of FFT points, it is possible to do a zero-padded FFT. The resulting plot will be cut off at the selected cut-off frequency.

1.gif

FFT Analysis dialog.

Introduction | Options | Experiment Browser | Plot Windows | 3D Animation | Initializing Experiments | FFT Analysis | Importing and Exporting | Keyboard Shortcuts | Input Variable Data Files | CombiTimeTable File | Simulation Settings Files | Simulation Result Files | Communication with Simulation