Building of Frequency Spectrum from Oscillogram Signal

For the program for oscillogram viewing in COMTRADE format, the functionality of constructing the frequency spectrum for an arbitrary analog signal from the waveform is added.

A new button has been added to the toolbar. When you click on this button, the waveform is hidden, and the screen displays a form for selecting an analog signal for which it is necessary to construct a frequency spectrum (Fig. 1). The remaining buttons, except for the graph scaling buttons, become inactive. When you press the button again, the screen for constructing the spectrum of the analog signal is hidden, and the waveform is displayed in the form in which it was before pressing this button.


Fig. 1. The program interface for constructing the frequency spectrum of an analog signal

To build the frequency spectrum, it is necessary to select a signal from the list generated automatically by the program from the CFG file and specify the signal interval from the waveform for which it is necessary to construct the spectrum. By default, the program sets the range from the beginning to the end of the waveform. The sample rate of the signal will be determined automatically. To start the calculation, click the “Calculate” button.

2 graphs will be displayed on the screen (Fig. 2). The signal in question will be displayed on the upper graph. The lower graph will display the amplitude spectrum of the signal in question. The spectrum is built up to the Nyquist frequency equal to half the sampling frequency of the observed signal.


Fig. 2. The signal under consideration and the amplitude spectrum obtained

If it is necessary to expand or narrow the interval of the signal under consideration, set the required interval and press the “Calculate” button again (Fig. 7). The frequency spectrum of the signal will be rebuilt.

More detailed instructions for using the oscillogram viewer can be found here.

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