Epson CMD-2260 (CD-ROM) Technické informace stáhnout pdf (Strana 223)

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Blastware Advanced Module

Blastware Operator Manual 6–33

Choose a waveform to remove the offset in the first drop–down menu. In the second drop−down

menu, choose a waveform window to display the new waveform. Lastly, name the new waveform.

Press OK to create the new waveform. If you would like to remove the offset from all of the

channels, click on the All Channels button.

6.9.12 FFT Analysis

The FFT Analysis command selects a portion of a waveform to perform an FFT calculation upon,

or if desired, the complete waveform. For a partial FFT Analysis, select a waveform section by

either specifying the time or the sample number. Select start and end points at zero crossings to

reduce the high frequency component that may be introduced by truncating the waveform. When

the FFT dialog box appears, the default start and end time correspond to the present cursor

positions.

To perform an FFT, open the Process Menu and select the FFT Analysis command. For a Partial

Waveform FFT Analysis, click on the second radio button (as shown below), and enter a Start and

End time, or a sample number. You do not have to enter both. Click OK. The FFT appears within

the Analysis Window. For a full analysis, click on the FFT Analysis on Entire Waveform radio

button.

Note: FFT calculations may require a period of time to complete. The time required depends upon

the size of the waveform and the speed of the computer.

a. FFT Analysis Limitations - Description

In simple waveforms, not composed of many different frequencies, the dominant frequency may

be at the peak particle velocity of the waveform. In more complex waveforms, the dominant

frequency is not necessarily the frequency at the peak particle velocity but at the frequency with

the greatest amplitude. Whether or not this frequency actually contributed to the peak particle

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Epson CMD-2260 (CD-ROM) Technické informace Strana 223