Getting Started with Your 2700 Series Instrument

The FFT Spectrum Analyzer Chapter 5: Quick Guides
Transformation. The windowed audio data is transformed by the FFT.
This results in an array of points describing the magnitude and phase of
each frequency in the audio signal.
Display. The control software fetches the transformed audio data and
graphs it. Because the number of transformed points is typically larger
than the number of points in the graph, a peak-picking method is used to
ensure that peaks in the frequency data are not missed.
For more information, see Appendix C of the 2700 Series User’s Manual.
Setting up an FFT
Click New Test and open the Digital Analyzer panel. After a New Test, the
Digital Analyzer panel defaults to None as its analyzer. To switch to the Spectrum
Analyzer, click the down arrow next to the Analyzer field at the top of
the Digital Analyzer panel. From the list, choose FFT spectrum analyzer
(fft). The panel changes to display the analysis tool.
Panel Fields
There are two peak monitors near the top of the panel, one for each of the
stereo channels. These meters give an indication of the presence of signal at
the FFT input.
Below the peak meters is an array of fields for configuring the analyzer.
Here, we will use the default settings. For more details on the settings, see
Chapter 11 of the 2700 Series User’s Manual.
Time vs. Frequency
Figure 28. FFT Spectrum Analyzer panel.
As mentioned, the FFT spectrum analyzer can display audio signals in the
time domain and the frequency domain. The choice of domain is determined
by the Source 1 field on the Sweep panel. If it is set to Fft.FFT Time, a time
Getting Started with Your 2700 Series Instrument 47