Data AcQuisition And Real-Time Analysis
Scope - Spectrum - Spectrogram - Signal Generator
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Spectrum Analyzer

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THD Meter

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Spectrum Averager Peak Mode

Controls: Spect Avg Dialog >> Peak
Macro: SpavgMode=Peak

This isn't really an "averager" mode at all. In this mode, the peak value is retained at each frequency, for as many frames as you have specified. Typically, you would set this value very high and terminate the operation manually by hitting the Pause button.

You can specify Continuous Peak mode by setting the frames request to 1. (A single frame wouldn't otherwise be useful.) In this mode the total frames display will continue to increase until it reaches 2147483647, after which it will show 'Cont Peak' instead of a number. Peak operation will continue until you hit Pause, or toggle Average off to abandon it.

A typical use for Peak mode is to generate a swept frequency response that appears on a single trace. You set a very slow frequency sweep to drive the system under test, and the Peak mode will record the maximum amplitude at each frequency. See Swept Frequency Response for details.

You should typically use a Flat Top spectral window function for this application, to insure accurate peak amplitude capture.

Peak mode is also ideal for looking at explosions, animal calls, music recordings, or anything else where you might want to know about spectral peaks but the source is not well-behaved or repeatable enough to use with a normal sync.

One such use is in determining vehicle pass-by noise, which is how much noise a vehicle makes as it passes by at a fixed distance. You just start the "average", wait for the vehicle to pass, and then hit Pause to see the result. You don't usually need to worry about precise timing because the vehicle will be much louder than anything else at most frequencies, so the peak will only reflect that one source.

Note that you can obtain a single dB value in addition to the spectrum. You can specify a selected portion of the spectrum with the solid and dotted cursors, and use the Sigma readout mode to get the included energy between them. You can use the Spectrum Curves dialog to apply a Weighting Curve, either a standard curve such as A or ITU-R 468, or a custom curve that you define.

Alternatively, you can use the Peak Hold option of the Sound Level Meter to get a reading of the overall spectrum, with or without the same Weighting Curves.

Macro Notes:

SpavgMode=Peak or SpavgMode=2 sets Peak mode. See Macro Notes under Spectrum Averager Mode for the complete list of mode numbers and names.

See also Averager and Spectrum Averager Controls.


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