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

Controls: Spect Avg Dialog >> Exponential
Macro: SpavgMode=Exp

This mode provides a continuously averaged spectrum, without the need for repeated starting and stopping, when you want to monitor an experiment. For example, by reducing the jitter in the noise floor you can get a better view of its average value, which may be an important indicator of the relative condition of the system under test.

Exponential averaging provides a continuous average which looks like the normal Linear spectrum averager output, only it is always "live". It is a weighted average of multiple frames, with more recent data having more influence on the result, and very old data being effectively ignored. In this way, you can get a better view of the desired signal, at a cost of slow response to a sudden change.

Exponential averaging is identical to Linear averaging until the requested frames value is reached. After that the averager continues to operate in exponential mode, with the requested frames value acting like a time constant. Larger time constants cause the average to react more slowly to changes in the signal, since there are more old frames contributing to the total.

A running exponential average will show the total number of frames accumulated in the Total Frames Counter (beneath the Averager button). When the total reaches the requested time constant, the value will stop increasing. It will be cleared when the average is abandoned by toggling the Averager off.

Macro Notes:

SpavgMode=Exp or SpavgMode=1 sets Exponential mode. See Macro Notes under Spectrum Averager Mode for the complete list of mode numbers and names.

See also Averager, Spectrum Averager Controls, and Linear Spectrum Average, Spectrum Averager Theory


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