Difference between revisions of "User note: FFT averaging"

NVGate provides many settings for averaging result. This document aim at describing these functions and parameters for averaging data result. This document focuses on averaging available at FFT modules. These are quite similar setting for SOA modules.

There are many reasons that lead to average measurement to get accurate results.

Averaging parameters should be setup according analysis and tracked phenomena.

Averaging could be done in either '''Frequency''' or '''Time Domain'''.

Each signal block generates an FFT, the average result is the average of the spectrum :

Data result is available for magnitude only. There is no information about the phase.

The average is performed in time domain, the FFT is computed on the average time signal data

This allows to focus on a specific phenomena even if there is no trigger available to perform Time domain analysis.

For the '''linear average''', each "n" spectrum get the same weight for the averaging. It usually set for long time averaging result. The result is according the global level of energy for each narrow band during the duration of measurement.

[[Image:Averaging_05.png|framed|none]]

The '''Exponential Average''' is computed with a linear average for the last "n" spectrums whereas older spectrum has a lower weight. Exponential average provides an infinite sliding result. This is commonly use with a low value of average. As it kept the student variation in memory for a short time, this is a good setting for monitoring or tracking non temporary phenomena.

[[Image:Averaging_06.png|framed|none]]

The '''Peak Hold average''' is not any mathematical average. The peak hold provides a result that correspond, at each band, for the maximal value of each the "n" spectrum. It is useful to get the maximal values as a worst case of measurement:

[[Image:Averaging_07.png|framed|none]]

In the same way the '''Ref. Peak Hold average''' is no more a mathematical average.