How average in spectral magnitude work in Spectral Measurement

[nguyenlk]

Hi everyone,

I am a Computer Science student and currently working on a project that need to transfer the work done in LabVIEW into other programming language (python). 

I was following the tutorial "LabVIEW_Spectral_Tutorial" and instead of calculating Power Spectrum I need the Magnitude Spectrum of the signal. I replicate the tutorial but added a lowpass filter and using Spectral Measurement to calculate the FFT then save the last waveform as txt file. However, in the last block, I do know the objective of the average function but I don't know how it was done in LabVIEW.

Lets say the number of averages is 5, does it mean the signal is recorded 5 trials then compute fourier transforms of each trial, get magnitude spectrum and average this across trials ? If so, how can I extract or save each result of these FFTs ? how do I know when and where the signal is recorded because It was recorded 5 times? 

I attached the VI (LV 2012 version) for your reference.

Thank you!

[GerdW]

Hi nguyenlk,

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@nguyenlk wrote:

I replicate the tutorial but added a lowpass filter and using Spectral Measurement to calculate the FFT then save the last waveform as txt file. However, in the last block, I do know the objective of the average function but I don't know how it was done in LabVIEW.

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When you convert that ExpressVI into a regular subVI (by using it's right-click menu) then you can dive into its "inner" code to explore how NI designed the averaging algorithm…

(Be aware of diving several layers of VI hierarchy!)