Converting Peak to RMS II - The Wrath Of Dan

[@audiononsense1611]

Nice job... Science that is...

[@THELONIOUSMONstertrucK]

This is interesting, and I believe you, but I make the following points: (1) Why are we talking about this? What the original problem we're trying to address? (2) Even 80's era distortion analyzers allow the recovered distortion waveform to be fed to a spectrum analyzer, which has controls for the level detection (+/- peak, quasi-peak, and probably options for RMS as well as average) (3) The resolution (number of bins) of the FFT has huge impact on the accuracy of the measurement you take at any one frequency, analogous to the resolution bandwidth of an analog spectrum analyzer . The number of bins is finite and energy from overlapping bins leak into each other. So, trust that measurement with a grain of salt (4) Why are we doing this with function calls, and what is the piece of equipment we're controlling? I hope the response isn't a microcontroller Perhaps I just don't get the context of the discussion... there's plenty of professional, lab-grade, calibrated equipment that already does this. Why are you highlighting this one specific topic?

[@DanBullard]

This is not for a 1980s distortion analyzer, or anything as primitive as a spectrum analyzer. This is for VLSI testers that can source and capture analog waveforms using Coherent Sampling. I speak about Coherent Sampling often, perhaps you should look around my site on this topic. As to your assertion that "energy from overlapping bins leak into each other" is totally false when using Coherent Sampling. If I source and capture a wave with coherent sampling, every femtovolt of the wave I sourced goes into the bin I selected (with my M/N ratios), not one single attovolt goes into an adjacent bin. You are living in the past if you think like that. Spectrum analyzers, scopes, distortion analyzers are all garbage. Only a VLSI tester such as a Nextest Lightning, Credence VIstaVision/Duo/Quartest, Sclumberger S9000 EXA, LTX Fusion, Teradyne A5XX can do what I am talking about. Interestedly, Raytheon used a Teradyne A585 on this F16 part, and even set up the timing between the AWG (source) and ACP (capture) to be coherent, but failed to use an FFT to extract the waveform, allowing noise to become a huge part of the resulting measurement, which is why they had to take 4 million samples and average them. I got infinitely better results by taking 8192 samples 500 times fewer samples, and shaving 10 seconds off the test time. Which really doesn't matter to Raytheon, test time can be in days as far as they're concerned, they get paid by the second, so they are more than happy to waste time.

[@DanBullard]

I made a new video to address your concerns. kzbin.info/www/bejne/pn22Z5KtjdN-fbMsi=t3dBblfo69ciMrS-

[@michaelmorrison7632]

Explain "Bin" please.

[@DanBullard]

An FFT creates what is known as a Bin Histogram, from Bin 0, at the far left which stores the amplitude of any DC the waveform may have, to Bin N/2 (N being the number of samples you present to the FFT) on the right. Bin N/2 is known as the Nyquist Frequency, which is Fs/2 (Sampling Frequency) Between these two bins are (N/2)-2 bins that store the amplitude of each frequency between DC and the Nyquist Frequency. The frequency resolution of each bin is equal to Fs/N or Ft/M where Ft is the test frequency and M is the number of cycles of the test frequency acquired during sampling. I explain this often and have explained it to tens of thousands of people, both in real life and on KZbin, Matthew Mahoney wrote a book on this (DSP Based Testing) but here is my most recent video on the topic. kzbin.info/www/bejne/gYTGg3ahe7yJe5I

[@michaelmorrison7632]

@@DanBullard thanks..doing some relearning...