Algorithm for Counting AC Events

[ASTDan]

Hello,

 

I am trying to develop an algorithm that counts the amplitude of AC "events" (see attached screen shot)

 

 

In the graph there are 3 events.  Does anybody have any idea on how to detect this?

 

Thanks

 

Dan

[crossrulz]

cross posted on the dark side: http://forums.ni.com/t5/LabVIEW/Algorithim-on-AC-waveform/m-p/2537348#M769268

[Jordan Kuehn]

Here is one simple implementation using a Hilbert Transform and taking a derivative of the envelope. Here's some reading that covers way more about this transform than matters for this discussion, but has a nice picture at the bottom of page 8.

Something similar could be done with the ptbypt RMS suggestion you have on your dark side thread.. Take what you want from it.

[ShaunR]

Use the AC & DC Estimator VI to measure Vrms and just note when Vrms changes.

[Jordan Kuehn]

Use the AC & DC Estimator VI to measure Vrms and just note when Vrms changes.

 

If you went this route you could replace the hilbert function with this implementation in what I sent you and still capture the transitions in a similar fashion.  Lots of options.

[GregSands]

This Hilbert code doesn't cope well with changing the amplitudes (try 3, 7, 10), nor with a different first and last amplitude.  

[Jordan Kuehn]

Try adjusting the thresholds on the peak detection..  I debated including a graph of the derivative or not. It will behave differently than the RMS, and I'm not even suggesting it is the best option, but it can be useful.

[ShaunR]

If you went this route you could replace the hilbert function with this implementation in what I sent you and still capture the transitions in a similar fashion.  Lots of options.

 

I wouldn't. I'd just take rate of change (dy/dx) of the Vrms and if it went outside a value, count the event (assuming it's a bit noisy and not zero when unchanging).

[Jordan Kuehn]

That's essentially the same thing?

[ASTDan]

I tried using a high pass filter and achieved some interesting results.  I will be using real data soon, I will let everyone know the results I get.

 

Thanks