How to take only the positive section of a waveform using Labview 2009

[Edward Bajon]

I would like to take only the positive section of my waveform and discard the negative section. I would also want to calcualte the RMS value and put it in some sort of accumulator during each scan. Does any one have any ideas?

Thanks

Edward

[tbob]

Use the Get Waveform Components to get the Y array.  Wire it to a For Loop with indexing enabled.  Test each data point for >=0.  If true, pass it to a build array function.  If false, just pass the shift register contents straight through.  Rebuild the waveform using the new Y array.

For RMS, look in the palette Signal Processing - Waveform Measurements - Cycle Average and RMS

[Edward Bajon]

I will try it and see how it works.

Thanks

Edward

[Edward Bajon]

Ok, It works, but I would rather keep the time stamp the same. In other words, if you took a piece of paper and place over the negative section of the sine wave graph, then the remaining waveform is exactly what I would want to reproduce think the way it is set up right now is that it filterer the positive but compresses the data points and leaves no time in between. Is possible to use limits?

Thanks

Edward

[tbob]

Like this:

VI is attached in LV2009.

[Dennis_Knutson]

Now you are asking for something different. Instead of discarding, you want to replace all negative values with 0. The same code can be used with a minor modification in the false case.

[Edward Bajon]

This should work for my application.

Thanks

Edward

[RavensFan]

Why not put the whole array through In Range and Coerce from 0 to Inf?

[Edward Bajon]

I tested it and it works great.

Thanks

Edward

[tbob]

Smart thinking RF!