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sj250699

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01-17-2012 08:49 PM

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hi

just wondering if anyone can point me to the right direction here. Basically i just want to generate/create a series of **odd harmonics** - ranging up to the 30th harmonics - and would like to know how to do this; is it simply a matter of creating a series of sine waves multiplied by the fundamental or would i need to use such fft or psd functions of sort? Or any kind of function and to what use is the THD model? Any suggestions are welcome

thanks

JÞB

Knight of NI

01-17-2012 08:57 PM

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waveform multiplied by amplitude, dT multiplied by odd integers resample waveform- add. 30 isn't odd (nor old)

"Should be" isn't "Is" -Jay

JÞB

Knight of NI

01-17-2012 09:26 PM

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I missed the THD part.

Total Harmonic Distortion I could write an article or point you to a definition or say it is a measure of fidelity

"Should be" isn't "Is" -Jay

01-18-2012 07:24 AM

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hi there

thanks for the quick response. Not to concerned with the THD right now but ill give a good read later on.

but right now i just need to generate a series of odd harmonics to get me started. The few methods i've exercised haven't really satisfied me in a way that im sure is the right way to go. Just want to understand reading from your first post; ''waveform multiplied by amplitude'; is that something to do with fiddling around the function generator or would i have to use a few numeric functions. And dT would mean i have to use the "Get Waveform Components" function?

ill try to produce something today hopefully.and get back.

thanks very much.

JÞB

Knight of NI

01-18-2012 09:50 AM

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I'll keep an eye out for your example- Good luck!

"Should be" isn't "Is" -Jay

CoastalMaineBird

Trusted Enthusiast

01-18-2012 10:16 AM

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Fourier theorem says that any periodic signal can be broken down into a sum of sine waves, each with a given amplitude and phase, relative to the period in question.

Each sine wave can be specified as V[i] = A[i] * sin (2 * pi * F[i] * t + phase[i])), where:

A[i] is the amplitude of this component.

F[i] is the frequency of this component.

phase[i] is the phase shift of this component.

t is the time since T0.

You didn't mention phase, let's disregard that for now.

You didn't mention amplitude, lets' assume all A[i] values are 1.0

For your purposes, F[i] is going to be 1, 3, 5, 7....29 (odd harmonics below 30)

So, step thru time at your desired sample rate:

The voltage will be:

sin(2 * pi * F * t) + sin (2 * pi * 3 * F * t) + sin (2 * pi * 5 * F * t).....

you would have one loop for TIME steps, and one for harmonic steps.

Steve Bird

Culverson Software - Elegant software that is a pleasure to use.

Culverson.com

Culverson Software - Elegant software that is a pleasure to use.

Culverson.com

Blog for (mostly LabVIEW) programmers: Tips And Tricks