# LabVIEW

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## Odd Harmonics

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

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## Re: Odd Harmonics

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

"Should be" isn't "Is" -Jay
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## Re: Odd Harmonics

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
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## Re: Odd Harmonics

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.

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## Re: Odd Harmonics

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

"Should be" isn't "Is" -Jay
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## Re: Odd Harmonics

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

Blog for (mostly LabVIEW) programmers: Tips And Tricks

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