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I have a bunch of readings of a wave consisting of volts and time. I need to calculate the frequency of the biggest wave, but i'm not sure exactly how. From what I've researched I'm thinking I need to find the largest reading (volts) and that would be my biggest wave. Then I need to search for the closes value to zero before the peak and then the closes value to zero after the corresponding troth. Measure the time it between those two values and then 1/time.

Am i correct and is there an easier way ?

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    $\begingroup$ Did you consider using Fourier transforms? $\endgroup$
    – Bernhard
    Commented Jun 30, 2013 at 9:26
  • $\begingroup$ I don't know what that is ... just saw it on wikipedia but I can't understand the formulas ( i don't know physics other than what i learned and have now forgotten from high school). To clarify on the above the readings consist of a (time) (volts) table. $\endgroup$
    – ZeW
    Commented Jun 30, 2013 at 9:36
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    $\begingroup$ I would start by drawing a graph of voltage against time and see if anything obvious catches your eye. $\endgroup$
    – John Rennie
    Commented Jun 30, 2013 at 10:23

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If all you have is the data, just measure the time difference between where a waveform starts and where it repeats. This is the period (T) of the wave. Frequency is then easily calculated by $f=\frac{1}{T}$.

For example a sine wave shown in this image (sorry I can't post images yet)

T=0.6-0.18 = 0.42 s

F=1/.42 = 2.38 Hz

For more complex waveforms you have to be careful what you are really getting the frequency of. You can find where the complex wave is periodic, however it will not tell you the frequency components of this waveform. This is where a fourier transform will help by showing you the spectral contents. The most common way to do this is to run your data through an FFT (fast fourier transform). Try this on-line FFT tool if your data samples are at regular intervals then it should work for you.

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  • $\begingroup$ Thank you that's what I thought ... however I've ran into a problem ... I actually have to write a program that finds the frequency ... of the maximum amplitude wave in a table with readings. Problem I've ran into is how to find the frequency for waves like these: s21.postimg.org/i9hmbhj07/Untitled.png s21.postimg.org/e1mu2qhkn/Untitled_1.png $\endgroup$
    – ZeW
    Commented Jul 6, 2013 at 0:00
  • $\begingroup$ FFT will tell you this, since it will return a frequency-amplitude curve. So you can just look at the highest amplitude. I would expect that there are FFT tools for the code you are using to write your program. $\endgroup$
    – fibonatic
    Commented Nov 28, 2013 at 14:25
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If you're taking reading from an oscilloscope then, yes you will find the largest wave peak to peak. Most oscilloscopes often have a setting where you can measure the peak to peak voltage (which is in the y-axis). From that point you'll most likely need to measure the distance between each trough and then 1/t will give you the frequency of that given trough. You can also measure over the total amount of troughs that are on the oscilloscope screen then just divide the total amount of time by the amount of periods then 1/t.

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