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February 17th, 2015, 10:50 AM  #1 
Newbie Joined: Feb 2015 From: KY Posts: 1 Thanks: 0  Harmonic Calculation from Data Points
I should start by saying I haven't taken a calculus class in about fifteen years so anything you can phrase in layman's terms would be helpful. I have watched and read quite a bit on this subject online, but it seems every time they get to the calculations there is some assumed knowledge of symbols I either don't remember or never knew. I am trying to take measurements from a cylindrical object and extract its harmonics from the rounded edge as it spins. I have a spreadsheet which is supposed to have done that by using the Root Mean Square averaging of the wave (cell D133 of link). However, I need to cut the root mean square step, and provide the actual harmonic values at each point. I don't really understand how this first harmonic was calculated well enough to make this happen. I do however understand the changes to the angles needed to calculate the later harmonics. Here are the assumptions I am working with so far The average value is how much my collected data point deviates from the expected norm. The angle was calculated by taking 128 equidistant points across the 360 degrees of the object. The wave hits a peak point twice to complete one period, so the peak to peak can also be found by hitting the average X value twice. Slightly fuzzy I thought the X and Y values are the traditional Cartesian coordinates of the first harmonic expressing the information in circular complex form. I am not so certain of this as some of the values don't make perfect sense. I am not super confident on the math used for these though I understand basic SIN and COS. The angle of the harmonic was determined by atan2 and letting the spreadsheet convert to degrees. I could use a little exposition here of what this really means other than it can be used in the formula to calculate the actual harmonic points in column F. Main Problem How do I calculate the harmonic values without using RMS? If you can clarify any of this, I would very much appreciate it. If you would like to write directly on the reference spread sheet, feel free. Thanks Last edited by Czern; February 17th, 2015 at 10:54 AM. 

Tags 
calculation, data, data points, fourier transform, harmonic, points 
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