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Need help with microsoft excel

  1. Nov 6, 2013 #1
    Hello.
    I have this set of data that I have to plot with excel but I only need to plot for ONE PERIOD of the waveform. But how do I determine from what data to what data is one period? In the data, the left side is time (s) and right side is the voltage (V).
     

    Attached Files:

  2. jcsd
  3. Nov 6, 2013 #2

    UltrafastPED

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    Look at the data; find the minimum value - then follow the data up to its next local maximum, then back down its next local minimum.

    That is one period - the cycle has returned to its starting point. Note that you won't find the _exact_ same value for the two minima; for that you would need perfect data, which does not exist.
     
  4. Nov 6, 2013 #3
    The first data is a positive but the second date is a negative. How is that? Should I start from the second or first data if I wanted to start from 0 sec?
     
  5. Nov 6, 2013 #4

    UltrafastPED

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    Or you can start at the first zero, go up, then down, cross a second zero, go negative to the lowest point, then back up to the crossing point ... that is one complete period.

    You can actually start a period anywhere ... you just need to get the complete cycle. For your data this will include both the positive and the negative part.

    But it is easiest to go from max to max, or min to min ... then you don't need to study the data so carefully. Note that starting at zero as above you only have a half cycle if you stop at the second zero.

    This tutorial has clear pictures: http://www.physicsclassroom.com/Class/waves/u10l2a.cfm
     
  6. Nov 6, 2013 #5

    mfb

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    That does not work, the data is not a nice sine curve.

    Graph all of your data, then the approximate length of a period should be obvious.
     
  7. Nov 6, 2013 #6
    the result is indeed not a nice sine data and my task is supposed to find out the reason, but first I have to graph this for one period.
     
  8. Nov 6, 2013 #7
    This is what I got. I start from 3.13E-01 and then to -3.13E-01 and then back to 3.13E-01. Is this right?
     

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  9. Nov 6, 2013 #8

    mfb

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    Can you plot the whole data range as comparison?
     
  10. Nov 6, 2013 #9

    UltrafastPED

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    I skipped all of the headers .... imported starting at row 10, which is the data.

    Then plotted columns A,B ... changed axes to be column A, which was removed from the plot.

    Here is the pdf ... you can see the repetitions: a bunch of digital data positive, then negative ... then it looks like it repeats. One up block, one down block.

    You could verify if this is a repetition by generating a new graph which is the _difference_ between the first period and the second period. Scale them. If not a good match, try including another pair of blocks.
     
    Last edited: Nov 10, 2013
  11. Nov 6, 2013 #10
    What you plotted is not one period, but the whole time, isn't it?
     
  12. Nov 6, 2013 #11

    berkeman

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    Yes, he plotted all of the data. Your plot in post #7 looks correct for one period.
     
  13. Nov 6, 2013 #12
    Could you teach me how to change the values into their normal form? I mean, I want to get rid of the 'E'.
     
  14. Nov 6, 2013 #13

    UltrafastPED

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    Right click on the axis to be modified, select Number ... and change the settings to what you like.

    Or just click on the data column and change the formatting for the column; be sure to include enough decimal places.
     
  15. Nov 6, 2013 #14

    berkeman

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    In Excel, click on the top of the column you want to format, in order to select the whole column.

    Right-click the highlighted column's top, and select "Format Cells".

    On the Number tab, choose the number formatting that you want, and click OK.

    :smile:


    EDIT -- Beat out by Ultrafast! (hence the name...)
     
  16. Nov 6, 2013 #15

    UltrafastPED

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    The moniker actually stands for "Ultrafast Photo-Electron Diffractometer" which measures laser-matter interactions with sub-picosecond temporal resolution. Ultrafast lasers generate pulses that are measured in femtoseconds ...
     
  17. Nov 6, 2013 #16
    Is this correct? I am not sure about the time, though. How is it 300 something seconds? I replotted for one period and there is a slight change compared to the one I posted before. I don't get it, which one is correct?
     

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  18. Nov 6, 2013 #17

    UltrafastPED

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    You have to change the axis data: the default is to just use a counter. You need to select the first column data as the axis.

    And delete the time data from the plot; it should be channel 1.
     
  19. Nov 6, 2013 #18
    Can you do it for me? I don't get what you mean.
     
  20. Nov 6, 2013 #19

    UltrafastPED

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    Use the help button, and enter "axis formatting". The instructions vary with the version of Excel.
     
  21. Nov 6, 2013 #20

    berkeman

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    In Excel, click the Help icon, and type Format Axes into the search box. The first hit on the list of topics should be what you need.

    EDIT -- I don't believe it! Beaten out again!
     
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