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Oscilloscope calculations

  1. Oct 30, 2016 #1
    1. The problem statement, all variables and given/known data
    V1 = 10cos(10^4t)
    V2 = 5cos(10^4t + pi/3)
    Time Base setting = 0.1msec/div

    By how many divisions will these two traces differ?
    2. Relevant equations
    W = 2pi/T


    3. The attempt at a solution
    W = 2pi/T
    T = 2pi/W
    W = 10^4
    T = 0.628 milliseconds
    0.628milliseconds/(0.1msec/div) = 6.28 divisions
    Would the difference between 10cos and 5cos add a factor of 2 or 1/2 to the # of divisions?
     
  2. jcsd
  3. Oct 31, 2016 #2

    CWatters

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    No. The 10 and 5 give you the amplitude. For example at a peak, when cos(...) =1, one waveform has the value 10 and the other 5.

    Hints:

    a) Both waveforms have a common 104t term. What does that mean?
    b) One also has another term pi/3. What does that represent?
     
  4. Oct 31, 2016 #3

    NascentOxygen

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    You are making this difficult for yourself if you are attempting to answer this question without first sketching how the oscilloscope is displaying these two signals.

    If you think you don't need to sketch this, then I say you most certainly do need to‼‼
     
  5. Oct 31, 2016 #4
    a. Same frequency
    b. Phase shift
     
  6. Oct 31, 2016 #5

    CWatters

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    Correct.

    Which of a and b shifts the trace left to right along the time axis relative to the other?
     
  7. Oct 31, 2016 #6
    B would shift the graph over to the right by pi/3?
     
  8. Oct 31, 2016 #7

    CWatters

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    Correct.

    Although I think V2 would be shifted left relative to V1.
     
  9. Oct 31, 2016 #8
    So how many divisions will these two traces differ?

    Pi/3 divisions?
     
  10. Oct 31, 2016 #9

    gneill

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    You have calculated the period of the signals (the time for one cycle). How much of one period does the phase angle represent? What is it in milliseconds?
     
  11. Oct 31, 2016 #10
    1/3 of the period?
    0.209 ms?
     
  12. Nov 1, 2016 #11

    gneill

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    Can you show how you determined the 1/3 value? Is pi/3 really 1/3 of a full circle?
     
  13. Nov 1, 2016 #12
    Pi/3 is 1/6 of the total period, so would it be 0.105ms or 1.05 divisions?
     
  14. Nov 1, 2016 #13

    gneill

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    Staff: Mentor

    That looks better!
     
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