circular waveform using oscilloscope

Discussion in 'Homework Help' started by Rubs, Jun 27, 2011.

  1. Rubs

    Thread Starter New Member

    Jun 20, 2011
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    how can i generate a circular waveform on an oscilloscope using function generator?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    Rubs likes this.
  3. Rubs

    Thread Starter New Member

    Jun 20, 2011
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  4. Georacer

    Moderator

    Nov 25, 2009
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    There is no rectangular shape possible with this method. Lissajous curves come in the pattern shown in the red images in the Wiki link beenthere gave you.
     
  5. Rubs

    Thread Starter New Member

    Jun 20, 2011
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    u mean we cannot generate a parallelogram using a function generator?:confused:
     
  6. Georacer

    Moderator

    Nov 25, 2009
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    A function generator can only give you, as it says, a function. That means that if you draw a vertical line anywhere in the graph, it will intercept the signal only at one point. A parallelogram will be intercepted at two and thus isn't a valid time signal.

    Do you by any chance mean a square wave?
    http://en.wikipedia.org/wiki/Square_wave
     
  7. Rubs

    Thread Starter New Member

    Jun 20, 2011
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    yea i knw dat...even a circle is generated using two sine signals with a phase difference of 90 degree. so my question remains..how to generate a parallelogram?
     
  8. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Try to reconstruct the signals needed to make a paralleogram.
    It will be something like a trapezium like signal on one side.

    Bertus
     
  9. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    To draw a straight line one side is held steady while the other ramps from one voltage to the other. To draw a diagonal line both sides would ramp from one voltage to the other.

    This was once done on computers and was called a "vector display." However, that term has been usurped by the latter day PC crowd so a search will generate many false hits.

    To do it properly you might try a pair (or 2 channel?) of arbitrary waveform generators, but that widget ain't cheap. To do it on the cheap you might want to try the sound card audio output on your PC: left & right become X & Y.
     
  10. BillB3857

    Senior Member

    Feb 28, 2009
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    Two triangle waves, 90 degrees out of phase tied to X and Y inputs on scope?
     
  11. Georacer

    Moderator

    Nov 25, 2009
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    If X and Y are the two input signals, starting from 0, a square with a side of 1 could be drawn parametrically like this:

    For t=(0,t1) X=0, Y=t/t1
    For t=(t1,t2) X=(t2-t)/(t2-t1), Y=1
    and so on...

    That requires an arbitrary signal generator as Ernie said. Why don't you try it in a simulation software for starters?

    Is that clear?
     
  12. #12

    Expert

    Nov 30, 2010
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    I can just about see it with a triangle wave on the x input and a clipped triangle wave on the y input. A resistor to a pair of diodes to do the clipping for the y input.

    Function generators don't provide clipped triangles. That forces the use of hardware to do it this way.
     
  13. someonesdad

    Senior Member

    Jul 7, 2009
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    If you use the X and Y inputs of the scope (e.g., for Lissajous figures) and the Z input, then you can draw anything that you can draw on a piece of paper with a pen. I haven't seen a Z input on a scope in a couple of decades though... :p Theoretically, you can also do it without the Z input; it's just harder.
     
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