Oscilloscope in xy mode

Discussion in 'General Electronics Chat' started by boredaxel, Mar 19, 2012.

  1. boredaxel

    Thread Starter New Member

    Feb 15, 2010
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    Hi, I am wondering if I put the oscilloscope in xy mode with inputs coming from 2 ac voltage source. Since the display is not time varying now, will the 2 voltage source be displayed as their rms value instead?
     
  2. Audioguru

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    Dec 20, 2007
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    An oscilloscope shows peak-to-peak voltage levels.
    Try feeding a stereo signal to the vertical (left channel) and horizontal (right channel).
    Do not leave the scope with a bright dot when the music is not playing because the screen will be burnt.
     
  3. boredaxel

    Thread Starter New Member

    Feb 15, 2010
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    Hi Audioguru, so does this mean that instead of a time-varying waveform, because now the x-axis is another input voltage source, the x-axis will be the peak to peak of that input voltage source. And the same for the y-axis?
     
  4. Audioguru

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    Dec 20, 2007
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    Correct. A stereo signal will look like a tangle of string always moving.
    Mono will be a straight diagonal line.
     
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  5. crutschow

    Expert

    Mar 14, 2008
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    If you put in a sinewave of the same frequency with a phase-shift between X & Y you will get an oval display. A 90 degree phase-shift will give a circle (if both amplitudes are the same)
     
  6. atferrari

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    Jules worked on that a lot.

    Google for Lissajous
     
  7. bertus

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  8. MrChips

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    If you put stereo audio signals into the x and y channels you will observe the differences between the left and right channels, i.e., how much stereophonic information is present.

    If there is little difference (such as mono), you will see a diagonal line.
     
  9. Audioguru

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    Years ago I built a SQ full-logic surround sound decoder using Motorola ICs. It used stereo vinyl records (remember them?) but with SQ surround sound encoded with phase shifts. The phase shifts in the decoder made weird displays on my XY 'scope when playing ordinary stereo through the decoder.
     
  10. MrChips

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    Years ago I acquired a 9-inch video monitor that someone modified into an XYZ scope.
    I had built a quadraphonic audio system (similar to your SQ surround sound system) and used the XYZ scope to display the stereo channels. It was neat watching the display patterns generated by the music. The Z (intensity) was modulated by the volume level of the music.
     
  11. atferrari

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    Do you remember the max/min voltages you used for that?
     
  12. MrChips

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    No, I don't remember. But the circuitry was completely redesigned with a lot of op amps in order to accept typical audio line levels, which I guess is about 600mV? Besides there was a LEVEL pot. The beam spot was fully bright on loud music and dimmed to totally dark as the music faded. It was important not to leave a dot on the center of the screen when the music ended.
     
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