Oscilloscope in xy mode

Thread Starter

boredaxel

Joined Feb 15, 2010
2
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?
 

Audioguru

Joined Dec 20, 2007
11,249
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.
 

Thread Starter

boredaxel

Joined Feb 15, 2010
2
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?
 

Audioguru

Joined Dec 20, 2007
11,249
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?
Correct. A stereo signal will look like a tangle of string always moving.
Mono will be a straight diagonal line.
 

crutschow

Joined Mar 14, 2008
26,407
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)
 

MrChips

Joined Oct 2, 2009
22,893
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.
 

Audioguru

Joined Dec 20, 2007
11,249
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.
 

MrChips

Joined Oct 2, 2009
22,893
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.
 

MrChips

Joined Oct 2, 2009
22,893
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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