X-Y Plot

X-Y Plot (Lissajous)

This display export shows the X-Y plot of two sinusoids of frequency ratio almost 1:3. The file that was used to create this example is called plot.csv in the Offline Examples. For details about how to play this on your own PC, read the Sydney BitScope page.

(Re)power the DSO, load this file and what you see is a simple sinewave.

Mode Selectors

This is one half of the signal required to display an X-Y plot. The other is of course channel B, which you can enable now. Now you see a second sinusoid with a period 3 times longer than channel A.

To see the plot (aka lissajous) click the PLOT display selector button.

While similar to the animation, this lissajous is static and not scaled to the entire display. To adjust it to use more display, change each channel's vertical scale:

  1. Select 500mV/Div for Channel A.
  2. Select 500mV/Div for Channel B.
  3. Note that 500mv/Div for Channel B is too much (the lissajous extends beyond the right edge of the display). In this case channel normalize mode adjusts the scale by just the right amount; click the Channel B range parameter to normalize it.
  4. Turn REPEAT off (because it's only one frame and we don't need to continuously update it).

We now have the lissajous as above but it's not rotating. In fact, the rotation in the animation above is due to adjustments made to the waveform offset.

Try adjusting this now and see what happens. The lissajou rotates, but not by much.

This is because at this timebase (50uS/Div) we can adjust the offset (ie, TD) by only a small amount (500uS). However if you look at the animation we're adjusting it by almost 10mS.

To adjust it by more, slow the timebase. In this case, simply click the timebase parameter (to slow it x10). The lissajous will become more dense but the samples themselves more sparse (unless we also happened to choose Raw Data Mode).

Next, click the timebase zoom parameter (to increase it x10) to compensate for the new timebase value, and we're back were we started (50uS/Div) only this time we have 10 times the duration over which to observe the phase relationship between the two sinusoids.

Now when you adjust the waveform offset you will see significant phase changes between the two channels because now we are viewing it over a much longer time.

This example shows a dual channel one-shot capture of two sinusoids which unlike a conventional analog scope is the more common way to view lissajous with BitScope. In fact in many cases an analog scope cannot show changing phase relationships very well, whereas a storage capture with BitScope DSO lets you examine it in fine detail.

Visit the next page (FM Signal) to learn more about the integrated spectrum analyzer.