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3A80.20-Lissajous Figure

Description: This setup demonstrates Lissajous patterns on an oscilloscope.

Equipment:

    • Oscilloscope
    • 2 Function Generators
    • GNO double cable – 2
    • Single cables – 4

Procedure:

  1. Connect the two function generators to the oscilloscope via the output socket to channel 1 and 2 on the oscilloscope .
  2. Settings for the digital oscilloscope:
    • Go to ‘Acquire’ and set the following :
      • XY display – ON
      • Record length – 20K thickness
      • Mode – Hi-resolution
  3. Set both the function generators to equal frequencies (recommended-1000 Hz and 0.2 V). You should see a circle/ellipse on the graph.
  4. Keep changing the frequencies to produce different combinations from the 2 generators to see different patterns.

Concept: A Lissajous curve is the graph produced by two phase-shifted sinusoidal functions, on the X-Y plane. On an oscilloscope this can be viewed in the XY mode with two separate signals inputed into channel one and channel two. Their respective time-varying voltages are displayed as x and y on the graph. As we change the frequency, the phase relationship between the signals is presented as a Lissajous figure.

Tips:

  • Make sure the function generators are producing sine waves (this mode can be changed in the waveform setting)
  • Center the vertical and horizontal positions.

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