6.Demonstration
(7) Turn the Vertical Scale and Vertical Position knobs, optimizing the
waveform.
(8) With the elliptical oscillogram method adopted, observe and calculate the
phase difference (see Figure 6- 6).
Figure 6- 6 Lissajous Graph
Based on the expression sin (q) =A/B or C/D, thereinto, q is the phase
difference angle, and the definitions of A, B, C, and D are shown as the graph
above. As a result, the phase difference angle can be obtained, namely, q =±
arcsin (A/B) or ± arcsin (C/D). If the principal axis of the ellipse is in the I and
III quadrants, the determined phase difference angel should be in the I and IV
quadrants, that is, in the range of (0 - π /2) or (3π / 2 - 2π). If the principal axis
of the ellipse is in the II and IV quadrants, the determined phase difference
angle is in the II and III quadrants, that is, within the range of (π / 2 - π) or (π -
3π /2).
Example 6: Video Signal Trigger
Observe the video circuit of a television, apply the video trigger and obtain the
stable video output signal display.
Video Field Trigger
For the trigger in the video field, carry out operations according to the following
steps:
The signal must be
centered and kept in the
horizontal direction.
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