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9. Using the elliptic oscilloscope display graph to observe, measure and calculate the
phase difference. (See the figure below)
The signal must be horizontally center
Figure 3-7 Lissajous figure
If sin θ = A
or C
B D ,
θ is the angle of disparity between the channels. For definitions of A, B, C, D see the
above figure. Calculating with this formula, the angle of disparity is
θ = ±arcsin (A
) or θ = ±arcsin (C ).
B D
If the elliptic main axis is within quadrants I and III, the angle of disparity should be
within quadrants I and IV, i.e. inside (0~ π) or (3π ~ 2π).
2 2
If the main axis is within quadrants II and IV, the angle of disparity should be within
quadrants II and III, i.e. inside (π ~ π) or (π ~ 3π).
2 2
Furthermore, if the frequencies and phase differences of two signals being measured are
exact multiples, you can calculate the frequency and phase correlation between the two
signals.
10. X-Y Phase difference table :
Signal Phase difference
frequency
ratio
0° 45° 90° 180° 270° 360°
1:1
Illustration 7: Video signal triggering
To observe an individual video circuit, use the video trigger function to obtain a stable
display of video output signal.
Video field triggering
To trigger in the video field, follow the steps below:
1. Press [TRIGGER] to display the trigger menu.
2. Press [F1] to set the type to video.
3. Press [F2] to set trigger source to A.
4. Press [F3] select PAL as the video standard.
5. Press [F4] to select odd field or even field synchronization.
6. Adjust the horizontal time base for a clear waveform display.