User Manual of Smart Digital Storage Oscilloscope
78
waveform.
(8)
With the elliptical oscillogram method adopted, observe and calculate the phase
difference (see
Fig.6-6
).
Fig.6-6
Lissajous Graph
Based on the expression
sin q =A/B or C/D
, there into,
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:
(1)
Press the
Trigger Menu
button to display the trigger menu.
The signal must be
centered and kept in the
horizontal direction.