8.Demonstration
127
CH4.
(4)
Push the
Autoset
button, with the oscilloscope turning on the signals of
the two channels and displaying them in the screen.
(5)
Push
CH1
button to select CH1, turn the
Vertical
Scale
knob, and then
push
CH2
button to select CH2, turn the
Vertical
Scale
knob, making the
amplitudes of two signals equal in the rough.
(6)
Push the
Display
button and recall the Display menu.
(7)
Select
XY Mode
in the bottom menu. Select
Enable
as
ON
in the right
menu. The oscilloscope will display the input and terminal characteristics
of the network in the Lissajous graph form.
(8)
Turn the
Vertical Scale
and
Vertical Position
knobs, optimizing the
waveform.
(9)
With the elliptical oscillogram method adopted, observe and calculate the
Figure 8-6 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
The signal must be
centered and kept in the
horizontal direction.