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Applications
19
50c/s
100 c/s
150c/s
75 c/s
Fig. 6. Examples of Lissajous figures
Phase measurements
Phase angles can be measured by means of a Lissajous figure (ellipse)
The image must then lie symmetrically round the centre.
The following applies irrespective of the quadrant in which the phase
angle is found: the sine of phase angle <p is determined by the ratio a/b
(see Fig. 7).
In the figure, sine <p — 2 div./4 div. — 0.5. The phase angle <p is then 30°.
If the top of the ellipse is at the right of the screen, the phase angle is in
the first quadrant (30°) or in the fourth quadrant (360°-30° = 330°).
P£M 290
E12J
Fig. 7. Determining the phase angles sine <p = a/b
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