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Example 5: Application of the X-Y function
Examining the phase difference between the signals of both channels
Example: Testing the phase change of a signal after passing through a circuit.
The X-Y mode is very useful for checking the phase shift of two connected signals. This example shows you
step by step how to check the phase change of the signal after it has passed through a certain circuit. The
input and output signals of the circuit are used as source signals.
Please proceed as follows to view the input and output of the circuit in the form of an X-Y coordinate curve:
1. Set the probe attenuation to 10X in the menu and also to 10X with the switch on the probe.
2. Connect the probe of channel 1 to the input and the probe of channel 2 to the output of the circuit.
3. Switch on channel CH1 and CH2.
4. Press the Autoset key. The oscilloscope switches on the signals of the two channels and displays them
on the screen.
5. Adjust the two signals to approximately the same amplitude with the Vertical Scale adjustment knob.
6. Press the display key to call up the menu.
7. Switch XY Mode to ON with the button.
8. The oscilloscope displays the input and output signals of the circuit as a Lissajous figure.
9. Use the Vertical Scale and Vertical Position knobs to optimise the waveform.
10. Observe and calculate the phase difference using the elliptical oscillogram method.
Image: Lissajous figure
Based on the expression sin(q) =A/B or C/D, q is the phase angle difference and the definitions of A, B, C
and D are illustrated in the diagram above. As a result, the phase angle difference can be determined, namely
q = ± arcsin (A/B ) or ± arcsin (C/D). If the major axis of the ellipse is in quadrants I and III, the determined
phase angle difference should be in quadrants I and IV, i.e. in the range (0 ~ π /2) or (3πc / 2 ~ 2π). If the
major axis of the ellipse is in quadrants II and IV, the determined phase angle difference should be in
quadrants II and III, i.e. in the range (π / 2 ~ π) or (π ~ 3π /2).