Table of Contents
Advertisement
35.5. Example 5: Application of X-Y Function
Examine the Phase Difference between Signals of two Channels
Example: Test the phase change of the signal after it passes through a circuit network.
Connect the oscilloscope with the circuit and monitor the input and output signals of the circuit.
For the examination of the input and output of the circuit in the form of X-Y coordinate graph, please operate
according to the following steps:
1.
Set the probe menu attenuation coefficient for 10X and that of the switch in the probe for 10X (see "6. Hot
to Set the Probe Attenuation Coefficient" on page 101).
2.
Connect the probe of channel 1 to the input of the network and that of Channel 2 to the output of the
network.
3.
Push down the Autoset button, with the oscilloscope turning on the signals of the two channels and
displaying them in the screen.
Turn the VOLTS/DIV knob, making the amplitudes of two signals equal in the rough.
4.
5.
Press the Display button and recall the Display menu.
6.
Press the H3 button and choose XY Mode as ON.
The oscilloscope will display the input and terminal characteristics of the network in the Lissajous graph
form.
7.
Turn the VOLTS/DIV and VERTICAL POSITION knobs, optimizing the waveform.
With the elliptical oscillogram method adopted, observe and calculate the phase difference (see Fig. 84).
8.
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 angle is in the II
and III quadrants, that is, within the range of (π / 2 ~π) or (π ~3π /2).
The signal must be centered
and kept in the horizontal
direction.
Fig. 84 Lissajous Graph
-164-
Hide quick links:
Advertisement
Table of Contents
