Tel: 886.2.2175 2930 Email: [email protected]
www.salukitec.com
62
6.5
Example 5: Using X-Y Mode
Viewing Phase Differences between Two Channel Signals
For example, you need to measure the change in a phase across a circuit network.
Connect the oscilloscope with circuitry and view the input and output of the circuit in XY mode. Follow the steps
below.
1.
First, prepare two oscilloscope probes and set the switches to 10X on both probes.
2.
Push the CH1 MENU button and set the Probe option attenuation to 10X; push the CH2 MENU button and set
the Probe option attenuation to 10X.
3.
Connect the CH1 probe to the input of the network, and connect the CH2 probe to the output.
4.
Push the AUTOSET button.
5.
Turn the VOLTS/DIV knobs to display approximately the same amplitude signals on each channel.
6.
Push the DISPLAY button to see the Display menu.
7.
Push the Format option button and select XY.
8.
Now the oscilloscope displays a Lissajous pattern to characterize the input and output of the circuit.
9.
Turn the VOLTS/DIV and VERTICAL POSITION knobs to properly scale the waveform display.
10.
Use the Lissajous's oscillographic method to observe and calculate the phase differences following the formula
below.
As sinθ=A/B or C/D, in which θ is the phase difference angle between channels and A, B, C, D represent what
shown in the figure below, you can get the value of the phase difference angle by the formula: θ=±arcsin(A/B) or
±arcsin(C/D).
If the principal axes of the ellipse are in the first and third quadrants, the phase difference angle should be in the first
and fourth quadrants, i.e. within (0~π/2) or (3π/2~2π). If the principal axes of the ellipse are in the second and fourth
quadrants, the phase difference angle should be in the second and third quadrants, i.e. within (π/2~π) or (π-3π/2).
See the figure below for better understanding.
