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This is a popular software for those people who don't have a real oscilloscope or function generator: https://www.zeitnitz.eu/scope_en

If anyone tried it before, would you answer my questions, please?

1.What is x-y graph? What does each axis represent?

  1. How Can I measure the frequency of a signal that is composed of two frequencies? such as: resonant frequency or harmonics.

Thank you very much,

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    \$\begingroup\$ Exactly what it says on the tin. Each channel. Get better software. \$\endgroup\$ Jan 9, 2016 at 17:04
  • \$\begingroup\$ @IgnacioVazquez-Abrams Would you suggest a better software, Please? \$\endgroup\$ Jan 9, 2016 at 17:09
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    \$\begingroup\$ The software has a tab "frequencies". I've no screenshot, but this tab should show a diagram showing how much of which frequency is in the signal. This is exactly what you're searching for. \$\endgroup\$
    – sweber
    Jan 10, 2016 at 13:13

2 Answers 2

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What is x-y graph? What does each axis represent?

XY mode is used when you have two inputs (channel 1 and channel 2) and you want to represent the phase relationship between them differently: -

enter image description here

Typical is when Y lags X by 90 degrees and is the same frequency - it produces a circle as per the top line above. Channel 1 normally drives the Y axis and channel 2 drives the X axis.

This function is available on most o-scopes.

How Can I measure the frequency of a signal that is composed of two frequencies? such as: resonant frequency or harmonics.

It's tricky with a normal scope and I'd tend to use a spectrum analyser for this if accuracy is required. Having said that, if the input is a waveform that is harmonic rich then a scope can be used to fairly accurately determine the fundamental frequency - think of a square wave - it contains an infinite series of harmonics but nobody has much problem determining the fundamental frequency: -

enter image description here

The square wave above (black) is running at 1 kHz because the timebase is 1 milliseconds for each cycle. Having said all that it appears that the sound card software in the question has this feature: -

Frequency analysis (Fourier spectrum)

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To answer your question on X-Y mode (which is an independent question in its own right):

For a scope, the X (horizontal axis) is normally time, and the Y (vertical axis) is normally voltage (for the purists, amplitude as it may be current with the appropriate probe).

In X-Y mode, 2 signals are applied and the X axis is no longer time, but the amplitude of (usually) channel 1, and the Y axis is now the amplitude of channel 2.

This gives rise to a Lissajous figure whch can effectively show complex relationships between 2 signals such as harmonics and phase.

Video tutorial

Update: Added a common use:

X-Y mode is commonly used in Analog signature analysis on Flying probe test stations.

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