Briefly describe how to measure the phase difference between two signals with an oscilloscope?

Only two signals of the same frequency can have a phase difference.

Put two signals with a dual-trace oscilloscope.

Show them at the same time, and then count the corresponding positions of the two signals (e.g., crest and crest, trough and trough) in the horizontal axis direction x squares, if a period is y squares, then the phase difference between the two signals is: 2 * (x y).

Or you can have the oscilloscope work in X-Y mode and observe Lisajou patterns.

The two signals are not of the same origin, i.e., unrelated, and are measured with a digital oscilloscope.

Input signal A into oscilloscope CH1

Select CH1 as the trigger source

Press the "AutoSet" button, and the A signal will be displayed steadily in the upper and lower centers of the screen.

Signal B is input into the oscilloscope CH2, and since the A and B signals are unrelated, the B signal will move slightly relative to the A signal.

Adjust the amplitude and displacement of the CH2 so that its amplitude is comparable to that of the A signal and centered on the top and bottom of the screen.

Press the "Run Stop" key

Using the Cursor function, move the x1 cursor to the ascending intersection of the A signal and the horizontal line in the center of the screen.

Using the "Cursor" function, move the X2 cursor to the ascending intersection of the B signal and the horizontal line in the center of the screen.

At this time, the numerical display time difference value on the screen is the phase difference between A and B.

The two signals are not homologous, i.e., unrelated, and are measured with an analog-digital oscilloscope (which is more cumbersome, and you have to be quick and quick).

Input signals A and B into the input oscilloscopes CH1 and CH2 respectively

Select CH1 as the trigger source

Adjusting the synchronous trigger level makes the waveform display of the A signal stable, and since the A and B signals are irrelevant, the B signal will move slightly relative to the A signal.

Adjust the amplitude and displacement of CH1 and CH2 respectively so that the amplitude of the A and B signals is comparable, and the screen is centered up and down.

Adjust the horizontal displacement torsion to move the ascending intersection of the A signal and the horizontal line in the center of the screen to the far left (or rightmost) end of the screen.

The coordinates at the ascending intersection of the B signal and the horizontal line in the center of the screen are read, and the coordinate value of the B signal is the phase difference between A and B. Since the B signal moves slightly relative to the A signal, there will be a deviation from each reading, which can be read out multiple times and then averaged.

The two signals are homologous, i.e., correlated, and are measured with a digital oscilloscope.

Input signal A into oscilloscope CH1

Select CH1 as the trigger source

Press the "AutoSet" button, and the A signal will be displayed steadily in the upper and lower centers of the screen.

Input signal B into oscilloscope CH2, and since the A and B signals are related, both signals can be displayed stably.

Adjust the amplitude and displacement of the CH2 so that its amplitude is comparable to that of the A signal and centered on the top and bottom of the screen.

Using the Cursor function, move the x1 cursor to the ascending intersection of the A signal and the horizontal line in the center of the screen.

Using the "Cursor" function, move the X2 cursor to the ascending intersection of the B signal and the horizontal line in the center of the screen.

At this time, the numerical display time difference value on the screen is the phase difference between A and B.

The two signals are homologous, i.e., correlated, and are measured with an analog oscilloscope.

Input signals A and B into the input oscilloscopes CH1 and CH2 respectively

Select CH1 as the trigger source

Adjusting the sync trigger level makes the waveform display of the A signal stable, and since the A and B signals are related, both signals can be displayed stably.

Adjust the amplitude and displacement of CH1 and CH2 respectively so that the amplitude of the A and B signals is comparable, and the screen is centered up and down.

The coordinates of the ascending intersection of the A signal and the B signal and the horizontal line in the center of the screen are read out respectively, and the time difference between the two coordinate values A and the phase difference of B are read.

According to the measured waveform, adjust the x-axis after stabilization, so that the measured waveform is in the whole grid position, and then observe the phase of the two waveforms, which can be calculated.

Select the two-channel interrupted mode, the signal is input CH1 and CH2 separately, and the Y-axis gain is adjusted so that the amplitude of the two signals is the same.

Select CH1 to trigger, if the waveform of CH2 is after CH1, that is, CH2 before CH1's super-large crack circle, observe the time difference of the waveform at the same position, and then compare it with the time of one cycle, we will know the phase difference.

The accuracy of measurement with an oscilloscope is not high.

Foreword Let's first use a signal generator to generate a set of sine wave signals with a phase difference of 30°. In fact, at the beginning, I wanted to use one of my previous 4G mobile phone signal motherboards for demonstration, but after looking for a long time, I couldn't find its power supply, so I used a signal generator to demonstrate.

2. Waveform display.

The software will automatically connect to the oscilloscope, but the waveform will look messy at this point. Well, the first step, click on Set Automatically. The device will take a few seconds to automatically measure the frequency and voltage amplitude of the waveform, and adjust the operating parameters of the oscilloscope.

3. Adjust the waveform display.

The automatically measured waveform looks intuitive, with a noticeable phase difference between the two waveforms.

4. Enable XY mode.

The second step is to click Run XY mode. At this time, the software intuitively shows that the phase difference between the two channels is 30° (330° is a negative phase difference). The XY mode, also known as the Li Shayu pattern pattern, is the superposition of the signal waveform on horizontal and vertical coordinates.

5. Measurement of other waveforms.

Change the scene. We change the signal to 1kHz triangle wave on both sides, and set the phase to 119°.

6. Summary: The measured phase is consistent with that of the signal generator. The frequency is also on the right.

The oscilloscope of freetest is relatively simple in operation, mainly thanks to the Android system.