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AD2 Network analyser


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Dear experts,

May I know how the AD2 waveform 15 calculates the phase difference in the bode plot of network analyser?

And how does the averaging/average function works? Does it help decrease my signal noise or is there anyway/functions to have a more accurate phase difference reading?

I attached a picture, and I would like to ask if the AD2 is able to capture the phase difference between this 2 signal or is it too noisy?

 

Thanks a lot for reading!

Screenshot_20211111-214648_Samsung Notes.jpg

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Hi @attila

Thanks for the clarification!

Looking at the related post I do see coherent averaging does improve the accuracy especially when there is huge noise of the same frequency interfering the signal. But this leads me to a question of which case should I use which averaging or is it in all cases the coherent averaging is better?

In your reply to my question, you showed a very small signal with noise may I know how you created that signal in AD2 and what is the SNR of that signal? It seems that with that small signal it is still able to get a decent bode plot which increase my confidence in measuring the phase of my signal example.

Lastly, may I ask what is the maximum current output when using network/wavegen as I see in documents it is 10mA and it says it varies. Does using the 5V auxiliary power supply increases its output current?

Thanks alot for your time!

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Hi @Malcolm

The Wavegen drive is 10-50mA depending on voltage level, at +/-5V min 10mA and around 0V max 50mA.
The aux/usb supplying affects only the power supply limits.

image.png.2c7aa57a6a9ce6567d52f08d234c6bf9.png

 

The coherent averaging looks to be slightly better with fixed frequency noise.
In the following pic R1-2 uses coherent average which perfectly overlaps C1-2 using mag/phase.

The 10mV signal is generated by W1 controlled by NA. The C1 SNR is 20...10dB and C2 -40..0dB.

image.thumb.png.5a16cb7352b529871d03c470a52112bc.png


 

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@MalcolmBased on my adventures using the NA, I'm very confident that it should give you reliable results for the scenario shown in your screenshot, especially because I can still rather easily see the sine wave in the response by eye and can pull out a phase difference if really required. I've seen the AD pull out reasonable mag/phase from a lot worse time traces!

The only thing that is a bit borderline (but probably still acceptable) is the amplitude of the blue channel being only a few mV. For your scenario, this should still work, but to improve the measurement it'd be advantageous to either increase the excitation amplitude if you can (i.e. if there isn't any non-linearity limiting you), or using a pre-amplifier before the AD to get the voltage amplitude up into a decent range.

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Hi @attila

Thanks for the information and detailed analysis! I will try and implement AD2 to my set up and hope it works.

 

Hi @Robin Oswald

Saw your post on coherence averaging and it allowed me to learn a new topic! Thanks to you and @attila , I may try out the beta version for my experiment. 

Thanks for your suggestion, yes I was thinking of using a pre-amplifier, although I am hoping to not add it in first as the accuracy of my experiment relies on an accurate phase information, hence I will try to minimise any components that may add phase noise or too much phase shift. But will add it in when signal is deemed to weak :D.

Once again thank you both for the help and input.

 

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