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JamieJ

Impedance for Analog Discover 2 itself?

Question

Hello 

I am an Electrical Engineering student who just finished the second year last April and I have a question about Analog Discovery 2. I wasn't sure about the forum topic that I had to choose, so I chose this forum to ask my question. Hopefully, this is the right one.

I wanted to measure the impedance of AD2 itself to make a lab to understand AC power matching concept.

Do I need the impedance of  AD2 for me to make this kind of lab? If so, how can I measure it? I have no idea how I can connect AD2 to some other wave generator, so I can measure the voltage drop through AD2.

I read the reference manual of AD2 and I couldn't find any information, so I leave here my question.

I would really appreciate any wisdom!

Thank you.

 

 

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Hi @JamieJ,

Welcome to the Digilent Forums!

I moved your thread to a section where more AD2 experienced engineers look.

best regards,

Jon

 

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Hi @JamieJ,

I don't know the full answer to your question (the engineer much familiar with this will be able to respond when they get back into the office after the weekend), but there is some information about the impedance of the Analog Discovery 2 on this thread here.

Thanks,
JColvin

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Hi,

most likely, your test instrument has such high input impedance (1 MOhm / 24 pF according to the product webpage) that it does not affect a typical measurement.

Now in case it does, the first thought is use a 10:1 scope probe (as found in a typical lab), to avoid loading the source.

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Hi @JamieJ

The Impedance Analyzer tool in WaveForms application takes in consideration the probe impedance (R/C) when it calculates the DUT characteristics like: phase, impedance, admittance, capacitance...
The auto value for Analog Discovery 2 assumes 43pF/1.04MΩ Approximately such probe impedance you get with wire harness or with the Impedance Analyzer Adapter module. 
This is important when measuring low impedance values like pF capacitors. For such measurement it is also important to perform at least open compensation.

image.png.071131acf78164aa7363632c159f3d9b.png

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@attila Thank you for the detailed explanation!

I would like to ask you one more to check if I understand correctly if it is okay with you.

So, when I use Impedance Analyzer of Analog Discovery 2, AD2 automatically assumes the probe of its own has 43pF/1.04MΩ. Is it correct? 

If I use Wavegen as my voltage source, does it not have any impedance of the voltage source? 

 

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Hi @JamieJ

Yes, AD2 43pF/1.04M

The AWG output of the AD/AD2 has theoretically zero impedance.
The signal source quality/impedance is not important since the measurements in the Network Analyzer by default use the difference between Scope inputs 1 and 2.
The Impedance Analyzer fine tunes the above relative measurements taking in account the scope probe impedance as well the optional open/short compensations.

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