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jamesbraza

Interpreting Input and Phase in WaveForms Impedance Analyzer

Question

Hello Digilent Forums,

I am a new user of the Analog Discovery 2 + Impedance Analyzer instruments.  I am using WaveForms 3.10.9.  I am trying to understand the metrics for Input and Phase.

In the docs, `impedance.html`, it lists:

  • Input as showing the "DUT/reference resistor".  The Y axis plot is "M Input Gain" with units in dB.
  • Phase as showing the phase angle and Ref RLC input phase.

I am assuming θ ("Phase") is the phase difference seen by the Analog Discovery 2's two scopes between V and I.

Can you please explain more what the terms mean?

  • M ("M Input Gain")
  • ∠ ("Input Phase")

For your reference, I have attached a plot generated using a 100 kΩ resistor and then a 0.1 μF capacitor in series.

Thank you in advance for your help!

InputAndPhase.png

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Hi @jamesbraza

The M (input gain) is Vdut/Vref and the < (input phase) is the phase of DUT output vs input. These are Network Analyzer like measurements.

Since the IA Adapter module uses this circuit M = (VC1-VC2)/VC2

image.png.d3b834b2f048fcf8ef3afc7d2358c320.png

Here you can see in the Time view the captures of Scope channel 1 (yellow) and 2 (blue):

image.thumb.png.70ee136126b5233c8ca41508a1759b06.png

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Thank you again for the response @attila.  That `Time` view comparing the two oscilloscope's voltage measurements is quite useful!

Your response has made me question my understanding of θ ("Phase") vs ∠ ("Input Phase").

To reword what you said above: ∠ = difference (°) between Phase_VC1 and Phase_VC2

What does that make θ?

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Hi @attila,

Okay so I read Test Equity's Application Note and found the below image on pdf page 15 of Keysight's handbook.

Impedance_ParallelSeries.png.44db6e0e761d550db6483015d14b408f.png

So I now understand what θ is, and also now I understand what is the point of having added all the parallel and series channels.

Thank you again for your help!

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