impedance analyzer Impedance Analyzer: What is Parallel Model and Series Model

[jamesbraza]

I am a new user and am trying to understand what all the knobs in this program are for.

I have an Analog Discovery 2 + Impedance Analyzer board.

In `impedance.html` of the documentation, it talks about series resistance/reactance and parallel resistance/reactance.  However, it never actually defines what these address.  The same thing goes for the Meter's parameters for series model and parallel model.

What do these terms refer to? Is it some hardware configuration within the AD2?  There seems to be no documentation of these terms, despite me searching through this forum.

Thank you in advance for your help!

-James

[JColvin]

Hi @jamesbraza,

The series vs parallel values for resistance/reactance/inductance/etc refer to the device or system you are measuring these traits of, i.e. are the resistors and/or capacitors arranged in a series configuration or are they arranged in a parallel configuration. The reason both are listed in the Impedance tool is because the WaveForms software does not know how the device under test (the DUT block shown in the images of the 'impedance.html' page) is organized since it just applies a waveform and compares what the two oscilloscope channels see as the response and performs a variety of calculations to get the values you see in the Meter and Analyzer views.

Let me know if you have any questions about this.

Thanks,
JColvin

[jamesbraza]

Okay that makes sense, thank you for your answer @JColvin

The heart of my question is confusion about why we tell WaveForms this information, if

37 minutes ago, JColvin said:

it just applies a waveform and compares what the two oscilloscope channels see as the response and performs a variety of calculations to get the values you see in the Meter and Analyzer views

In other words:

• What is the purpose of marking as series or parallel?
• Does WaveForms do additional computations with this information?
• What if my DUT has multiple inductors/capacitors in a network, such that they are sort of both in a series/parallel arrangement?

Also, how does the use of the Element parameter tie into this?

• For example, what is the difference between marking `Auto` and `Capacitance`?
• What would happen if I have an inductor in series with a capacitor, and then marked the Element as `Capacitance`?

Regardless, thank you again for your above answer.

[JColvin]

Hi @jamesbraza,

I'm not an expert on the internal workings of WaveForms (that'll be @attila) but I'll see if I can answer your questions:

• What is the purpose of marking as series or parallel -- The purpose of looking at the series or parallel configuration is because you will get different results depending on the configuration; this website illustrates this for a set of 3 capacitors.
• Does WaveForms do additional computations with this information? -- Aside from the other impedance things that can be calculated (admittance, inductance, etc), I don't believe it does anything else.
• What if my DUT has multiple inductors/capacitors in a network, such that they are sort of both in a series/parallel arrangement? -- Generally, I imagine if you were interested in the individual sections you would measure them separately. Admittedly, I'm not certain the best way to consider an overall system if you are just treating it as a black box though.
• With regards to the Element parameter, I'm not certain.

I would also recommend looking at this thread for some additional details.

Thank you,
JColvin

 

[jamesbraza]

@JColvin thank you again for answering!  I read in the other posting as well, and found it useful!

Here is what I meant by my parallel vs series question:

I set up my DUT to be a 100 kΩ resistor and then a 0.1 μF capacitor in series.  I ran the Impedance Analyzer for a single run.  I have attached a screenshot of my result, Impedance view.

You can see the Xp and Xs values are very different.

My thoughts are:

• WaveForms doesn't know what the DUT is, whether it was a parallel or series setup.  All it knows is what was measured across the J2 connector's pins.
• However, WaveForms is reporting very different reactances for a so-called "parallel" and "series" set up.
• So what does WaveForms mean by Xs and Xp?  Clearly it's doing some different processing to make these plots

Thank you again in advance.  I am going to @attila since you did so above for WaveForms questions.

[attila]

Hi @jamesbraza

Yes, you are right.
The application, the IA measures the DUT relative to a reference resistor, using the Scope Channel 1 vs 2 inputs. 
From this it can calculate the voltage/current. Taking in consideration the scope probe impedance and open/short compensation can calculate further values: impedance Z/Rs/Xs (Rp/Xp rarely used); admittance Y/Gp/Bp (Gs/Bs rarely used); series or parallel equivalent inductance or capacitance...

See the following documents:
https://cdn.testequity.com/documents/pdf/series-parallel-impedance-parameters-an.pdf
1.6 Equivalent circuit models of components, page 13 :
https://literature.cdn.keysight.com/litweb/pdf/5950-3000.pdf

[jamesbraza]

@attila @JColvin thank you for your answers!

As I understand more about this software, I come to think you guys are doing something great - making impedance measurement more accessible

-James Braza