[Impedance Analyzer adapter: why the constant voltage mode turn the resistor alarm on?]

And now... Something less conceptual.

We need to fix 10mV between the DUT in all the samples along the frequency range we measure (1Hz to 1MHz).  
Then our DUT may change the impedance a lot along the frequency range and so we need to adjust both amplitude and the resistor (that's why we are trying so hard with the Impedance Analyzer).

I will try this:

const Voltage = 0.01 // desired VRMS
const MaxAmplitude = 2.5 // maximum AWG amplitude   
/*#######  Is this still available "The AWG output range (Offset + - Amplitude) of Analog Discovery 1 & 2 is guaranteed between -5V and +5V"?
from: https://forum.digilentinc.com/topic/2364-squarewave-amplitude-error/?do=findComment&comment=8122*/

if(Amplitude==0) { // first step, initialize 
    Resistor = 1e5        /*chanched 1e6 for 1e5*/
    Amplitude = Voltage*Math.SQRT2
    Repeat = 2 // repeat step twice
}
else{ // adjust amplitude based on VRMS
    Amplitude *= Voltage/VRMS
    if(Frecuency==10){
        Resistor = 5e4
        Repeat = 2 // repeat step twice
    }if(Frecuency==50){ 
        Resistor = 1e4
        Repeat = 2 // repeat step twice
    }if(Frecuency==500){ 
        Resistor = 1e3
        Repeat = 2 // repeat step twice
                    
    }else if(Repeat){
        Repeat--
    }else{
        Repeat = 1 // do each step twice, to adjust and measure
    }
}

For this excercise:

On 8/26/2021 at 12:32 PM, EzeStare said:

it as before

Can you say me if you look this legitimate?

 

[Impedance Analyzer adapter: why the constant voltage mode turn the resistor alarm on?]

Many, MANY thanks. You have solved many doubts I had. 

It's not the same just to thinks it is that way than to be instructed. 

Let me ask you some more about the things that I already asked and a little more.

1- I understood that if I use the Custom Mode and "constant voltage" example with the Impedace Analyzer the resistor will NOT change automatically. But, it means that if I use "Constat Voltage Adapter" intead, the Impedance Analyzer will change the reference resistor automatically. Right?

So, if I use something like (just to say something)

if(Amplitud==10000) {Resistor=10000}

 the Impedance Analyser will set the reference resistor at 10 kOhm if an Amplitude equal to 10000 is detected. 

2-Is my interpretation correct?

14 hours ago, attila said:

The Scope C2 measures the voltage on this Resistor thus giving the current.

5. The VRMS variable is the measured Vrms. The Voltage is a constant in the code.

4-About this: How is the "VRMS" value measured? Is it the voltage value on C2 or it is the calculated C1-C2 difference value? 

5-If I understood correctly the "Aplitude" variable is just a value calculated from "Voltage" and "VRMS". It is defined "Amplitude=0"  before the EIS start (so the first "if" is executed)?

 

[Impedance Analyzer adapter: why the constant voltage mode turn the resistor alarm on?]

First of all. Thank @attila you for yout prompt responses. Both times.

And of course, hi.

About the usage of a Custom script or another. I used "Constat Voltage Adapter" assuming that if I connet the Impedance Analyser this onse should be the correct.

1-Are you saying that even if I connect the Impedance Analyzer I should hace used the Custom Script "Constat Voltage"?

 

 

Well, even I used the wrong Custom Script it could help me to ask you some doubts.

So ... if I understar correctly you are saying that with the script I can't control how the Impedance Analyzer select the resistance. Right?
therefore, if I use this code as an example:

2-Is this code the exactly one that makes de option "constat voltage" works? (when IA is connected)

Secondly, if I change:

   3-Resistor: Am I just changing the value of the measured resistance? (Measured by the c2). And this measured resistance is the one measured with the c2. Right?

   4-If i undertood correctly the previous point: like the Resistor variable, are modification applied to Amplitude just a modification on a measured value? (by c2)

   5-Voltage is the desired VRMS. But what about VRMS variable? where is it declared and defined?

   6-Finally, what is the Repeat varible used for?

 

[Impedance Analyzer adapter: why the constant voltage mode turn the resistor alarm on?]

Oh! Forgot to add those.

First try

Same RC circuit as before

Same Randles circuit as before

 

Second Try

Same RC circuit as before

Same Randles circuit as before

 

[............]

There are more, but these should be enought. 

The point is: if the Impedance Analyzer is suposed to give a better EIS experience, then why its worst than without the IA?

I mean, the alarms are not the only thing. Even in the post processed data Error values tends to be bigger with IA than without it. Sometimes this difference this absurdly bigger.

 

[Impedance Analyzer adapter: why the constant voltage mode turn the resistor alarm on?]

The impedance Analyzer description said  “The Impedance Analyzer for Analog Discovery provides automatically adjusting reference resistors and relays, so that reference circuits don't have to be manually built for each test. “

When we used the IA and "constant voltage" mode, the alarms turn on more than we have expected

Here, we show the impedance behavior of the same DUT (RC circuit), using the constant voltage mode (10 mV), with or without the impedance Analyzer adapter, alternatively.

When we used the W1-C1-DUT-C2-R2-GND configuration (without the adapter) with external 4,7kOhm reference resistor, the resistor alarm was turn off for all the frequency range. While, when we used the adapter (with six internal reference resistors), the “resistor too High” alarm turned on in almost all the frequency range.

why the constant voltage mode turn the resistor alarm on? 

How can we solve the resistor alarm using adapter and constant voltage mode?

WITHOUT Impedance Analyzer adapter using the W1-C1-DUT-C2-R2-GND configuration. The external reference resistor was

 

WITH  Impedance Analyzer adapter

[EIS Experimentation with AD2-IA]

Hi Attila, thank you very much for your answer. 

1- Thanks. I had already read it, but we have doubts whether it is possible. 

2- I explain it better, because I think the question is not very precise.

Using  the Impedance Analyzer, when I set the Adapter Option, the resistor is restricted  to the user modification:

At online reference manual it said: The Impedance Analyzer Instrument in WaveForms is made easier to use by the reference resistors and relays that come pre-loaded on the Impedance Analyzer board. The Analog Discovery can automatically select the most appropriate component for the job that it needs to do. 

For the AD2-IA and ‘Adaptar’ configuration at WaveForm, I want to know:

a ) HOW it automatically selects the reference resistor?

b) Is the resistor changed automatically every time the software thinks it is necessary along ONE RUN? Or is it the same during the “run”? (For example, it may select 1 MOhm, since 1 Hz till 1 kHz, and 1 Ohm since 1kHz till 100 kHz)

c) is the resulting graph (BODE) corresponding to the impedance behaviour of the: ‘DUT’ or the ‘DUT + reference resistor arrangement’ system? 

 Thank you
best regards

[EIS Experimentation with AD2-IA]

Hello.

We are working in a research project about electrochemical non-faradic biosensors development. Similar to the forum question made by Borges Cleaver (AD2 as a Electrochemical Impedance Meter: Is possible?) we want to characterize our systems by EIS technique, using the digilent AD2-IA. We can avoid the reference electrode because the non-faradic nature of our electrochemical system.

We have some questions that are difficult to solve reading the manuals or the forum (may be, we miss something of course).

Indeed:
1- In order to select the wires to adapt the system impedance correctly. What is the real value of the impedance at the Wave Generator?

2- If we set the Adapter (IA) configuration to perform an impedance analyzer measure (BODE). It automatically fixed only ONE resistor during all the measure or it may be changing among the time?

3- Taking into consideration that yielded wires could be better in order to avoid noise (inductive and capacitive) in the frequency-dependent DUT impedance measurement, why the IA was builded without BNC connector (for example)? Does Digilent offer some alternative solution or recommendation to this topic?