How to set CC/CV mode with code?

[Resul]

Hello,

I can successfully communicate with my Analog Discovery 2 device. I can send and receive data. 

I want to build a custom LCR Meter using Analog Discovery 2 and Impedance Analyzer Adapter with C#.

I need CC/CV measurements too. Waveforms have built-in support for these measurements. But, I inspect the Waveforms SDK Reference Manual and all scripts in the Examples folder. I can not find a clue to how to achieve my goal.

I want to learn how can we set "mode" with code. There is only the FDwfAnalogImpedanceAmplitudeSet function. There is also a "Custom" mode. There are five scripts that are

1. Constant Voltage Adapter
2. Constant Current Adapter
3. Constant Voltage
4. Constant Current
5. Offset Sweep

I am using IA Adapter. So, I investigate Constant Voltage Adapter and Constant Current Adapter scripts. I think I need to use these scripts as a reference. But, these scripts use some variables such as VRMS, IRMS.

I see the function to retrieve Voltage and Current. But, I need VRMS and IRMS values. How can I read these values from the device? They are built-in in scripts.

Thanks In Advance, Regards
Resul 

Edited August 24, 2021 by Resul
Change Title

[attila]

Hi @Resul

There is no API for the CC/CV mode. These can be implemented in custom app similar to the example scripts in the WF app/ Imedance/ Mode: Custom, Custom Amplitude

See the dwf.h for Vrms...
The cs and vb will be updated in next version.

    public const int DwfAnalogImpedanceVrms = 14; // Vrms
    public const int DwfAnalogImpedanceVreal = 15; // V real
    public const int DwfAnalogImpedanceVimag = 16; // V imag
    public const int DwfAnalogImpedanceIrms = 17; // Irms
    public const int DwfAnalogImpedanceIreal = 18; // I real
    public const int DwfAnalogImpedanceIimag = 19; // I imag

 

[attila]

Hi @Resul

I think you could use the FDwfAnalogImpedanceStatusInput example: AnalogNetwork_Analyzer.py

dwf.FDwfAnalogImpedanceStatusInput(hdwf, c_int(0), byref(gain1), 0) # relative to FDwfAnalogImpedanceAmplitudeSet Amplitude/C1
dwf.FDwfAnalogImpedanceStatusInput(hdwf, c_int(1), byref(gain2), byref(phase2)) # relative to Channel 1, C1/C#

For mode 0 (W1-C1-DUT-C2-R-GND) or 8 (AD IA adapter) :

gain1 = Amp/VrmsC1
gain2 = VrmsC1/VrmsC2

VrmsC1 = A/gain1
VrmsC2 = A/gain1/gain2

Vrms = VrmsC1-VrmsC2
Irms = VrmsC2/Res

Edit:
Next software version will add such measurement options for the API.

Edited August 9, 2021 by attila

[JColvin]

Hi @Resul,

I believe this change is implemented starting with beta version 3.16.33: https://forum.digilentinc.com/topic/8908-waveforms-beta-download/.

Let us know how this goes for you.

Thanks,
JColvin

 

[Resul]

Hello Mr. Attila,

Thanks a lot for your clear explanation and guidance. I wrote the C# function as in the script in Waveforms. I will inform you after the test with the reference component. 

I am calling the function after each measurement on target frequency. The function calculates the new amplitude and resistor values. After that, I am setting the new values using 
FDwfAnalogImpedanceReferenceSet and FDwfAnalogImpedanceAmplitudeSet functions. 

I hope this is the right approach. 
 

[Resul]

Hello Mr. Attila,

This is a great news. Could you share estimated date for next software version of the API?

Regards

Resul 

 

 

[Resul]

Hi Mr. JColvin,

Thanks for your response. I visited the shared link.  I installed and tried the 3.16.34 version.

After my detailed investigation of dwf.cs class. I come up with these results: 
1. There is a FDwfAnalogImpedanceModeSet function. But, this function does not set Mode (Amplitude, CV, CC, and Custom). This function sets Order which is the measurement circuit. There is a comment in the dwf.cs file.  

2. I think, Mr. Attila did not release the expected API yet. 

Regards,

Resul 

[Resul]

Thank you so much Mr. @attila, Now, I can read Vrms and Irms values without make any math calculation. So, this is more clear for me. I implemented the script logic. I hope they will work. I will test it. 

Thanks In Advance,

Resul 

 

 

[Chris Marcellino]

Hi! Sorry to intrude. Is the recommended way to achieve a constant current mode for impedance measurement still using the above code or is there a more direct API? It sounds like that was being considered? Thank you!

[attila]

Hi @Chris Marcellino

The Impedance Analyzer uses AWG channel/voltage driver so the constant current mode can be implemented in custom software/script like it is in the application's example: