Difference Between Python Plot and WaveForms Plot on C-V Measurements

[Resul]

Hi All,

I am developing a custom application using Analog Discovery 2 and Impedance Analyzer Adapter. I am trying to implement C-V measurements.

WaveForms chart is different from my application with the same parameters. I wanted to investigate the difference with writing python scripts which is the same logic with my custom application. 

Here is the WaveForms screenshot with the same DUT configuration and Python script plot. They have some configurations but the plots are so different. Peaks are similar. But, They look really different. 

DUT: 1N4007 Diode. 

What is the reason for the difference between charts? WaveForms charts are smooth. Do WaveForms have extra configuration or techniques under the hood? 
 

Please see the charts and the script file. 

Regards,

Resul 

AnalogImpedance_CV.py

[attila]

Hi @Resul

The bugs mentioned yesterday are fixed here:
https://forum.digilentinc.com/topic/8908-waveforms-beta-download/

Your code will work if you use c_int in FDwfAnalogImpedancePeriodSet

See the examples AnalogImpedance_OffsetSweep.py AnalogImpedance_OffsetSweepCp.py which also look for out of range conditions on Scope inputs.

 

 

[Resul]

Hi Mr. @attila,

Thanks for your great efforts and new software version. My type error in FDwfAnalogImpedancePeriodSet is really annoying for me. But, No problem. I feel lucky with these two informative scripts.

1. AnalogImpedance_OffsetSweepCp.py is ok. Plots are same now. I changed my custom application code according to this scipt and my problem is solved.

2. AnalogImpedance_OffsetSweep.py is ok. I tested and it is working -4V to +4V. How can we extend to range from -10V to +10V? if it is not applicable with some limitations as you shared before. What is the maximum range applicable? I am seeing a limitation on -5.2V and +5.2V on multimeter.

Regards,

Resul 

 

[attila]

Hi @Resul

The Wavegen can output -5V to +5V. There is some reserve like +/-0.4V but this is not guaranteed to work on each device or with proper linearity.

You may do +/-10V using +/-5V rails as reference instead of ground.
- with -5V doing sweep from -5V to +5V which will be relative 0 to +10V
- with +5V sweep from +5V to -5V will be like 0 to -10V
Note that you could do this with minimal amplitude like 0.1V (or 0.2V) to limit the Wavegen amplitude to +/-5.1V
or use +/-4V reference with 1V amplitude signal for +/-8V range.
see point 3 :