Pmod IA with Arduino UNO returning incorrect values.

[Keaton]

Hello, I have a Pmod IA module connected to my Arduino UNO running the example code from this library: https://github.com/mjmeli/arduino-ad5933. However, when I run the code, I get unexpected values. 

The code and calculations for this stuff goes way over my head so I have not modified the code in any way other than to mess around with the REF_RESIST value.

When using a reference resistor of 10kOHMs, after calibration it reads as 10kOHMs. However, if I replace that resistor with a 5k or 20k OHM resistor, it still reads as 10kOHMs, but if I replace it with a 100kOHM resistor, it reads as around 25kOHMs. Interestingly, if I set REF_RESIST to 10k but I calibrate it with a 100k resistor, it reads as 10k, but when I replace it with 200k and 300k resistors, it reads as 20k and 30k, so it seems like SOMETHING is working, although adding a capacitor in the mix to measure complex impedance did not result in the correct value divided by 10. However, if I set REF_RESIST to 100k and try calibrating it with a 100k resistor it reads as -31k or something.

Clearly I am doing something wrong but I am very new to this. I am pretty sure all of my connections are correct so maybe I have to modify the code in some way for my purposes. Any help is appreciated.

[JColvin]

Hi @Keaton,

I apologize for the delay.

I haven't gone through this library specifically, but unfortunately most of the libraries that I've looked at online have some sort of error in their calculations or register manipulations. The Pmod IA has also been retired for quite some time so there isn't a lot of available support for. The best I can do is direct you to this thread: https://forum.digilentinc.com/topic/4375-pmodia-returning-incoherent-impedance-values/?sortby=date.

I'm sorry I couldn't be of a lot more help.

Thanks,
JColvin