I encountered a positive problem: the perfomance is probably better than my measurement equipment! namely, I tested 5 different mobile/PC based tools and got quite different results.
For the sake of simplicity, I recorded a short video of Peterson products I have. To my surprise, the E string result varies 0..-14c using these tools. Makes me ask a question how can I validate my setup if the measurement accuracy is so bad?
As a computer / digital design engineer, I assume the processor load/ oscillator variance / windows / Android etc peculiarities may affect the results, and I am thinking the most accurate one is the dedicated portable Peterson tuner. Which, unfortunately, does not show any cent scale differences

What do you use to validate your intonation?
https://youtu.be/ryqI5HT07CI
Jani