After Jürgen shared his direct transducer pot output approach with linear output conclusion, I knew my log results might have be premature but that was the output I first got. This somewhat logarithmic sidestick story fitted so well and everyone I consulted with somehow agreed to it so I started solving the log output with curve software instead of checking the rest of possible transducer pot pins!
There was a good chance for linear output on other pins but I thought I would deal with that later when I will fly more! That is also why I didn’t make the Sidestick pinout yet. I should have spent more time with outputs the first time. I highly doubt it but I am really sorry if I somehow discourage anybothy of acquiring sidesticks with genuine transducers.
Any way with this productive debate another lesson was learned. I really appreciate inputs like that so I went back to sidestick and this time I removed the transducer covers and went with direct pot output approach. Of course it turned out that I also have the same Vishay 10kΩ multi pots inside with four connectors per pot (Vref, signal/wiper, ground and middle ground). I only had to find the right pins at the end of the six plug cables. Inside the side consoles there are also useful sidestick cable attachments plugs.
You can find the sidestick and transducer pinout here.
I also traced my “wrong” log signal pins back to transducer pot and found out that my ground went to that forth middle ground pot connector. Not sure how I missed that! In one connection case there is a resistor incorporated which could change output function and is currently the main suspect to be examined.
Thank you again Jürgen for sharing your thoughts and doubts.
However, even if signal is linear I still think A320 FBW programs need some sort of sensitivity curve settings for fine tuning flight controls.