Has anybody experience with MODBUS to read temp sensors?

[Rudy M]

Hi Petr, 
I did some more testing and discovered that I need to add the user "rudy" to the "dialout" group again. 
As you wrote, "Typical error on Mint/Ubuntu." 

So, I ran the Terminal command you suggested: 
sudo usermod -a -G dialout $user (in my case, $user = rudy). 
-Turn off the PT100 module's power supply and turn it back on after 20-30 seconds. 
-Turn the PC off and back on (or restart it). 
And the PT100 routines are working perfectly again! 
Regards,
Rudy