[werk_ag]

Hi,
I have some false reading sometime on the SHT71!
Perhaps it's because the Vdd supply should be 3.3V ?
Do you think i can take the 3.3V from the Nano ?

Be aware that the supplied SHT1x library use coefficients for a sensor powered by 5V.
Those coefficients are used to calculi temperature and humidity.

If you are using the bare SHT75 maybe you should use some decoupling caps on the power lines.