ESP32-S2 devkit reading full scale with 2,6v

[HantraxHat]

Hi,
I'm a new happy owner of an ESP32-S2-DevKitC-1.
I'm trying to read the analog value from a soil moisture sensor but i have values that does not correspond with the voltage measuered on the sensor with a multimeter.
I tried also changing the resolution and gpio (5 and 6) but no way, with 2.6v the esp32 is reading full scale. What may be the issue?
Thanks

in water:
1.33v
2110 (12 bit resolution)
4200 (13 bit resolution)

in air:
2.6v
4095 (12 bit resolution)
8191 (13 bit resolution)

[HantraxHat]

Think I found the answer.
The ESP32-S2 ADC seems to saturate at 2.5V.
So the range that i can use is 0-2.5V with 11db of attenuation.

I tried to implement a voltage regulator a the output of the sensor with these resistor value:
R1--> 3K
R2 --> 10K

But now i have an issue that when i attach the voltage regulatore Vin (before R1) drops from 2.5V to 0.9v and the vout is 0.7V and is not what i was expecting (2.5V Vin and 1.9V Vout).

What I am missing?

Thanks