Maybe you may want to test:
esp32.com/viewtopic.php?f=19&t=2881&start=30
Posted: Sat Aug 10, 2019 12:30 pm
You may calibrate your own ESP32( the nonlinear 11DB curve) with this program.<br>
All you need is a wire from pin 25 to pin 35 and a normal voltmeter.<br>
Calibration is done automatically.<br>
It produces a LookUpTable[4096] to correct your values like: <br>
CalibratedValue = LookUpTable[Read Value];<br>
I do NOT use a fitted curve but a real LookUpTable with 4096 values !
I get correct values +/- 0.01V compared to the voltmeter.