Getting an official answer from Espressif, they do plan on fixing the factory calibration in the near future I'm assuming since you get a reply in January and you are posting in February that the fix date is June 1, 2018? Thats a long time to wait for something that should have worked on day one. H...

No, as long as you don't go past the maximum of about 3.3 it will simply read max value above 1.1.

ParthRathod wrote:Hello,

ESP32 has 12bit of ADC as per datasheet. so it can measure the change of 12mV on ADC line

I am trying to read 65mV on ADC lines.but it still gives 0.
what is the minimum ADC input voltage range on ADC line of ESP32.

See the post I made right above yours. Its around 100 mv.

Hi everyone, the ADC calibration issue has actually been addressed in the esp-idf. Please see https://esp-idf.readthedocs.io/en/latest/api-reference/peripherals/adc.html#adc-calibration and https://github.com/espressif/esp-idf/tree/4048db35b6a1ac4216150480dcacdc4230f0baa2/components/esp_adc_cal . S...

Yeah i know but i wonder how is your 4-20 mA connected.. do u use external power supply? How big resistor do u use? Oh, I used a current -> voltage converter. I tried doing the resistor thing but it was too hard to get the range correctly. Something like this: https://www.ebay.com/itm/Isolation-Tra...

Hello vseven, can u please show me your code for reading the current loop? Also, if u can provide me your wiring i would be much thankful!!!! Not sure what you mean for wiring, the voltage goes to a analog input pin and the ground to a standard ground pin. As for reading its just a analogRead of th...

Yeah, thats why I used 0.2 - 1.85 for my range. For me on my chip going up to 1.85 seemed linear still. I have a bad feeling, and based on some other things I've seen, that there is a difference from chip to chip. Makes it kinda hard to mass produce something unless you arbitrarily used like 0.3 - 1...

I have a commercial grade device that reads 4 - 20ma and scaled the temp and humidity for those readings. I compared that to known good calibrated temperature and humidity sensors. Once that was calibrated I used that reading against the ESP32 reading to verify the accuracy.

Vaisala HMS82: https://store.vaisala.com/us/hms82-outd ... y/HMS82/dp

My sensors are actually 4-20ma that I'm converting already with a current -> voltage adapter. The one i have lets me change the zero and max so i have it set for what seemed to be the most linear part of the range which was 0.20v (105 on ADC) and ending at 1.85v (1980 on ADC). I then scalled my sens...