Marek Nowak

Measuring three phase using ADC

Discussion created by Marek Nowak on Jan 5, 2018

Hello everyone, I have a problem with measuring ADC.


I am building a  device with the ESP8266 + STM8S003F3P6 module which will have 3x230V network voltage measurement and transmission results + device control.

Generally, I managed to start everything, but I have a problem with the measurement of 230V mains voltage.


On the attached diagram I presented three input circuits - on each of them I can not correctly measure voltages - during debugging the adc reading jumps all the time from 0 to 1023 (max), and in general I can not get anything meaningful. I do read the adc by scanning all inputs (Scan mode), and it's probably ok here, because the signal from the potentiometer reads perfectly.

The best effects I had using the system 1 - but the voltage ratio is not linear - is it possible for a diode? Perhaps the problem is the power supply? Perhaps it would be necessary to combine the mass with a neutral conductor?


I would ask for help when it comes to electronics I am a beginner, and this measurement adc blocks me.

I will just add that I have very little space there + the system is to be cheap - there is no possibility to use operational amplifiers or separating transformers.

I would ask for help, because I can not advise myself.