Battery voltage reading via ADC
Posted: Tue Sep 05, 2017 2:37 am
I'm seeing an interesting behavior from the ESP32 ADC when I'm trying to measure the ESP32's power supply's voltage (LiPo battery).
I have my source supplying battery connected to a voltage divider (since the board is powered by 3.3v), and that divided voltage is connected to an ADC pin.
I'm reading voltage into the pin and doubling it to get the actual voltage of the battery, however, I'm always seeing a mismatch between the actual battery voltage (as measured by a high accuracy external multimeter) and the voltage read by the ADC as seen in the table below:
The mismatch is decreased as the battery voltage decreases, I double checked the accuracy of the voltage divider resistors and they are in fact equal.
Any clue why this is happening? and how to deal with it?
I have my source supplying battery connected to a voltage divider (since the board is powered by 3.3v), and that divided voltage is connected to an ADC pin.
I'm reading voltage into the pin and doubling it to get the actual voltage of the battery, however, I'm always seeing a mismatch between the actual battery voltage (as measured by a high accuracy external multimeter) and the voltage read by the ADC as seen in the table below:
The mismatch is decreased as the battery voltage decreases, I double checked the accuracy of the voltage divider resistors and they are in fact equal.
Any clue why this is happening? and how to deal with it?