jabastien/esp32-adc-voltage-measurement

Using the ADC to measure voltage

ESP32-ADC-Voltage-Measurement

Using the ADC to measure voltage

The function that corrects for the ESP32 ADC input impedance loading of an attached voltage divder. I have estimated the ESp32 ADC input impedance to be 1.3Mohms

#define constant 5.9;

// 0-5v range example, should be a factor of 5, but loading increases it to 5.9

// defined constant 5.9 // 0-5v range

// #define constant 7.1 // 0-6v range

// #define constant 14.6 // 0-12v range

// #define constant 18.5 // 0-15v range

// #define constant 30.1 // 0-24v range

// #define constant 38.1 // 0-30v range

// #define constant 64.5 // 0-50v range

// #define constant 130.0 // 0-100v range

float readVoltage(){

float ADCvoltage = (float)analogRead(36) / 4095 * constant;

return ADCvoltage * constant; // 0-5v range }

// I cannot fully explain why as input voltage increases and effective load on the voltage divider by the ESP32 decreases that the constant offset increases, it should be the opposite!