Analog to Digital Conversion

Pages
Contributors: Nate
Favorited Favorite 32

Relating ADC Value to Voltage

The ADC reports a ratiometric value. This means that the ADC assumes 5V is 1023 and anything less than 5V will be a ratio between 5V and 1023.

alt text

Analog to digital conversions are dependant on the system voltage. Because we predominantly use the 10-bit ADC of the Arduino on a 5V system, we can simplify this equation slightly:

alt text

If your system is 3.3V, you simply change 5V out with 3.3V in the equation. If your system is 3.3V and your ADC is reporting 512, what is the voltage measured? It is approximately 1.65V.

If the analog voltage is 2.12V what will the ADC report as a value?

alt text

Rearrange things a bit and we get:

alt text

alt text

Ahah! The ADC should report 434.