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Topic: Uno Reference Voltage of 1.1v (Read 3 times) previous topic - next topic

Coding Badly

Its not a stabilised voltage referance.


You are not reading the specifications correctly.  The variation is due to manufacturing differences.

retrolefty


Its important to read the spec sheet for the Atmega328 when looking at the internal voltage referance specs.
The 1.1 volt referance can vary anywhere between 1.0 to 1.2 volts, which is 20% variation.
Its not a stabilised voltage referance.
If you want a stabilised referance voltage for things like calibrating voltmeters, then you need something like this.
http://www.analog.com/en/special-linear-functions/voltage-references/adr4525/products/product.html
Voltage guaranteed to be stable within 0.02%.
They aint cheap though.




I'm not sure I can agree with you that the internal voltage reference is not a stabilized voltage reference. There can be device to device variation for the nominal 1.1vdc band-gap reference, but for any specific chip it will be a stable voltage reference that will be somewhere within that stated range. And once one does actually measure the specific bandgap voltage of their specific chip then steps can be developed a calibration factor one might apply to ADC readings.


Lefty

Coding Badly

...hook up the Positive of my battery power source to A1, read the value, and get 97.36363636363636% of that value as the current voltage in my battery source?


Your "battery power source" has a voltage less than 1.071?

gggggggg


...hook up the Positive of my battery power source to A1, read the value, and get 97.36363636363636% of that value as the current voltage in my battery source?


Your "battery power source" has a voltage less than 1.071?


No my source is ~5v.   My reference voltage is 1.071v

mauried

The spec sheet is here.
http://www.atmel.com/Images/doc8161.pdf

Sect 28.8 ADC Characteristics.

Vint Internal Voltage Ref   Min 1.0 Typical 1.1 Max 1.2
Seems pretty clear to me.

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