AVR-Chat

Hi all,

 

I have an ATMEGA32 and I am using the ADC to measure the power supply that
is connected to the device.

 

Having done a similar thing with other processors, I am stumped by what I am
seeing with the AVR device.

 

I have a potential divider on the input so that I can measure up to +32V

 

I have a 10K resistor to ground with a 56K resistor in series with the +
supply I want to monitor. The ADC in the datasheet suggest an input
resistance of 10K is the ideal load.

 

When I measure and do a calibration of the ADC at +24V I get a good reading.
I now set the supply to +12 and I get a reading of +1V above this.

 

I am busy taking readings to see if the readings are linear.

 

The ADC ref is a nice clean +5V from the supply (I am assuming ratiometric
on my design)

 

 

Has anyone any clues to why I am seeing this from the ADC?

 

Cheers

Dave.

 

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Very funny Scotty, now beam down my clothes.

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