Thread: Fluctuating Input Values

Hi all,

I am having trouble understanding where my issue is coming from.

Basically I am measuring the voltage of my cars two batteries.
I have setup a voltage divider for each with a 330ohm and 100ohm resistor.

This gives an output of 2.91v when the battery is ~12.46
for each the scaling factors are
1. 0.2341920
2. 0.2325581

But the raw input values seem to fluctuate anywhere from 480 to 780 randomly even though the input voltage has not changed. I can stick the multimeter across the end and get a constant 2.67-2.68V stable, yet the display is showing anywhere from 1.76V to 3.8V

I have tried multiple ports and this still seems to happen on every one. Even if I change the resistance to give a smaller value it is still happening.
I am also running two temp sensors and these appear to be working well with stable values.

What am I doing wrong or what can I try next??

thanks
Thwack