Hello all,
I'm currently modifying my Analog Input circuit schematics to improve precision.
I'm adding after my voltage divider, an opamp as a voltage follower to ensure precise measurement. (as you might have understood, power/consumption isn't an issue here).
My question: I have 3.3V supply. Input signal can go from 0 to 24V. I plan to use 3.3V to supply Rail-to-Rail opamp (MAX 4094).
For now, I was using 1.2V ref Voltage and prescaling @ 1/3 (max IO voltage = 3.6V) with a 24V to 3.6V voltage divider. But as the max supply for OPAMP is 3.3V, I was planning to use different prescaling ratio (2/3) and adjust my voltage divider.
Now my question: Using 1.2V vref, is it better to use a 24v to 1.8v voltage divider and use 2/3 prescaling or 24v to 1.2v voltage divider and use no prescaling? Or is it strictly equivalent? Is the prescaling inducing any significant error in 10bit sampling? Sampling frequency shouldn't be an issue right?
Hope my question is clear.
Thanks in advance for you help. Regards.
Francois
