Should I Use an Opamp for Low Frequencies

[fourfathom]

Applying the same voltage to the "top" of the potentiometer and the "ref" of the ADC is a common way to make a ratiometric measurement, which does not rely (much) on the stability of the reference voltage.

Agree, and I did mention this technique up-thread.  I'm curious to learn what the actual circuit looks like.

[Bassman59]

Applying the same voltage to the "top" of the potentiometer and the "ref" of the ADC is a common way to make a ratiometric measurement, which does not rely (much) on the stability of the reference voltage.

Funny, I just designed a thing that reads a bunch of pots and that's exactly what I did.

[aw_rw1]

With a 10 or 12 bits ADC and a 2-3 V FS range there is no need to worry about the amplifier.

I was thinking this too.

The voltage that you want to measure comes from the wiper of a potentiometer.  What is the source of the voltage that is connected to the top of the pot?

I used a Sorensen lab power supply. Then I started using batteries. The battery's voltages were clean when I read voltages from the stack. Though the voltages off a POT were noisy. So what could I do about this? I am seeing numbers between 670-685 out of 1023. Average of ten of these numbers is 676.92.

You may want to look at a ratiometric design.

Interesting, I may do this.

[aw_rw1]

So what could I do about this?

I looked at some voltages around the system with the ADC. Then I put back the wiper on the ADC. The noise went away. So the noise most had been a contact issue.
 

[aw_rw1]

So the noise most had been a contact issue.

Actually, the noise was coming from my laptop's charger. I plugged my charger. Then the noise came back.