Increase potentiometer accuracy by using both dual gang

Other Hardware Sensors
1

Hi.

I just have a general questions about potentiometers and analog inputs.

I have a 10K linear slide potentiometer with 2 seperate gangs and I was wondering if I could use them seperately on 2 different pins and add up the result to get twice the resolution.

Or would I be better of to run the gangs in paralell and connect them to one pin, making it a 5k single gang potentiometer?

Or is it kind of pointless and I should just use the one gang one one pin?

thx for enlightening me!

Andreas

2

Running the two into two separate pins would add about 1 bit of resolution/accuracy, paralleling would not.
This is a case of oversampling (though not in the time domain). Note that the effect relies on the variability of the track resistance from one track to the next - if perfectly matched you'd get no benefit.

Using separate pins would allow for the possibility of marking one track as noisy and ignoring it should that
happen at some point - giving a longer time before needing to replace the slide pot.

Adding a highish value resistor between the wipers would reduce the severity of noise should one track
become scratchy, you'd not have to know which track is defective. And you'd still get the benefit of
oversampling.

Interesting question, BTW, it sounds like a good reason to use stereo linear slide pots in a digital
mixer even though a single channel is enough.

3

Thanks for the quick reply. That's very insightful. What ballpark do you mean with highish resistor?

I am thinking that the resistor gangs are likely slightly imperfect so, I shoud be getting some added accuracy.

I will definitely give it a shot.

4

The cross-link resistor should be say an order of magnitude higher than the tracks to avoid reducing the over-sampling effect, so 100k for 10k pot ought to work. Its not critical it just reduces the amplitude of noise when one wiper is travelling over insulating dirt on the track. Its a nice trick if it works, though it might be
hard to measure without a very steady hand on the slider...

5

Clever way to try to increasing resolution.
Added to my list of tricks :slight_smile:
Leo..