There are at least two concerns.
When using a potentiometer as a voltage divider, any potentiometer will do since it is just the ratio i.e. whether 10k or 100k or 1Meg. What I want to know is are there any factor we should decide on when choosing either 10k,100k or whatever.
One more--well, actually two: certain values are more robust than others. For example, a wirewound potentiometer that's wound with very fine wire may wear the wire out after fewer revolutions than you'd like. But one that's wound with coarse wire has lower resolution (if it's otherwise the same), so that's another consideration. Also, I think you'll find quite a bit of variability in quality according to how one is built, but also expect very high values to not survive as well, as a rule, as lower values in the same product line.
Cheers, Tom
The resistance can affect a couple of things. Let's say you are feeding an analog to digital converter and the pots are fed from the reference voltage. The higher the resistance, the less current drawn from the reference. Some references won't supply a lot a current - a few dozen mA for example. In this case a 20 K pot will be helpful because it will draw so little current that it won't be a serious loading factor on the reference (i.e. 4.096.v/20K = .2mA).
However, the Zout of the 20 K pot is less than 1 Ohm to about 1/4 the max. value, or 5 K (Using a Thevin equiv. circuit). 5 K may be too large to drive an ADC with a fast aperture (sample) time. This is because there is an RC time constant created by the pot and the sample capacitor in the ADC. You would need to drive the ADC with an op-amp to use this high of value.
Hope this helps guide you.
Dave,
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