1 Megohm Potentiometers

[briholton]

Originally Posted by Al Skierkiewicz

Bjorn,
The 1M pot will give some indication of change but the input resistance of the RC and the pot value interact. The 1M may show some change but it might not be linear. (i.e. values per degreee of rotation will vary from one end of the pot to the other and may stop changing at some point) If you need linear, accurate data, stay with the 10K to 100K values.

Depends on the input impedance of what you are connecting to of course, but Al reminds me of something here - don't forget pots come in linear taper and logarithmic taper. Make sure you get the one you want, and don't buy the cheap ones, they can be really pronounced in what Al is saying above.

[FotoPlasma]

Also, at 5V, a 1megohm potentiometer is only drawing 5uA (5 millionths of an ampere), unless I'm terrible at math. From my limited knowledge of E&M, at currents that low, I would be worried about interference from other electrical components. Jumping on the bandwagon, I'd go with 100k or 10k pots to get a reliable signal.