Difference between Pots

[Overclocked]

What is the difference between A Single Turn Cermet Pot, a 10 Turn pot, a 20 Turn pot and a panel mount Linear Pot? Are they more precise than a Linear Pot? Will single turn or multi-turn pots give better resolution than a linear pot? Ive noticed that the Single and Multi-Turn Pots have a tolerance of +/- 10%, while a Linear pot has a tolerance of +/- 30%, is this the only advantage they have over panel mount linear pots?

 

[kchriste]

Are they more precise than a Linear Pot? Will single turn or multi-turn pots give better resolution than a linear pot?

You can't really say that. A linear taper pot can be either a single turn or multi-turn pot. They can be precision pots, or not, whether they are linear, log, multi or single turn. You're unlikely find a logarithmic taper pot in the multi-turn format, but there is nothing saying it couldn't be done.
The tolerances you quoted probably have more to do with the total resistance value of the pot rather than it's linearity:
You could have a pot with a resistive tolerance of 5% with a linearity tolerance of 1%.

 

[Boncuk]

Hi overclocked,

just to comlete the answers of your questions: A 1-turn (actually not one turn, about 300degrees) covers the entire span within those limits. A 10, 20 or 25-turn pot uses a worm gear to drive the center tap, hence it takes the respective number of full turns to cover the entire range.

With a worm gear type pot adjustments can be made more precisely. One further advantage: Multiturn pots maintain their position unless the worm is turned by heavy vibration or earthquakes.

Boncuk

 

[crutschow]

Generally you don't care that much about the accuracy or linearity of a pot since, in most applications, you just adjust the pot until you get a desired output. The advantage of a multiturn pot is that it gives finer adjustment (precision) of the setting.

An exception to this are large multiturn (typically 10) instrument panel pots which have a high accuracy and linearity, with the ratio output precisely related to the turns position (for example 7.0 turns would give an output at the wiper of 7.0V with 10V across the pot).

 

[eblc1388]

One further advantage: Multiturn pots maintain their position unless the worm is turned by heavy vibration or earthquakes.

Boncuk

Of the multi-turn POTs I know, they are all but a "long" linear pot. The insulation body on which the resistive element(wire) is wound is bent into a helix so that it can fit into a normal shape housing. When user turns the tap, the tap just follows the helix making contact with the resistive element giving minimum to maximum resistance.

No worm gear is involved.

You have mistaken it with the "fine tune" attachment which is used to provide "multi-turns" fine adjustment to something that cannot make multiple turns like a large air variable capacitor.

 

[Overclocked]

Cool, thanks for the clarification. But which one would be better to allow a finer (or more resolution) adjustment for a power supply? Does it depend on value of the feedback resistors? For example, Ive replaced a 10k pot with a 2k Pot and noticed Ive gotten a lot more "resolution" than a 10k pot, since a 10k Pot tends to be a bit jumpy and sensitive. But would I get better resolution if I reduced the 2k pot to 1k?

FYI, The Other resistor in the feedback section is 1k.

 

[kchriste]

Reducing the resistance of the POT will give you finer adjustment resolution at the expense of less adjustment range. It is a compromise. If you what more range and easy adjustment, then a multi-turn POT is the answer.
Post a diagram of the circuit and the voltage range requirements, and we can give you a more specific answer.