Potentiometer rotation angle?

[untune87]

Hi all, I wonder if anyone can clarify something in regards to pots both modern and vintage;

I have a couple of dial plates, typical flat round aluminium scales that will sit stationary under a knob so that the pointer will denote a value when turned. At present I have two: one is a modern Ohmite one, the other is a (seemingly) vintage Yaxley example that I recently acquired from the USA.

I was planning to use the Yaxley one for a project when I noticed that the gap between the minimum and maximum values is a little narrower than the Ohmite, despite them being the same overall diameter. This suggests that they are each designed to be used with pots that have slightly different degrees of mechanical rotation.

I'm wondering if there is any standard (or rather, if it is different now) and if perhaps certain types/constructions of pot have particular degrees of rotation. I'd like to use the Yaxley plate but it might force me to locate a specific old potentiometer in order to match the scale.

Any info is greatly appreciated!

Cheers

[Terry_VK5TM]

While it may appear that 270 deg is the standard pot rotation, you can go to places like Digikey and in their sort filters for potentiometers you can find rotation, they range from 120 to 360 deg of rotation (they actually list up to 3600 deg - not sure how that works).

So you should be able to measure the anglular range of the dial and find a modern pot to suit.

[untune87]

Ahhh thanks for that Terry; I'm trying to stick to vintage components for this one but I guess it's just pot luck (pun not intended) with those unless buying new, where you can narrow the search down like you say

Perhaps the 3600 degrees are ten turn pots!

Cheers

[kalee20]

Originally Posted by Terry_VK5TM

(they actually list up to 3600 deg - not sure how that works)

Ten-turn potentiometer perhaps, for use with dial-counter knob?

(Actual rotation likely then to be 3630 degrees).

[DMcMahon]

I assume the Digikey sort filter search just listed all pots with their rotation angles, i.e. the search was not specific to or sorted for pots suitable for dial pointer use.

David

[Radio Wrangler]

Don't believe the published numbers too much, they are usually the mechanical end-stop rotation limits. Expect an electrical dead band at either end.

David

[Craig Sawyers]

Bourns type 91 is 240 +/-5 degrees electrical angle linear and 225 +/-5 degrees audio taper in conductive plastic, and 240+/-6 electrical angle linear and 225+-6 degrees in cermet. Mechanical angle is 300+/-5 degrees

Bourns precision type 6539 is 340+3 degrees electrical angle 340 +8 -0 degrees mechanical.

I'm using both in a design, so had the datasheets to hand.

I quote them only to show that there is absolutely nothing standardized even in pots from the same manufacturer.

Craig