potentiometer life

Archiver

I was reading the Bourns data in Digi-key about cycle of a
potentiometer.

I want to use pot to measure the postion of a shaft, only 90
degreees.

The data said 200 cycles (4%Delta TR)

does anybody have expericance with number or turns a pot can handle
before failing or being way off?

I was planing on only a few miliamps throught it so power should not
be a problem.

TIA

Dave

Archiver

AN optical device would be preferred. how ever they are more expensive.
Model RC (cars, boats, airplanes, etc.) devices use a potentiometer with
out fail for many cycles, for the feedback mechanism. Often times I've
seen a micro switch and a cam used for damper position feed back.
Usually not more than 4 absolute positions are important anyway i.e.
open -- closed -- 45 degrees and maybe one other position. Just an
idea !!


Leroy

Dave Mucha wrote:
>
> I was reading the Bourns data in Digi-key about cycle of a
> potentiometer.
>
> I want to use pot to measure the postion of a shaft, only 90
> degreees.
>
> The data said 200 cycles (4%Delta TR)
>
> does anybody have expericance with number or turns a pot can handle
> before failing or being way off?
>
> I was planing on only a few miliamps throught it so power should not
> be a problem.
>
> TIA
>
> Dave
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

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Archiver

Dave,
Consider using a single turn cermet pot as a servo pot. These devices
typically have 10 million revolution lifetimes.
http://www.spectrol.com/pdfs/357.pdf Linearity is about 2%. You can get
better grade "servo pots" from many manufacturers, but most applications
won't need anything more than these pots offer. I have several of this
vintage in installations that are 20+ years old and running fine.
Mike

At 07:59 PM 5/8/2001 +0000, you wrote:
>I was reading the Bourns data in Digi-key about cycle of a
>potentiometer.
>
>I want to use pot to measure the postion of a shaft, only 90
>degreees.
>
>The data said 200 cycles (4%Delta TR)
>
>does anybody have expericance with number or turns a pot can handle
>before failing or being way off?
>
>I was planing on only a few miliamps throught it so power should not
>be a problem.
>
>TIA
>
>Dave

_________________________________
Mike Walsh
walsh@i...