Info wrote:

It would be nice if in the future you put a blank line between your reply
and what you are replying to.  That would make your post more readable.  You
even deliberately deleted blank lines I put in there for readability.

> No, I implemented the filtercap suggestion and also tried almost
> every suggestion made by Jinx so far.

I don't think Jinx suggested a R-C low pass filter, I did.  I even derived
the values and gave a long explanation, but that apparently got swallowed by
the server.

> Thats how we work here. Someone suggests can it be this or that?
> We check, and come back: No, it cant because...

But your reasons why were incorrect.

> If someone is sure he is right he explains why he is right and if
> the others cant explain why they think he is wrong his point stands.
> You call it arguee, we call it working together troubleshooting.

That's fine when you're working together like in a design review.  It's a
bit different when you're asking someone else for a favor.

>>> There probably is a magnectic coupling
>>
>> is this not a normal pot with the shaft mechanically tied to the
>> wiper?
>
> No, its no normal pot. Ive said its a special expensive one, laser
> trimmed for industrial linear measuring use.

(blank lines restored for clariy)  Yes, you said it was laser trimmed, but
this is the first time you said anything about magnetic coupling.  That
makes a huge difference.

> It has got a plastic part outside a alu.

What's a "ALU".  To me that means "arithmetic logic unit", which doesn't
apply to pots.  You say you have problems with english, so don't make things
worse by using abbreviations unless you are really really sure they will be
universally understood.

> housing that moves ontop
> of a stainless plate, no mechanical connection through to the inside
> so when the plastic part moves the wiper inside must move by mag-force
> or woodoo. (I am wildly guessing magnetic, but thats just me and I
> am barely qualified to sit on a chair so dont take my word for it)

It never occurred to you that this is really important information!!?  This
puts a totally different light on things.  My first reaction is that this is
not a appropriate pot for the job.  Of course there are going to be
overshoots depending on speed since the slider is not ridgedly coupled to
the wiper.  This also explains some of the noise.  Pots can scratch when
moving, and this wiper moves whenever there is mechanical vibration.  You
can probably even get it to resonate at the right frequency.

> These pots sits in a place that vibrates enough for them to give out
> random signals

As expected, now that you've explained the slider is magnetically coupled to
the wiper.

>> you need to explain what the real problem is.
>
> There should be no noise issues, nor jumps to begin with!

If your spec is "no" noise, then go home, quit, pack it in.  There will
always be noise.  Specifying none is useless and only undermines your
credibility.

> When I first tested the pot it was impossible to get a good reading
> due to the severe noise. Thats not normal,

It probably is for this type of pot.  I think the real problem is the wrong
pot was specified.

Step back a few layers and look at the real problem.  Apparently you want to
sense the position of something.  There are lots of ways to do that.  Slide
pots are only one, and not usually the first choice.  Look at the whole
range of possibilities, including rotary shaft encoders, rotary pots, LVDTs,
and various more "elaberate" schemes.

> Yes, its a linear slide pot. (didnt know it was called that) I
> thought you meant if it had more than one wiper inside on the plastic
> track.

I've seen pots intended for full circular position feedback that have two
wipers 180deg apart.  These pots have 4 terminals, two for the ends of the
resistor and one for each wiper.  With the right firmware you can recover
full 360deg rotational position.  I was vaguely thinking that maybe you had
one of these and connected the two wipers together.  Clearly that's not the
case though.


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