[sdiy] Pots, cermet vs conductive plastic

[Mattias Rickardsson]

At 06:17 2005-10-03, Paul Schreiber wrote:

>I am a firm believer of "you get what you pay for".
>[...]
>However, for the VCOs I wanted cermet pots for minimal drifting 
>(even though used ratiometrically cermet drifts 100X less than 
>carbon) and wanted conductive plastic (super long life) for the others.

So, a cermet pot changes its total resistance less than a conductive 
plastic pot when the temperature changes.

But if you connect it (ratiometrically) between two known voltages 
and just pick out a voltage in between, is there any difference 
between cermet and CP?
(In other words; is there really a need for cermet in VCO tuning dials?)

Other potential (sic!) differences:
The 'feel' when turning  -  does the material matter?
The 'precision', when it comes to setting the pot to 'any position'?
The 'mechanical drift'  -  does the wiper stay in the exact same place?
After a long time of no use  -  is one of them less scratchy?


/mr