[sdiy] Pots, cermet vs conductive plastic

[Mattias Rickardsson]

On 23/04/2008, JH. <jhaible at debitel.net> wrote:
> >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?
>
> Depends on the load, i.e. on the resistor value from the pot's wiper to the
>  virtual GND summing node, compared to the pot's own value.
>  The pot and the resistor will not have the same tempco, so there will be
>  some temperature drift. High value for resitor and low value for pot will
>  reduce this effect.

Yes, but if the load is neglected... if you really just pick out a voltage...
A potentiometer is never perfect in the way its resistance varies over
the shaft angles, for example. Is there anything that could result in
temperature differences?


/mr