[sdiy] tempco resistors

[JH.]

>Absolute resistance of the temp co is not particularly important since
>you will be trimming the scale factor of the expo anyway.

Right ...

>What is probably more important is the tolerance of the TC itself.
>+/-10% is not uncommon, ie +2700 to +3300ppm/K, and this is not easily
>trimmed.

Ok ...

... but what worries me more: How linear will it be as a resistor, i.e. U(I) 
?

I know there's wire-wound tempco resistors, and the platinum temperature 
sensors,
which are a piece of metal, and thus will be linear.

But what's inside these tiny Tyco resistors? They don't write it in the data 
sheet.

JH.