[volt-nuts] Vishay Z-foil

[Frank Stellmach]

Hello Andreas,

I ordered from Teltow, and got very good support from them, and 
especially from the Field Design Engineer of Vishay PG Heilbronn, who 
gave me additionally many useful hints and a fruitful discussion.

He could not give me a hint, how to get such "typical" / perfect parts 
from Z-foil resistors, as those obviously can not be produced on order.
Instead, a combination of a C- and a K foil resistor is recommended, 
i.e. VHP 101/103, which give +/- 10 ppm over 15..45°C, i.e. these 
resistors really are defined by a box method specification. But thats 
also not better than 0.3ppm/K.

Well, the specifications and all the publications around the Vishay 
Z-foils in fact do not use the box method of specification.
Especially the R over T diagram implies a differential TCR, although, it 
is in fact "usual" to use the chord slope specification, and this is 
explained only in some other publications, search for my citation.

I wanted to build something stable like the SR104 on lower budget and 
much more simple, but the Z-foil resistors won't do the job.
That's a pity.

Anyhow, I will get a feedback, what happened to the rest of the batch.
A total of 27 VHP202  resistors were produced and measured, just to 
fulfill my order...

Frank