[volt-nuts] Vishay Z-foil
frank.stellmach at freenet.de
Sun Nov 20 22:33:32 UTC 2011
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...
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