[volt-nuts] LTZ1000 resistors, lower collector currents

[John Devereux]

Frank Stellmach <frank.stellmach at freenet.de> writes:

> John,
>
> all drift parameters of R1, R4, R5 were attenuated by the circuitry by
> a factor of 100, R2 and R3 by a factor of 300. Therefore, bulk metal
> foil is not needed, also wirewound precision resistors will do.

> Their T.C. is between < 1 - 3ppm/K, compared to (+/-1 +/-2) ppm/K of
> the S, K types, which is exactly the same.
> Even the Z202 type Vishay resistors are no better than (0.2 +/-2) ppm/K.
>
> Therefore, the contribution to T.C. for all types is about
> 0.02.. 0.03ppm/K or less. I think, that's to be neglected, as 0.1ppm/K
> total is very fine.
>
> Drift over time of ww. vs. molded metal foil is exactly the same,
> i.e. 20ppm/yr shelf life, contributing 0.2ppm/yr. max., compared to
> the 1..2ppm/ yr. typical for the LTZ @ 45°C.

> I have built my two LTZ references on wirewound resistors, afters 3
>years of nearly continous powering, I have not seen a drift bewteen
>both, against a Fluke 5442A, and a third LTZ in my 3458A in the last
>1,5 years of more than 1..2 ppm. Temperature drift effects I also could
>not distinguish from other stationary/reversible drifts.
>
> If you are living in UK (what is: 'me.uk'?) , visit
> rhopointcomponents.co.uk.
>
> They have those 0.1% wirewound resistors 'econistor 8E16/8G16' on
> stock, I have used for the LTZ
>
> They sell also those very stable metal foil resistors "FLCY" from
> japanese manufacturer alpha electronics (swallowed recently by
> Vishay), which I have used for my Hammond type reference divider,
> which is also ultra stable after years.
>
> Its a little bit more difficult to find FLCY values for R2/R3, but
> 25K/2K should do the job...
>
>
> Frank


Hi Frank,

I could not find many precision wire wound resistors when I looked, and
most of those were only 10ppm/K & >100ppm stability. Sometimes I forget
that Digikey is not the whole world.

That is an excellent link! Thank you very much. Those "econistors"
should be ideal. Yes I am in the UK. (.me.uk is a UK registry for
personal domains rather than companies).

Thanks,

John



-- 

John Devereux