LTZ1000 resistors, lower collector currents
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
me.uk ist gleich als z.b. mich.de
Dave
-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On Behalf Of Frank Stellmach
Sent: 07 November 2011 20:06
To: volt-nuts@febo.com
Subject: [volt-nuts] LTZ1000 resistors, lower collector currents
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
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Frank Stellmach frank.stellmach@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