The L & N 40xx
series (4040-B=10K) has a tolerance of 0.001%, 10 times better,
but usually much more expensive <?
>
It depends on what level of accuracy you need.? If 0.01% is
sufficient, you can get by much cheaper buying precision wirewound
resistors rather than a packaged standard.? For example, a set of
five 5K 0.01% resistors could produce multiple resistor values.
?
5 in parallel = 1K, 2 in series = 10K. etc.
The seller, morrex, Spare Z Electronics,?? has other values
available in his store. Two of his 5 piece sets of 1K resistors in
series would give 1K steps from 1K to 10K.
John? KK6IL
On 12/19/2022 11:45 AM, Radu Bogdan
Dicher wrote:
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Some thoughts on something like this:???
I'm wondering how well these would stack up
against something like Leeds and Northrup references.
Hello
Pete,
The "Reichsanstalt" type resistors require a heated oil
bath, and you know, how tedious this is to maintain.
The SR104 as well as the Fluke 720A first decade resistors
also have an oil bath, and you as well know, how critical
the design of such a sealed assembly is.
The thermometer inside the aluminum block in combination
with a quite small and repeatable R(T) curve makes a
cumbersome oil bath, as well as a temperature stabilization
unnecessary.
In other words: The aluminum mass replaces the stabilization
effect of the oil, and the in situ measurement of the
temperature replaces the temperature stabilization
completely.? ??
For measuring and comparing my 7 resistance standards (5 x
VHP202Z, 10k; 1x VHP202, 1k; 1 x Fluke 5450A, 10k), I use a
program which directly calculates all required resistance
values, see screen shot from my old Turbo Pascal program.
2nd column shows the temperature as measured by a 34401A,
3rd column is the actual resistance as measured by the 3458A
(afterwards, a calibration factor is applied), and the 4th
column is the calculated nominal R25 value, from its
previously determined T.C. Please take notice of the very
low StD value!
The 5450A is always used at a constant room temperature, 22
+/- 1¡ãC over the whole year (no active Air Condition used!),
and its calculated max. compensated T.C. of about 0.1ppm/K
for the 10k resistor chain, similar to the 742A's,
eliminates further corrections.
A regulated oil bath is over engineering in my opinion.
Frank?
John Kolb