SR104 long term drift

[JFP]

Hello,
Does anybody get experience about the long term drift/stability of a 10 K SR104 standard resistor ? Does 0.8 ppm after 40 years (yes fourty) appear usual ? Thank you.

[Conman]

After 40 years of service I think the old girl is tired. ESI states stability as +/- 0.5 ppm/yr typical.

[Bryan]

Is that 40 years ago to today or in the last year.
I have one on hand that measured 9,999.9837 in May 93 and April this year is 9,999.9898.
It has had a fairly linear increase up to 2013 at peaking at 9,999.9900.  I figure I'm at 0.63ppm after 23 years.

[JFP]

It is 40 years ago (-0.6 ppm in 1976 on the factory calibration chart in the cover) to today.

[OlDave]

Don't forget to factor in the redefinition of the ohm and volt in 1990.

"The U.S. representation of the ohm based on the quantum Hall effect to be maintained at NIST starting January 1, 1990, using the internationally agreed-upon or conventional value of the von Klitzing constant R_K-90 = 25 512.807 Ω exactly. From quantized Hall resistance measurements it is calculated that Ω(NIST-90) will exceed Ω(NBS-48)_01/01/90 by 1.69 ppm."

The full document can be found at
http://www.nist.gov/calibrations/upload/tn1263.pdf

[DiligentMinds.com]

You wouldn't think so, but it happens-- the TCR curve [alpha and beta] of your SR-104 will change slightly over long time periods, and will have to be re-measured every few years.  (I was told this is due to the smaller wire size used as opposed to some other standards-- but who knows why really).  Fortunately, if you have another stable 10K [like another SR-104], you can do this yourself with just a 3458A, a reversible low-noise 1mA current source [or reversible 20V low noise source], and two temperature controlled cabinets.  This will take a long time, so it will need to be automated.

I have two SR-104's that seem to be drifting in an almost linear fashion at about +0.07ppm/a ...  I would be interested to know how others' SR-104's are doing...

-Ken