[volt-nuts] Back to voltage was Re: Precision current source

[Greg Burnett]

I think, using statistical methods, you might improve your "system" 
short-term and long-term stability by tracking the mean of the outputs of 
your multiple voltage references, plotting control charts, eliminating or 
devaluing individual poor performing references in the group (as determined 
by comparison of individuals to the mean of the group), etc. But, as a 
minimum prerequisite you'd want to characterize the TC of each contributing 
reference - and then monitor and control your environmental temperature so 
as to account for it in your process. This statistical process would be 
ongoing over time, and your "system" uncertainty would be unknown until you 
had collected enough statistical data over time.

For examples, see:

The Calibration of DC Voltage Standards at NIST
See: Calibration of Working Cell Groups (pg 246)
http://www.nist.gov/customcf/get_pdf.cfm?pub_id=23594

Metrology - Measurement Assurance Program Guidelines (NASA Ref. 1364)
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19950018123_1995118123.pdf

Greg



----- Original Message ----- 
From: "Marvin E. Gozum" <marvin.gozum at jefferson.edu>
To: "Discussion of precise voltage measurement" <volt-nuts at febo.com>; 
<volt-nuts at febo.com>
Sent: Sunday, August 22, 2010 11:06 AM
Subject: [volt-nuts] Back to voltage was Re: Precision current source


Has anyone tested or have a link describing if averaging the outputs
of multiple voltage references strung together improve short and/or
long term stability?  By how much?

I've read of attempts to do this from the volt nuts archives linking
the Chinese forum, but their good work has no follow up with
stability data beyond some minutes.

http://translate.googleusercontent.com/translate_c?hl=en&sl=zh-CN&tl=en&u=http://www.hellocq.net/forum/showpost.php%3Fp%3D1616460%26postcount%3D58&rurl=translate.google.com&usg=ALkJrhg3JjvD6sPUtn3T0rQtKv3xWuC5ag

Bob Pease wrote recently ...

http://electronicdesign.com/article/pease-porridge/what_s_all_this_long_term_stability_stuff_anyhow_.aspx


 From what I peruse, Flukes multiple zener based references run
concurrently but independently, and their drift characteristics are
assigned to each reference, not linked together.

http://translate.googleusercontent.com/translate_c?hl=en&sl=zh-CN&tl=en&u=http://www.hellocq.net/forum/showpost.php%3Fp%3D1892104%26postcount%3D285&rurl=translate.google.com&usg=ALkJrhgjHbjHQWdRXogyU8Z8aKSisWIX0Q



At 01:48 PM 8/17/2010, Dick Moore wrote:

>I suspect (which means "I don't know") that trying to regulate the
>399 heaters beyond what is incorporated in their design will be
>unproductive, and that averaging the outputs of several units in
>tandem will be better. Providing some thermal isolation for the 399s
>by protecting them from stray air currents and using thin wires or
>PCB traces is a good idea.



Sincerely,



Marv Gozum
Philadelphia, PA


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