[volt-nuts] Traveling Standards

shalimr9 at gmail.com shalimr9 at gmail.com
Thu Sep 1 14:21:33 UTC 2011


About the traveling standard, I'll be glad to have it checked at my day job. We have our own cal lab and everything is calibrated NIST traceable. Not sure exactly what they have, it is a very well equipped lab. I know they have at least one HP 3458A and a Fluke 5500A calibrator.

I had my HP 3478 calibrated there. It was an eBay special with a 5 years old cal sticker, and it was still well within spec with a wide margin.

Didier KO4BB

Sent from my BlackBerry Wireless thingy while I do other things...

-----Original Message-----
From: Stan Katz <stan.katz.hk at gmail.com>
Sender: volt-nuts-bounces at febo.com
Date: Thu, 1 Sep 2011 01:45:19 
To: Discussion of precise voltage measurement<volt-nuts at febo.com>
Reply-To: Discussion of precise voltage measurement <volt-nuts at febo.com>
Subject: Re: [volt-nuts] Traveling Standards

Bob,

You've heard from the experts now here's some thoughts from a mere hobbyist.

First, there was discussion, on this list, in Nov. 2008 on this issue. I
would also be happy to be able to rotate a homebuilt transfer standard
through a kind hearted soul's home lab ( don't worry Charlie, I don't intend
to piggyback on your good hearted offer to Bob) equipped with 732A's and
access to an employer's NIST traceable lab gear. In fact, a master
metrologist did take pity on me, and actually gave away a little standard
which I had to use as soon as I got it at exactly 63.5F to perform the
transfer.  That little standard "moved away"  300ppm in 90 days from the HP
3456 and ancient HP735A transfer standard I applied it to (the 3456 and 735A
were only about 30ppm apart by then). Take a look at the Nov 2008 archive.
Some were happy with the cost/performance of the Geller product
http://www.gellerlabs.com/SVR%20Series.htm, Some others considered its long
term stability suspect. If that's the case, in time, you'll just have
another suspect clock in your collection. As my knowledge, and appetite for
metrological perfection falls quite short in comparison to the scholars and
master designers who dominate this list, a 10ppm transfer capability, from a
transfer standard with a long term drift of less than 5ppm/year would be a
joy. In that regard, my own preference would be to build the clone of the HP
3458A reference board described by Max Carter
http://www.maxmcarter.com/vref/. The use of metal film resistors on the
board as shown I will generously presume to have been placed there after the
builder ran out of funds for Vishay wirewounds, or thin films. In any event,
I can't afford precision, low tempco resistors either. I would also use
metal films, but I would ovenize as per your off-the-cuff, and HOPE the heat
blows off the humidity. I would build an aluminum plate "coffin" around all
components except the LTZ1000 (is it also position sensitive like LM399s?),
build a precision heater control circuit to heat either resistor arrays or
pilot lamps sprinkled around the board, fill the "coffin" with insulating
foam, and seal. Maybe this arrangement would have better long term stability
than the Geller, or maybe it's DOA. Comments from scholars and master
designers welcome. I realize, with the whole board ovenized, shipping under
battery power may be a bit impractical.

As far as relying on the kindness of strangers, that's ok for a one off.  To
regularly (e.g. yearly) calibrate whatever homebuilt transfer standard you
come up with, is a different matter. I realize the list members with the
highest level of standards control, are also the same ones immersed in
highly complex lab project on their own precious time. They can't be
expected to waste time tearing open scores of packages, and then repackaging
standards for return. May I ask if there's someone on this list who has a
wife, child, nephew, niece, or cousin, willing to run a small business from
dad's/grandpa's home lab? While Geller charges $10.00 to recalibrate your
Geller "transfer reference" by throwing it across an HP3458A, a volt-nut
Grandpa Lab may just be OCD enough to demand to have the little family
business do a right and proper transfer right from grandpa's bank of 732A's.
In which case, you aren't going to get away with $10.00 cal+ship. Grandpa's
lab would have to charge at least $50.00. I would certainly be willing to
pay $50.00 vs. $500 to a commercial lab. What a bargain!

Regards,
Stan



On Thu, Aug 25, 2011 at 1:14 PM, Bob Smither <smither at c-c-i.com> wrote:

> Fellow voltage aficionados ,
>
> If this has already been discussed - my apologies.  I could not find this
> topic in the past several months of list archives.
>
> Like many of us, I have an ever growing collection of voltmeters and
> related instruments.  Like the man with two clocks who is never sure of the
> time, I now have enough volt meters to have doubts about all of them.
>
> So - I was wondering if those on this list with really good voltage
> measurement capabilities would be willing to help those of us without.
>
> What I have in mind is creating a small voltage reference circuit based on
> one of the many available IC references that is stable enough in both time
> and temperature to use as a transfer standard.  I am thinking that the
> actual voltage is not important, just the stability.  Using the ICs that I
> am familiar with the actual reference voltage would be around 5, 7, or 10
> volts.  Said reference would be mailed to a willing list member who would
> record his reading of the reference and mail it back.
>
> I don't have such a reference yet, but have breadboarded a couple and the
> idea seems like it might work.
>
> My first objective would be to obtain a reference that I could use to get
> all my meters to agree.  Since the best meters I have are an HP3455A (best
> accuracy about 20 - 40 ppm, and only for 24 hours) and an ancient (but very
> usable) Fluke 883AB (best accuracy is 100ppm), I would be very happy to have
> a reference that I could trust to 10ppm.
>
> So - two questions for the list:
>
> 1.  Does this sound feasible?  Am I overlooking anything that would keep me
> from being able to transfer a 10ppm known reference?
>
> 2.  Any list members that would be willing to help with this?  I envision
> mailing a small package with the reference in it along with an enclosed,
> postage paid, return box.  I am asking for a member that would take the
> reference, apply power, let it warm up, record the room temperature and the
> reference voltage to within 10ppm, and return it to me.  If you prefer to
> respond off-list - smither at c-c-i.com.
>
> BTW - I live in Friendswood, Texas (near Houston).  Any fellow nutters
> close enough that I could hand deliver the reference?
>
> Best regards,
>
> Bob Smither
>
>
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