[volt-nuts] Traveling Standards

Demian Martin demianm_1 at yahoo.com
Wed Aug 31 01:58:26 UTC 2011

To make a real PPM standard has so many technique pitfalls that it may be a
really frustrating experience. The late Jim Willians wrote something about
this in a article on checking precision DAC's. Even with the best stuff a
real climate controlled environment is more than most of us are able to do.
If you look at the manuals and construction efforts for these things there
is a lot of experience in details that's hard to just copy. Even the circuit
layouts and managing the thermocouples in all the connections is not
trivial. Here is a good starting point for understanding it:

Here is an alternate offer I'll make. I just checked and I have 3 Fluke
731b's that I'll be happy to provide for travelling standards. They are
doing nothing but occupying space on a shelf for now. I also have a 732A, a
Prema DVM and a Fluke 8506a, all of which use LTZ1000 references. Those
three have tracked each other within 50 ppm for the last 5 years without
attention. Probably none have been calibrated in the 21'st century and only
the Flukes have a common origin. Prema makes their own JJ standards. I'll
fire up the 3 731b's and check them against the trio to get things started.
I'll get them boxed in a nice reusable shipping case if you will pick up the
shipping to start this off. They may need service (the batteries are
probably shot by now), I'll leave that to you. I don't have time for more
with my "day" job.

If this is interesting send me a note directly and I'll get it started.

Date: Mon, 29 Aug 2011 22:52:24 -0500
From: Bob Smither <smither at c-c-i.com>
To: Discussion of precise voltage measurement <volt-nuts at febo.com>
Subject: Re: [volt-nuts] Traveling Standards
Message-ID: <4E5C5E78.6020109 at c-c-i.com>
Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"

Fellow Voltage Fans,

To review - I would like to have a lab standard here that I can trust to 
10 ppm or better to use to calibrate my expanding collection of 
voltmeters.  I have proposed to built a portable standard that I will 
ship to participating volt nuts on this list who will record their 
readings of the standard and share those readings with the list.

I have designed a Traveling Standard that incorporates two references 
(an LM199AH and a MAX6350E) along with an LM34 to measure the 
temperature of the MAX6350 (the LM34 is glued to the top of the MAX6350.

The schematic is attached to this page:


Following suggestions on this list (thanks!) I will use an external 
"wall wart" supply for the input 24 Volts.  This reduces any shift 
caused by the line regulation of the three terminal regulator.

My design notes are included on the above page.

I have constructed a bread board of the circuit on a plugboard.  I will 
move the circuit to a printed circuit version after some testing.

Some preliminary readings from the breadboard of the LM199AH part are 
noted on this page:


Note that these readings are taken with an HP3455A which has not been 
calibrated since I bought it new.  I would expect the accuracy to be no 
better than .01% and may be much worse.

My plan is to mount the printed circuit board version in a short length 
of 2" PVC pipe with connectors for the three outputs.

After the printed circuit board version is aged some it will be ready to 

Are there any more on the list that would be willing to make a 
measurement of the Traveling Standard?

I will collect the readings that we collectively get on the TS and make 
them available to the list.  I anticipate that with some experience we 
can all benefit from having this TS well aged and with a well known 
output voltage.

I will handle the shipping - all I ask is that you take careful 
measurements and provide them to me, then return the unit.



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