[volt-nuts] Traveling Standards

Bob Smither smither at c-c-i.com
Fri Aug 26 06:07:55 UTC 2011

Dear All,

Thank you so much for the great responses!  You have all given me a lot
to think about.

Andreas mentioned the lm339.  One candidate I am considering is the 
lm119ah.  Of the references I have at hand (lm119a, lt1027bcn, and 
max6350cpa) the lm119a looks the most promising.  Andreas mentioned that 
humidity and stress can cause several ppm errors.  The lm119a is in a 
hermetic to-46 package in a thermal shield - so hopefully those effects 
will be minimized.  The idea that the orientation matters is a new one 
for me.  I will be sure to mark "TOP" on the final package.

Fred advised against the use of pots.  I agree.  I was thinking of just 
using the raw reference output.  For my purposes, I don't really care 
what the voltage is as long as it is stable and can withstand shipping.

Warren - I appreciate the offer of a 1n825, but the TC is too large for 
this purpose.  I also suspect it will be noisier than the lm119a.

Dick and Charles M. - thanks for offering help with this project!  I 
will contact you off list for your address when I have a traveling unit 
prepared and will welcome your measurements of it.

Charles S. - your understanding is correct - I would ship the unit to 
anyone that is willing to measure it for me.  You idea of shipping it 
powered up deserves some more thought.  One concern I had about this was 
the added weight of the batteries for shipping.  It may be an even trade 
against having a transformer / rectifier / capacitor to make the 
required power supply level.

Thanks all!  Now to do some serious design and construction.

Bob Smither
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