[volt-nuts] Low-cost voltage reference questions

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 25 Nov 2015 11:18, "Charles Steinmetz" <csteinmetz at yandex.com> wrote:
>

> I'm curious why you think the AD587/586 are better than other
hermetically packaged references with better drift and noise specifications
-- in particular,
>
> MAX6350MJA
> AD588KQ
> LTC6655CHLS8
> LTC6655BHLS8
> REF102CM
>
> (see attached table).

Your table mentions at the bottom the LTZ1000, but you don't have that
device listed in the table.  I assume that is an oversight,  but perhaps it
was intensional.

As regards humidity, I wonder if an reasonable attempt at sealing a package
combined with silica gel inside would give an internal humidity that keeps
fairly stable.

I recall seeing a mix of chemicals on eBay that were a calibration standard
for humidity.

I assume that if one got some hermetically sealed feedthrough caps, it
would not be hard to put a PCB inside a tinplate box that's soldered along
each edge to form a hermetically sealed container. Then one would have a
sealed environment. I can imagine it would be desirable to flush out all
solder fumes before making a final seal. Maybe the flux residuals that I
expect outgas over time would cause more problems than it solves.

Note that I have never worked on anything requiring such sealing,  so I
would not be surprised if someone who has worked on such products would
laugh at my suggestions!

I note that Schott appear to produce hermetically sealed enclosures.

I would have thought it practical to build electronics at home where
changes of humidity over time could be virtually eliminated. But I have no
experience in this subject.

Dave.