[volt-nuts] Low-cost voltage reference questions

Dr. David Kirkby (Kirkby Microwave Ltd) drkirkby at kirkbymicrowave.co.uk
Sun Nov 29 06:49:14 EST 2015

On 29 November 2015 at 10:53, Charles Steinmetz <csteinmetz at yandex.com>

Dave wrote:
> 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.
> That is exactly what I do.  I typically package references in small, cast
> aluminum boxes, and include as large a dessicant packet as will fit in the
> unused space.  Without any special precautions as to sealing, I have never
> seen one of the dessicant packs more than slightly used, even after a
> decade or more and even if there was a hole in the box wall to allow for a
> potentiometer adjustment.  With precautions (using a gasket or sealing the
> seam with RTV after final testing, and sealing any adjustment holes), I
> think you'd be good for a lifetime.
> Best regards,
> Charles

Are you, or anyone else, aware of any reasons silica gel should not be used
in electronic enclosures?

A friend and I were thinking of developing antennas, which would be used
outside, but enclosed in a fibreglass or similar tube.  I suggested
flushing the antenna with nitrogen, then putting silica gel inside.

He was of the opinion that silica gel was not a good idea. Instead he
reckoned on pressuring the inside with nitrogen above ambient pressure,
and having gas-tight seals would be better. I'm personally of the opinion
that's a bit over the top, as then you need valves to get the nitrogen in.
His idea stuck me as a bit of a sledgehammer to crack a walnut, but he has
better mechanical engineering skills than me.

The difference with the antennas compared to a voltage standard is antennas
would be used in a more hostile environment than a laboratory. So perhaps
whats reasonable in a lab, is not so sensible for an antenna exposed to
wind, rain, ice etc.


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