In case you missed the significance of Tom's clarification below, note
that the thermal conductivity of helium is 6 times that of air and the
heat capacity of helium is 5 times that of air. These are big differences!
We once built a GCMS for NASA; two were landed on Mars. Modules of the
GCMS were heated to 225° C in operation by various foil and wire wound
heaters. Tested in one atmosphere of air or in 25 millibar CO2 (Mars
atmosphere), these heaters worked well. At one point during organic
cleaning, I happened to run the heaters in helium at slightly lower than
atmospheric pressure; the heaters could not be heated to 225° C because
of the characteristics of helium.
Helium has unusual properties!
Larry
On 3/12/2016 3:03 AM, Tom Van Baak wrote:
Neville,
Apparently it's not vacuum mounted, but helium filled. Lots of good info here:
http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1965-03.pdf
/tvb
----- Original Message -----
From: "Neville Michie" <[email protected]>
To: "Discussion of precise time and frequency measurement" <[email protected]>
Sent: Saturday, March 12, 2016 2:19 AM
Subject: Re: [time-nuts] quartz thermometers
It always puzzled me that quartz crystals would be considered prime temperature
sensors.
I can see that an instrument could be built that reliably showed many decimal
places of reading,
but I could never accept that a vacuum mounted quartz crystal would be closely
enough
thermally coupled to whatever was having its temperature measured.
...
--
Best wishes,
Larry McDavid W6FUB
Anaheim, California (SE of Los Angeles, near Disneyland)
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