[time-nuts] Thunderbolt oven / non-stable operating temperature
Charles P. Steinmetz
charles_steinmetz at lavabit.com
Tue Dec 11 12:39:59 UTC 2012
Bill wrote:
>Well, perhaps you are not looking close enough. That is you need to
>be observing
>at a finer level of comparison. The changes, observed here and at another
>location, are in parts in 10-10 to 10-11 range, sometimes
>larger. At one of the
>locations there was a direct correlation to the air conditioning cycle.
It is not clear what part of my message you are referring to.
My main point was that the information from the DS1620 temperature
sensor does not appear to be used internally by the Tbolt. In my
observation, subjecting the sensor alone (thermally isolated from the
rest of the Tbolt) to wide temperature swings (-10 to +120 C) did not
produce any observabe effect on the operation of the Tbolt. If the
temp sensor data were used internally by the Tbolt, one would expect
a significant effect from such a wide swing -- one that couldn't be
missed. If that large and fast a reported temperature swing produced
effects only at the e-10 or 11 level, I would attribute it to
imperfect thermal isolation of the Tbolt from the temperature
stimulus (i.e., stimulus affecting the oven temperature or EFC
circuitry of the Tbolt), not as the Tbolt's response to the
temperature change reported by the DS1620 sensor.
If you were referring to my side point -- that allowing slow changes
to the Tbolt housing temperature does not appear to be materially
different from regulating the housing temperature -- my observations
were that this was true down to at least 5e-13. Of course, there are
two variables -- total swing and rate of change. By "slow," I mean a
rate of change of 0.25C per hour or less [DS1620 reported
temperature]. My diurnal swings are no more than 2C per day and
usually less [DS1620 reported temperature] (they can be as much as 5
or 6C seasonally, but those changes happen over weeks). A/C cycling
likely subjects the Tbolt to a significantly greater rate of change
than what I mean by "slow," even if basic precautions are taken
(e.g., putting it in a cardboard box).
Best regards,
Charles
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