Hi The only place the sensor *might* be used is during holdover. There is no practical reason to use it while the TBolt is locked to GPS.
*If* it's used in holdover, it gets "trained" by watching the control voltage and the temperature while the beast is locked to GPS. That information is then used when it goes into holdover to improve time drift while in holdover. The first test would be to put one in holdover and see if the DAC voltage changes at all while it's there. If it changes, the next step would be to see if the change is simply a function of time (= aging correction). Bob -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bill Dailey Sent: Tuesday, December 11, 2012 10:45 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Thunderbolt oven / non-stable operating temperature If it is used for tempco it should affect the temp by stabilizing offset with temp changes correct? Maybe a more correct approach would be to disconnect it and test. Has been awhile since I read that testing stuff. Doc Sent from mobile On Dec 11, 2012, at 6:39 AM, "Charles P. Steinmetz" <charles_steinm...@lavabit.com> wrote: > 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 > > > > > > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
