This seems to be turning into a rabbit hole from which there can be no possible
return. With no evidence, you question my competence and cast aspersions on my
testing methodology. I give up.
Have a nice day.
Bob -----------------------------------------------------------------
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
From: Azelio Boriani <[email protected]>
To: Discussion of precise time and frequency measurement <[email protected]>
Sent: Saturday, November 5, 2016 7:02 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
...with a 20bit DAC, a suitable voltage reference for that DAC and an HP3458...
On Sun, Nov 6, 2016 at 12:39 AM, Bob Stewart <[email protected]> wrote:
> Hi Hal,
>
> With a 20 bit DAC, even a small aging rate is going to show up. I'll let the
> one GPSDO cook for a month or so and see what it shows then. I'll also pull
> the data from the log file and see if I can see any correlation between the
> temperature and the EFC over time. IOW, for data points separated by 3.5
> days, does the temperature difference between the two point seem to play a
> large part of the change in the recorded DAC value.
>
> The graph was made from the logging data sent to the PC. But, the firmware
> doesn't have access to historical data on the PC, so something is needed for
> aging calculations. Tom mentioned here recently about the 58503A GPSDO
> saving 64 hours of data for it's aging calculations. So, I just added a few
> hours to that to get to 3.5 days of history in the GPSDO.
> Bob -----------------------------------------------------------------
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
> From: Hal Murray <[email protected]>
> To: Bob Stewart <[email protected]>
> Cc: Hal Murray <[email protected]>
> Sent: Saturday, November 5, 2016 6:23 PM
> Subject: Re: [time-nuts] Thermal impact on OCXO
>
>> The OCXO has been hot for a number of months.
>
> Then I don't understand why it is still aging that much.
>
>
>> I changed the firmware to save the DAC voltage every 30 minutes for 3.5
>> day
>
> That's not very long.
>
> How did you make the graph? You had to get the data out to a place where you
> can plot it somehow. If you can do that, why are you "saving" the data? I
> assume you have a serial port to a PC or something like that.
>
>
>> The fuzz in the temperature line is, indeed, the HVAC cycling
>
> You could try putting a box over the unit to see if that slows down the
> temperature changes.
>
> Mostly, you are trying to block air flow.
>
>
>
> --
> These are my opinions. I hate spam.
>
>
>
>
>
>
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