[time-nuts] My Racal-Dana 1992
ed_palmer at sasktel.net
Mon Dec 19 14:22:51 EST 2011
My restart followed the same pattern as yours. Start high, go higher,
drift down, undershoot, recover. The start was 10 MHz +51 counts, rise
to +60 counts after 5 minutes, drift down to a minimum of +8 counts
after 90 minutes and recover to +11 counts after 10 more minutes for a
total shift of -40 counts (peak error of 4e-9). I'm going to redo all
these tests, but I think I'll be sticking to the external standard.
On 12/19/2011 12:33 PM, Charles P. Steinmetz wrote:
> I wrote:
>> I put one of mine in standby earlier this afternoon. I'll turn it
>> back on tomorrow afternoon and report the results.
> (All results using 10 second gate): Yesterday, the 1992 had been
> reading "000.000000 E-3" stably for several days, and I switched it to
> standby. After 16 hours in standby, it came on 4 counts (4 mHz) high,
> rose to 9 counts high in 5 minutes, hung there for about 15 minutes,
> then slowly came down to 0 over the next hour. It undershot 0 by the
> tiniest bit (several minutes of occasionally reading "999.999999
> E-3". It has been reading 0 stably for over 3 hours now.
> So, mine also has an error with a long time constant when it comes out
> of standby, but of lesser magnitude than Ed's (peak error 9x10 E-10).
> I presume the magnitude of the error may change with ambient
> temperature (in my case, 74.1 F throughout).
> Chuck speculated several days ago that the 9462 fine adjustment may be
> an oven parameter (temperature?) adjustment. The long, oscillatory
> nature of the settling when the fine adjustment is changed does
> suggest the action of a somewhat underdamped control loop. Both the
> ringing and the long time constant tend to support the oven
> temperature hypothesis (but I am still reluctant to believe they would
> design a frequency adjustment this way).
> Best regards,
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