[time-nuts] My Racal-Dana 1992

Ed Palmer ed_palmer at sasktel.net
Mon Dec 19 14:22:51 EST 2011


Charles,

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.

Ed

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,
>
> Charles
>
>




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