[time-nuts] My Racal-Dana 1992
Charles P. Steinmetz
charles_steinmetz at lavabit.com
Mon Dec 19 18:33:10 UTC 2011
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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