Perhaps there is nothing wrong with the integrator. The control voltage is brought out to a jack. Granted you have nothing that can measure volts to 10E-12 or 13, but do you see a change in voltage when you switch from 100 seconds to 1 second time constant? You should wait ten time constants or more after switching. Wait, that's just a rule of thumb. How many time constants do you have to wait to get a time constant delta below 10E-13? My Burrington's tables don't go to that accuracy.
Perhaps the 1 second time constant is required for tight control. Bill Hawkins -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of John Ackermann N8UR Sent: Tuesday, April 05, 2005 8:53 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] 5061 Cs frequency shift with long time constant? This is very odd (I seem to be collecting these sorts of problems) and I wonder if anyone else has seen something similar. I got my 5061A trimmed to the point where a 5 day run against GPS showed an offset of less than 1x10e-13. I then switched the unit into the long time constant mode and now see that the offset (over 36 hours) is -1.7x10e-12. Nothing else in the setup has changed. It's hard for me to see how simply changing the loop time constant would change the frequency of the standard, especially by this much, but stranger things have happened. Has anyone else experienced a shift like this when switching the time constant? Thanks, John PS -- I was able to partially, but not completely, reproduce the phase shift that I wrote about a couple of weeks ago by jiggling the 1 PPS cable to the counter. Replacing that cable seems to have resolved that problem. _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
