"Richard B. Gilbert" <[EMAIL PROTECTED]> writes: >David Woolley wrote: >> Richard B. Gilbert wrote: >> >>> To turn your equipment on after months of downtime and expect it to >>> lock on to the correct time with millisecond accuracy within seconds >>> is asking for a hell of a lot. >> >> Not really. He's starting a GPS receiver at the same time and that has >> to lock to 50ns. >> >> Doing it on a general purpose computer is more difficult, but not >> particularly impossible.
>Even with GPS and a full four satellite fix, ten seconds to synchronize >is extremely ambitious!! You can set the time to within whatever >precision the hardware and software support but that is only half the >problem. You also need to set the correct clock frequency. On a cold >start, the clock frequency is a moving target as the hardware warms up. With a minpoll of 4, just setting the phase correctly with zero drift compensation would at worst be out by 1ms by the next reading. And you can get a pretty good estimate of the drift, even if it is changing. The temp coefficient is not 10PPM/degree C. More like 1 or less. That means the first few measurements gives a pretty good estimate of the drift ( ie to a few PPM) and then the finer corrections can come while things settle down. >I would expect to wait at least thirty minutes for the system to >stabilize with both the correct phase (time) and frequency. _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
