[ntp:questions] Can a clock drift be too big for ntpd?

Richard B. Gilbert rgilbert88 at comcast.net
Thu Oct 25 11:47:34 UTC 2007


Maarten Wiltink wrote:
> "Patrick Nolan" <pln at glast2.Stanford.EDU> wrote in message
> news:slrnfhv6ug.7qo.pln at glast2.Stanford.EDU...
> 
> 
>>[...] I'm amazed that clock radios, plugged into the 60 Hz supply,
>>aren't as good [as wrist watches].
> 
> 
> So am I. Because here at least, they keep a close eye on the number
> of zero crossings in the power plants, and make very sure that it
> comes out right at the end of the day.

I think that power companies almost everywhere count the cycles in the 
day.  Since most are interconnected, staying in phase is mandatory!  So 
there are 60*86400 or 50*86400 cycles per day but the difference between 
any two consecutive crossings is not guaranteed to be exactly 1/100 or 
1/120 of a second.  The generators slow down when the load increases or 
speed up when the load decreases!





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