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From: ossmann@hp-and.HP.COM (Bill Ossmann)
Newsgroups: sci.electronics
Subject: Re: Getting timing from line cycles (was Re: Sidereal Time Clock)
Message-ID: <13650001@hp-and.HP.COM>
Date: 8 Jan 91 18:11:07 GMT
References: <2137@otc.otca.oz>
Organization: HP Andover Division (Massachusetts)
Lines: 19

>In article <5972@mint17.UUCP> wilner@motcid.UUCP (Corey S. Wilner) writes:
>>From what I understand, using the 60Hz line as a reference for timing is not
>>a good practice if you want any accuracy.  I have heard that cycles can be
>>longer or shorter than 1/60th of a second and some cycles can be lost completely.
>
>Power frequency varies a bit in the short term to suit the power companies'
>convenience, but over the long term it is *extremely* accurate, referenced
>to atomic clocks and very carefully kept spot-on.  They even crank in the
>leap seconds.

Eh??  Why do leap seconds matter when all you are controlling is the
(integral) number of cycles in a single second?  Or do you mean that
they actually slow things down a bit so that people with clocks
running off the power line don't have to insert the leap second by
other means?

Bill Ossmann
HP Imaging Systems
ossmann@hp-and.an.hp.com