Newsgroups: sci.electronics
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: Sidereal Time Clock
Message-ID: <1991Jan4.161950.3317@zoo.toronto.edu>
Organization: U of Toronto Zoology
References: <5711.277c4a63@nuhub.acs.northeastern.edu> <5972@mint17.UUCP>
Date: Fri, 4 Jan 91 16:19:50 GMT

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.

(One word of caution, however:  this applies only if your power company is
part of one of the big grids.  Little local outfits with no outside ties
are reportedly a bit sloppy at times.  I'm not sure how many of those are
left, mind you...)
-- 
"The average pointer, statistically,    |Henry Spencer at U of Toronto Zoology
points somewhere in X." -Hugh Redelmeier| henry@zoo.toronto.edu   utzoo!henry