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Re: power-grid physics - clocks



Yes, in a day's time, the 60 Hz is pretty accurate (say 60.000x Hz). But,
if the power company does indeed alter generator speed at the end of the day
to produce the proper number of cycles, the actual accuracy of the 60 Hz may
be considerably less than 5 sig figs at any given time.

I have heard this story about power companies adjusting generator speed to
produce the proper number of cycles per day from several different sources.
Is it true???

Oren Quist
South Dakota State

-----Original Message-----
From: Edmiston, Mike [mailto:edmiston@BLUFFTON.EDU]
Sent: Thursday, August 21, 2003 11:18 AM
To: PHYS-L@lists.nau.edu
Subject: Re: power-grid physics - clocks

One satisfying way to explain this to students is to talk about the
typical consumer synchronous clock. An electric clock using 60 Hz po=
wer
as its time base is pretty accurate. There are 86400 seconds in a da=
y.
In order for a clock to run within one second per day the daily
frequency accuracy must be within one part per 86400 or roughly 0.001=
%
or roughly 60.00x Hz and approaching 60.000x Hz. I believe this is t=
he
correct ballpark. Our synchronous clock in the science building lobb=
y,
as periodically checked against NIST, is generally better than one
second per day barring blackouts and other power glitches.

Michael D. Edmiston, Ph.D.
Professor of Chemistry and Physics
Bluffton College
Bluffton, OH 45817
(419)-358-3270
edmiston@bluffton.edu


Tom Bross wrote...

What could I tell students are the number of significant figures in t=
he
frequency of the AC available in the lab outlets? Is is 60 Hz, 60.0 =
Hz,
60.00 Hz, etc.? At least what would be a reasonable estimate?