[time-nuts] Re: UTC
cfmd at bredband.net
Sun Jul 31 11:49:49 EDT 2005
From: Warner Losh <imp at bsdimp.com>
Subject: Re: [time-nuts] Re: UTC
Date: Wed, 27 Jul 2005 17:19:34 -0600 (MDT)
Message-ID: <20050727.171934.28808808.imp at bsdimp.com>
> > Certainly. But what's your point? I don't see these utilities failing
> > if a second slips here or there. The one case where time is critical
> > is the power grid, and they keep their own time (Which, IIRC
> > approximates UTC).
> The long term average of the power grid in the US is 60.000 Hz. Short
> term variations from that can and do happen.
Actually, assume that the short-time frequency is most probably anything but
60 Hz (or 50 Hz, depending on where you are). The over and under-production of
electricity is the frequency control-means.
> It is to make sure that the clocks run on time, on the average. It might be
> better to say that the power grid approximates the SI second, since it has no
> notion of which second it is (although the control infrastructure for the
> grid most likely does).
Rather, you have on long term average a frequency control, but no phase
My oldest counter had in standard edition the 50 Hz or 60 Hz power grid
frequency as reference frequency (using a phantastron frequency divider
circuit using a pentode and a triode) where as mine has the 100 kHz crystal
oscillator reference, when that was a luxuary. ;O)
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