Magnus Danielson wrote:

I keep hearing, on this group, that the powerline is no longer sync'd to utc, and evidence for
that fact being a lack of motorized wall clocks.  Well, clocks that sync to the powerline are in
universal abundance in the US.  Virtually every clock on kitchen appliances is sync'd this way.
The clocks on VCR's may be reset from time to time by a tv station, but the timing signal is
still the powerline.  Basically, any appliance, or device that plugs into the powerline is likely to
use the powerline for its timing function.

-chuck

basis, so it may be

utc, and evidence for

to the powerline are in

appliances is sync'd this way.

the timing signal is

the powerline is likely to

Correct, my measurements clearly show that
mains power is steered to UTC. See:
http://www.leapsecond.com/pages/mains/

If there's anyone from the power industry on the
list I'd be interested to hear first-person technical
details of how phase is synchronized, both short-
and long-term.

But I'm not sure I agree with your claim about
kitchen appliances. It seems to me almost every
kitchen, electronic, wall-clock, and entertainment
appliance being sold these days uses quartz-based
clocks, regardless if they are mains, wall-wart, or
battery powered. I'm not sure how to confirm the
accuracy of this hunch, though.

I suspect there are several factors in the trend
away from mains-clocks to quartz-clocks:

1. Digital or analog quartz movements are dirt
   cheap (so it's a cost saving measure).

2. If the product is intended for sale in Japan
   (where both 50 Hz and 60 Hz mains co-exist).

3. If the product is intended for sale world-wide
   (there is a healthy mix of 50 vs. 60 Hz and 120
   vs. 240 V across the planet).

4. The explosion in the use of switching power
   supplies in home electronics (which are immune
   to local voltage / frequency conventions).

5. The explosion in the use of microprocessor
   based control of appliances (where the CPU(s)
   are driven by an n MHz XO and date/time/display
   functions are managed in firmware).

/tvb

Tom Van Baak wrote:

I am just relating my experience with having mucked about
in the insides of these appliances.  Some are quartz,
but those are generally the sort that have an alarm clock
feature (coffee makers)  Any that blink up at 12:00, or,
lose time while the power is off are most certainly AC
derived.

My most recent exposure to an appliance clock is in a
high end electric "double oven" made by DCS.  It uses
a powerline derived clock on its controller board.  The DCS
uses the same controller board as do the GE, Dacor, Kenmore,
and numerous other ovens.  The ovens are of current manufacture.

You can be almost 100% certain that all domestic ovens
will use line derived clocks.  It would take one heck of a
crystal to remain accurate when exposed to the temperature
variations that exist around such a device's controller board.

-Chuck

Let's see, your graph shows for that small time interval that the frequency
is within 0.05% of being correct.  If it continued at that rate of error,
it would result in an error of about 42 seconds in 24 hours.    Sounds pretty
bad, until you factor in a few other variables.  One, the accuracy of the spectrum
analyzer you used to measure the plot, and the other is the fact that the powerline's
variation is cyclical by design.  Your spectrum analyzer appears to be soundcard
based.  The absolute accuracy of such a system is not so good Soundcards don't
even trim their crystals for frequency.  I would venture that the typical accuracy of
a sound card's clock is certainly no better that +/-0.01%.  If you plot the
powerline frequency over  a longer period, I believe you will find that it keeps coming
back to reality.  The usual pattern for summer time is to lose time during the day, and
to gain it back during the night.  Winter is usually the opposite.

In a synchronization problem such as the one the OP was trying to solve, you would
use the best characteristics of a xtal oscillator, and the power line in arriving
at your solution.  Since the powerline is cyclical in its error, and the crystal is usually
a very slow long term drift you should base your correction on perhaps weeks of
observation of the powerline signal.

-Chuck Harris

Alberto di Bene wrote:

From: "Tom Van Baak" tvb@leapsecond.com
Subject: Re: [time-nuts] Low cost synchronization, kitchen appliances
Date: Sun, 21 Aug 2005 07:03:56 -0700
Message-ID: 000401c5a659$2caf18e0$7a18f204@computer

I think you are makeing the wrong conclusion, just because some powergrids is
steered to match UTC does not mean that all powergrids is steered to match UTC.
Similar is the discussion relating to cellular phones, just because some have
it others may not have it.

I know who to talk to, at least for a deep understanding of the US power-grid.
I had him explain how the power-grid shutdown in east US could possibly occur,
very enlightening I might add. Frequency correction methods where explained in
the theory part of the explanation. The short story is that frequency
regulation is performed by balacing energy production and energy consumption in
the powergrid as a total. Overproduction results in higher frequency, under-
production results in lower frequency. Over and under production is produced
and shared among the producers in order to maintain overall frequency.
This comes at a price (coordination) and the larger powergrid the less eager
to coordinate one might be. I'll see if I can't dig up his post. However, that
would only give some theory and some detail relating to the US situation, but
people live elsewhere and situation is thus different (besides different
frequency and voltage).

Simple. Use a frequency synthesizer, poweramp and a variable transformer in
backwards and then adjust frequency and see if the the clock speed changes
accordingly. I think for most things, a 32 kHz oscillator is being used, since
it can be used for simple processors too.

Markets are global now. Also, there is some odd frequency (such as 24 Hz) grids
still in operation in the US if I recall things correctly.

I agree with all these points. There are really few things that effectively
depends on it, so these days control of the frequency is not as important as
it used to be back in the old days when the industries punch-out and wall
clocks all had their frequency from the mains.

With that background, releasing the "tight" control becomes less of a problem
than it used to be, for good and bad.

I think I recall Poul-Henning mentioned that Nord Pool removed their frequency
control some time back. Maybe I should measure the frequency locally. I can
make some investigation of the local situation.

Cheers,
Magnus

Chuck Harris wrote:

Hmmm, the sound card used is the M-Audio Delta 44, a professional sound
card, used also by musicians and composers for studio works. I don't
know the accuracy of its time base, but certainly it is quite good.

Of course. I have added another plot to that page, taken half an hour
later, and things now look better. And I have beside my bed an alarm
clock driven by the 50 Hz of the mains (I know this for sure, it was
written on the instructions), and I have to reset it very, very seldom.
The seconds are not displayed, just the minutes, and I reset it when the
error is greater than 1 minute, compared to my DCF-77 clock.
So the short term accuracy of the mains seems to be quite bad, but by
averaging on a long period things get definitely better...

73  Alberto  I2PHD

Alberto di Bene wrote:

No doubt, but even the best most gifted world class musician with
perfect pitch cannot resolve pitch to  better than 1 cent.  More usual
is around 4 cents.

Now to screw up a little math and figure out what that means:

A cent is 1/100th of the spacing between two semitones, and because
there are 12 semitones in an octave, there are 1200 cents in an octave.
The cent is, as such, logrithmic in nature.  The ratio of any two frequencies,
given in cents is:

n = 1200 log2(a/b)

If our sound card is accurate to 0.01%, the ratio of a/b would be:
1.0001  so,

n = 1200 log2(1.0001) = 1200 log2(10) log10(1.0001) = 0.03 cents!

0.03 cents is merely 33 times more precise than the very best of the
best can hear!  So, I think I would be safe in concluding that your sound
card may be super duper as a music processing device, and still be pretty
awful as a test instrument.

-Chuck

In message 430879AD.6060508@erols.com, Chuck Harris writes:

For the NordPool area (Norway, Sweden, Denmark, Finland) nobody tried to keep
the average at 50Hz.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

From: "Poul-Henning Kamp" phk@phk.freebsd.dk
Subject: Re: [time-nuts] Low cost synchronization
Date: Sun, 21 Aug 2005 19:21:28 +0200
Message-ID: 58496.1124644888@phk.freebsd.dk

Which is what I recalled that you where saying. This is again my point, that
just because it is in one place, that is not universally true for all places.
The reasoning why people don't care as much should be fairly evident from the
discussion so far.

Also, how do you encode a leapsecond over 50 Hz, 60 Hz or whatever and has it
been done?

Poul-Henning and I both live in the NordPool controlled powergrid.

BTW, measuring the 53rd overtone frequency may not give a clear picture of the
frequency deviations at the base frequency. Overtone spectras experience quite
a different phase shift from the way it is produced by a number of devices
which vector-add to become the seen frequency and phase. Turn on or off a
strong producer of that frequency may shift that phase quite a bit while the
fundamental is barly shifted.

Cheers,
Magnus