Low cost synchronization
John Ackermann N8UR wrote:
One thing I want to explore is how difficult it would be to provide an
external clock for the Delta 44. Higher-end boards in the M-Audio
series have a "wordclock" input, and I suspect that the Delta 44 PC
board may be hackable to enable that.
If you succeed in that, please report your results here (or, if deemed
of no general interest, send me a private message). I could then derive
the clock for the Delta 44 from my Z3801A. thanks.
73 Alberto I2PHD
Poul-Henning Kamp wrote:
In message 4308F567.3020205@erols.com, Chuck Harris writes:
However, I have never, ever heard of anyone that could prove to
do better than 1 cent. Do you have any reference to your claim? Perfect
pitch has always been something that has fascinated me, if only because
of the total unlikeliness of the whole thing.
I met a violinist some years back who suffered from a 440Hz tinitus on his
left ear. When he tuned his fiddle after that, it was 440.0Hz measured
with a frequency counter.
Did you make this measurement, or were you just told of it? What was the
repeatablity?
1 cent sharp at 440Hz is approximately 440.25Hz
1 cent flat at 440Hz is approximately 439.75Hz
(1 cent at any freq = 1: 2**(1/1200) = 1.0005777895)
The pitch one gets out of an open A string on a fiddle varies more than 1 cent depending
on how you support the neck of the instrument, how hard you bow the string,
where you bow the string, and what day of the week it is...
Even playing very softly, my violin is drastically louder than my tinitus.
-Chuck
Here's the story on frequency regulation of power lines:
You can control a few synchronized generators to an external
time standard. You will not be able to get phase control
unless the electric loads are steady. Think of the load
variations as you would temperature variations, except the
load can pull the generator out of phase with the external
frequency. And you can't insulate a generator from its load.
Power companies bill on time-integrated power - watt-hour
meters in the US. Watt-hour meters are still mostly driven
by electric clocks, in a way. The frequency does matter.
Power networks, large or small, cannot be automatically
controlled for frequency - especially not by independent
controllers in each powerhouse. Instead, the network is phase
controlled by the use of synchronous generators. Any single
generator will exchange energy with the network to hold
itself in phase with the network.
If the loads on the network do not match the steam power from
the power plants, then the whole network will rise or fall in
frequency until it reaches a balance of power. This is why
under-frequency relays are used to disconnect plants and loads
from the network in order to save part of the network.
The balance of power is so important that network dispatch
centers monitor generated and consumed power, doing what they
can to maintain balance. They usually lose frequency during the
day when loads are large. As the loads fall off during the
night, excess generated power is used to raise the frequency.
The frequency changes do not exceed 0.1% in large networks.
The basis for controlling the frequency is a cycle-counting
clock that is compared to a time standard. The goal is to have
the clocks match once every 24 hours. This assures fair allocation
of the cost of power - it isn't something that the dispatchers
just do for fun on the night shift.
Based on this:
-
It is unlikely that any power network just lets itself go,
with no standard time/frequency to hold. The under-frequency
relays would make that hazardous. -
Point measurements of line frequency are pointless. The
cycle count must be integrated over 24 hours. I don't know
what time the dispatchers aim for to match clocks. Back in the
fifties I was taught that the time of minimum activity is 4:30
AM, according to an Air Force study of the best time to bomb.
Traffic counters confirm this number. -
Leap seconds are easily integrated into the cycle count
during the following 24 hours.
Regards,
Bill Hawkins
In message 43090342.8000301@erols.com, Chuck Harris writes:
I met a violinist some years back who suffered from a 440Hz tinitus on his
left ear. When he tuned his fiddle after that, it was 440.0Hz measured
with a frequency counter.
Did you make this measurement, or were you just told of it? What was the
repeatablity?
I did.
The pitch one gets out of an open A string on a fiddle varies more than 1 cent depending
on how you support the neck of the instrument, how hard you bow the string,
where you bow the string, and what day of the week it is...
We measured the tone he produced and asked him to make it as steady as possible.
--
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.
In message 001301c5a6a2$74803840$0500a8c0@darius.domain.actdsltmp, "Bill Hawkins" writes
:
Power companies bill on time-integrated power - watt-hour
meters in the US. Watt-hour meters are still mostly driven
by electric clocks, in a way. The frequency does matter.
Uhm, sorry, that is just plain wrong. The Ferrantis (sp?) power
meter which is the most widely used meter in the world is not
frequency sensitive within a band of +/- 10% or more.
- It is unlikely that any power network just lets itself go,
with no standard time/frequency to hold. The under-frequency
relays would make that hazardous.
Does not follow.
--
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.
Poul-Henning Kamp wrote:
In message 001301c5a6a2$74803840$0500a8c0@darius.domain.actdsltmp, "Bill Hawkins" writes
:
Power companies bill on time-integrated power - watt-hour
meters in the US. Watt-hour meters are still mostly driven
by electric clocks, in a way. The frequency does matter.
Uhm, sorry, that is just plain wrong. The Ferrantis (sp?) power
meter which is the most widely used meter in the world is not
frequency sensitive within a band of +/- 10% or more.
I have never seen a power meter made by Ferranti in the US. Landis-gyr,
definitely, but not Ferranti. To quote Landis-gyr's website:
" Landis+Gyr Inc. is the world's leading supplier of electricity revenue meters.
Our products include solid-state and electromechanical residential meters,
a full line of solid-state commercial and industrial meters, high-end precision
meters and extensive automated meter reading (AMR) solutions. "
You cannot make a credible claim of "the most widely used meter in the world"
without including the US. We certainly have as many power meters
as all of Europe.
Here most of our meters are of the induction type, which work on the principles of a
split-phase induction motor. They are very easy to recognize by their
horizontal 4 inch corrugated aluminum disk that rotates (hopefully) slowly.
With the induction type power meter, power line frequency is very
important in determining the "hours" part of kilowatt-hours.
A 10% variation in line frequency would cause a 10% variation in power
consumption registered. Induction type power meters will remain accurate
with a 10% variation in power line voltage, however.
Someday, our utilities will convert all of our meters to solidstate units which might
not be so frequency sensitive, but that will be a few hundred billion dollars from now.
-Chuck Harris
Poul-Henning Kamp wrote:
In message 43090342.8000301@erols.com, Chuck Harris writes:
I met a violinist some years back who suffered from a 440Hz tinitus on his
left ear. When he tuned his fiddle after that, it was 440.0Hz measured
with a frequency counter.
Did you make this measurement, or were you just told of it? What was the
repeatablity?
I did.
Good, then you should remember some important details:
Could he see the counter, or was the test done blind?
What variety of counter (cycle counting, or reciprocal) ?
What was the pitch variance from 440.0Hz?
How did you deal with all of the sympathetic resonances
that naturally occur within a violin?
-Chuck
In message 4309DA8E.9040801@erols.com, Chuck Harris writes:
Uhm, sorry, that is just plain wrong. The Ferrantis (sp?) power
meter which is the most widely used meter in the world is not
frequency sensitive within a band of +/- 10% or more.
I have never seen a power meter made by Ferranti in the US. Landis-gyr,
definitely, but not Ferranti. To quote Landis-gyr's website:
Sorry, not "Ferranti", but "Ferraris" and not "made by", but "principle".
You can read about it here:
http://content.honeywell.com/sensing/prodinfo/solidstate/application/006464_1.pdf
Here most of our meters are of the induction type, which work on the principles of a
split-phase induction motor. They are very easy to recognize by their
horizontal 4 inch corrugated aluminum disk that rotates (hopefully) slowly.
That is exactly the kind I'm talking about, only they're not exactly split-phase
because the offset fields are current vs voltage.
Their frequency sensitivity is very low compared to other error
factors. Most of the installed meters are class 2 (ie: up to 2%
wrong) or worse and frequency is seldom allowed to fluctuate +/- 1%
in any civilized grid.
--
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.
Chuck Harris wrote:
A 10% variation in line frequency would cause a 10% variation in power
consumption registered. Induction type power meters will remain accurate
with a 10% variation in power line voltage, however.
Someday, our utilities will convert all of our meters to solidstate
units which might
not be so frequency sensitive, but that will be a few hundred billion
dollars from now.
In Italy, almost all of the meters have been replaced by solid state
units, which are read remotely through signalling on the power lines. I
feared that would have meant an increase in radio noise (I am a
radioamateur), but so far I haven't noticed any. This system has the
advantage that now the electrical company can apply different rates
between day and night, without needing that the meter itself is able to
keep the count of the time. At the start of each period a remote command
changes the rate.
73 Alberto I2PHD
In message 4309DDC2.3020806@erols.com, Chuck Harris writes:
Poul-Henning Kamp wrote:
In message 43090342.8000301@erols.com, Chuck Harris writes:
I met a violinist some years back who suffered from a 440Hz tinitus on his
left ear. When he tuned his fiddle after that, it was 440.0Hz measured
with a frequency counter.
Did you make this measurement, or were you just told of it? What was the
repeatablity?
I did.
Good, then you should remember some important details:
Could he see the counter, or was the test done blind?
I'm not that daft buddy! :-)
Yes, we didn't mess around, and yes, he could do it.
We measured with 500msec period counting.
--
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.