[time-nuts] Mains frequency (Tom Van Baak)
johncroos at aol.com
johncroos at aol.com
Sun Nov 17 16:37:10 UTC 2013
Tom -
Attached is an example from mains data that Bill just collected with picPET and
that TimeLab plotted.
I really got to get one of these one day. Thanks for the lead.
-john k6iql-
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Sent: Sun, Nov 17, 2013 9:53 am
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Today's Topics:
1. Re: Mains frequency (Bill Dailey)
2. Re: Mains frequency (Tom Van Baak) (johncroos at aol.com)
3. Re: Loran (bill.riches)
4. national nc2001 atomic clock on eBay (jmfranke)
5. Re: national nc2001 atomic clock on eBay (Tom Van Baak)
6. Re: Loran (Brian Lloyd)
7. Re: Mains frequency (Tom Van Baak) (Tom Van Baak)
----------------------------------------------------------------------
Message: 1
Date: Sat, 16 Nov 2013 21:49:10 -0600
From: Bill Dailey <docdailey at gmail.com>
To: Discussion of precise time and frequency measurement
<time-nuts at febo.com>
Subject: Re: [time-nuts] Mains frequency
Message-ID: <06599006-CE82-476D-B24F-051C9EBFDB23 at gmail.com>
Content-Type: text/plain; charset=us-ascii
This resonates with me somewhat since I used to run nuclear power plants and
operate the actual turbines. It does seem that the time interval measurements
have much more jitter than I would expect. I suspect the thousands of turbines
phase locked may introduce all kinds of very subtle variations. I do know when
you put a submarine turbine on shore power (grid). You no longer have to control
speed... The grid does that for you.
Sent from my iPad
> On Nov 16, 2013, at 9:35 PM, Charles Steinmetz <csteinmetz at yandex.com> wrote:
>
> tvb wrote:
>
>> I think we agree. Just to clarify...
>>
>> I rely on no hardware and no software filters when I use a time-stamping
counter such as a sub-nanosecond Pendulum CNT-9x or sub-microsecond picPET. An
electrical zero-crossing happens when it happens. If you "filter" you're just
trying to change history: spikes are spikes; noise is noise; history is history.
Deal with it. Record it, don't filter it away.
>
> Well, it depends on what one wants to investigate. The "naked" history one
captures with no filtering may not be the cleanest history available of the
phenomenon under investigation. Except in unusual circumstances, mains voltage
is generated by massive rotating machinery -- so anything fast that happens on
your incoming mains voltage is not a reflection of the grid frequency. If what
you want to know is the grid frequency over time (vector sum of the rotational
velocity of the various generators on the grid, as seen from your location), a
filtered and limited signal may (probably will) provide the best assessment.
Note that local zero crossings are only a proxy for grid frequency to begin with
-- and not a very good one, specifically because of the high noise level. Of
course, you can always filter in software if you time-stamp each zero cross in
all its naked glory, but removing the noise prior to time-stamping is often
preferable to digitally processing a noisy capt
ure.
>
> Put another way, the massive rotating machinery that generates the mains
voltage can only change the zero cross of the grid by a tiny amount from one
cycle to the next. If a data capture method shows cycle-to-cycle jitter that is
significantly greater than this amount, the increase cannot be due to the
generators, it can only be due to noise. If one's interest is the grid
frequency, removing this noise prior to time-stamping can only help.
>
> Note that I'm not talking about a filter Q in the millions -- I'd probably be
inclined to use a linear-phase filter with several Hz bandwidth, after a more
rigorous analysis of the application.
>
>> You can either focus on the signal, or the noise. That's two separate plots.
>
> Agreed. If you are investigating incidental noise on the mains rather than
the grid frequency, then the signal you capture needs to be at least as
broadband as the noise in which you are interested.
>
> Since I do not use the actual local mains zero crossings for anything (other
than electronically switching loads on at zero voltage and off at zero current,
where absolute timing is irrelevant), I'm not sure why one might be interested
in characterizing them. OTOH, since I do have equipment that responds to the
grid frequency, I can see practical utility in characterizing that. Hence my
suggestion to filter.
>
> Best regards,
>
> Charles
>
>
>
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------------------------------
Message: 2
Date: Sat, 16 Nov 2013 23:21:07 -0500 (EST)
From: johncroos at aol.com
To: time-nuts at febo.com
Subject: Re: [time-nuts] Mains frequency (Tom Van Baak)
Message-ID: <8D0B16391E9EBFF-1A54-177C5 at webmail-d223.sysops.aol.com>
Content-Type: text/plain; charset="us-ascii"
Tom -
I just had to comment---
Both assume some reasonable limit of mains df/f/dt. You can either
do it with a fancy $100 to $1000 reference signal generator + PLL or FLL + IQ
detector + professional box -- or with a $1 PIC and $0 s/w.
/tvb
You are of course correct. However I would most humbly point out that the cost
of software is not zero if the time-nutter places any value on his or her time.
If you figure your engineering direct labor rate is, for example $ 40 per hour,
and the job takes 15 hours to program - you just blew $ 600 of your life. That
assumes no issues crop up. Now as a private consultant or as a business that
direct labor will be burdened with say about 130% overhead. So we are talking
real money in terms of the value of your time. As a hobbyist you can contribute
the time for free - but do under appreciate its value.
For an olde hardware guy like me (who can sorta program a PIC) a known harware
approach causes me less fear and feeling of dread than the PIC approach. So we
do what we are more comfortable with.
Enjoyable discussion though.
-73 john k6iql
------------------------------
Message: 3
Date: Sun, 17 Nov 2013 08:23:26 -0500
From: "bill.riches" <bill.riches at verizon.net>
To: "'Discussion of precise time and frequency measurement'"
<time-nuts at febo.com>
Subject: Re: [time-nuts] Loran
Message-ID: <00d901cee398$33201dc0$99605940$@riches at verizon.net>
Content-Type: text/plain; charset="US-ASCII"
Still on at 1300z Sunday
Bill Riches
Cape May
-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Brian Lloyd
Sent: Saturday, November 16, 2013 8:23 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Loran
On Sat, Nov 16, 2013 at 7:04 PM, Bill Riches <bill.riches at verizon.net>wrote:
> Wildwood is still up at 0100 z 11/17. Guess they are running all weekend.
>
Looks like it is off the air again.
--
Brian Lloyd, WB6RQN/J79BPL
706 Flightline Drive
Spring Branch, TX 78070
brian at lloyd.com
+1.916.877.5067
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Message: 4
Date: Sun, 17 Nov 2013 09:57:52 -0500
From: "jmfranke" <jmfranke at cox.net>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Subject: [time-nuts] national nc2001 atomic clock on eBay
Message-ID: <DEB385E9D32D4DA9AE79B017CD5FDEFC at Franke>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
http://www.ebay.com/itm/national-nc2001-atomic-clock-/181261183205?pt=LH_DefaultDomain_0&hash=item2a340228e5#ht_41wt_1071
John WA4WDL
------------------------------
Message: 5
Date: Sun, 17 Nov 2013 07:48:52 -0800
From: "Tom Van Baak" <tvb at LeapSecond.com>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Subject: Re: [time-nuts] national nc2001 atomic clock on eBay
Message-ID: <36CB89FB711D43BFA1EB833F4F4BB2CF at pc52>
Content-Type: text/plain; charset="iso-8859-1"
> John WA4WDL
Thanks, John. There are a couple of these still around. I think that particular
specimen was sitting in a remote Minnesota cabin for many years. I have more
photos of it somewhere if anyone is interested. I passed on it due to its weight
and condition.
/tvb
------------------------------
Message: 6
Date: Sun, 17 Nov 2013 08:00:51 -0600
From: Brian Lloyd <brian at lloyd.com>
To: Discussion of precise time and frequency measurement
<time-nuts at febo.com>
Subject: Re: [time-nuts] Loran
Message-ID:
<CAE3hgTcoCtFcRKddDKnXPfKWZqvGVnq9wG-EEz5E9EtFtr1WLw at mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
On Sun, Nov 17, 2013 at 7:23 AM, bill.riches <bill.riches at verizon.net>wrote:
> Still on at 1300z Sunday
>
I am wondering if I am actually seeing the eLORAN station at all. The
frequency of what I am seeing is 100,005.63 Hz. I can't imagine they would
be that far off frequency.
--
Brian Lloyd, WB6RQN/J79BPL
706 Flightline Drive
Spring Branch, TX 78070
brian at lloyd.com
+1.916.877.5067
------------------------------
Message: 7
Date: Sun, 17 Nov 2013 07:52:37 -0800
From: "Tom Van Baak" <tvb at LeapSecond.com>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Subject: Re: [time-nuts] Mains frequency (Tom Van Baak)
Message-ID: <69D79F41AD2C45059E64A3A3B8EA4DC7 at pc52>
Content-Type: text/plain; charset="iso-8859-1"
> You are of course correct. However I would most humbly point out that the cost
> of software is not zero if the time-nutter places any value on his or her
time.
> ...
Hi John,
True. And if you place value on your time then it's best to use existing tools
if possible. The picPET was designed to output plain ascii decimal timestamps so
the data can be processed with a wide variety of existing tools.
For example, John Miles' free TimeLab program will read from a picPET directly.
You can get phase, frequency, and ADEV of the power line -- live on your screen,
with no effort at all.
Attached is an example from mains data that Bill just collected with picPET and
that TimeLab plotted.
/tvb
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