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- -----Original Message----- From: time-nuts-request <[email protected]> To: time-nuts <[email protected]> Sent: Sun, Nov 17, 2013 9:53 am Subject: time-nuts Digest, Vol 112, Issue 50 Send time-nuts mailing list submissions to [email protected] To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to [email protected] You can reach the person managing the list at [email protected] When replying, please edit your Subject line so it is more specific than "Re: Contents of time-nuts digest..." Today's Topics: 1. Re: Mains frequency (Bill Dailey) 2. Re: Mains frequency (Tom Van Baak) ([email protected]) 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 <[email protected]> To: Discussion of precise time and frequency measurement <[email protected]> Subject: Re: [time-nuts] Mains frequency Message-ID: <[email protected]> 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 <[email protected]> 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 > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ------------------------------ Message: 2 Date: Sat, 16 Nov 2013 23:21:07 -0500 (EST) From: [email protected] To: [email protected] Subject: Re: [time-nuts] Mains frequency (Tom Van Baak) Message-ID: <[email protected]> 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" <[email protected]> To: "'Discussion of precise time and frequency measurement'" <[email protected]> Subject: Re: [time-nuts] Loran Message-ID: <00d901cee398$33201dc0$99605940$@[email protected]> Content-Type: text/plain; charset="US-ASCII" Still on at 1300z Sunday Bill Riches Cape May -----Original Message----- From: [email protected] [mailto:[email protected]] 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 <[email protected]>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 [email protected] +1.916.877.5067 _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ------------------------------ Message: 4 Date: Sun, 17 Nov 2013 09:57:52 -0500 From: "jmfranke" <[email protected]> To: "Discussion of precise time and frequency measurement" <[email protected]> Subject: [time-nuts] national nc2001 atomic clock on eBay Message-ID: <DEB385E9D32D4DA9AE79B017CD5FDEFC@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" <[email protected]> To: "Discussion of precise time and frequency measurement" <[email protected]> Subject: Re: [time-nuts] national nc2001 atomic clock on eBay Message-ID: <36CB89FB711D43BFA1EB833F4F4BB2CF@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 <[email protected]> To: Discussion of precise time and frequency measurement <[email protected]> Subject: Re: [time-nuts] Loran Message-ID: <cae3hgtcoctfcrkdddknxpfkwzqvgvnq9wg-eez5e9etftr1...@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1 On Sun, Nov 17, 2013 at 7:23 AM, bill.riches <[email protected]>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 [email protected] +1.916.877.5067 ------------------------------ Message: 7 Date: Sun, 17 Nov 2013 07:52:37 -0800 From: "Tom Van Baak" <[email protected]> To: "Discussion of precise time and frequency measurement" <[email protected]> Subject: Re: [time-nuts] Mains frequency (Tom Van Baak) Message-ID: <69D79F41AD2C45059E64A3A3B8EA4DC7@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 -------------- next part -------------- A non-text attachment was scrubbed... Name: mains-dailey-3.gif Type: image/gif Size: 36873 bytes Desc: not available URL: <http://www.febo.com/pipermail/time-nuts/attachments/20131117/f72112b9/attachment.gif> -------------- next part -------------- A non-text attachment was scrubbed... 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