Re: [time-nuts] Recording mains frequency/phase [WAS: No GPSsatellites]
Dave, That's cool. I am the dot just above the US / Canada border and just below the Ontario/Quebec border in Eastern Ontario. There are many (many) documents that can found using Google on the subject of power grids and frequency and monitoring. I have only been able to read through only a small handful. An interesting application of time and frequency measurement. cheers, Graham ve3gtc On 2015-02-28 19:50, DaveH wrote: Like this? http://fnetpublic.utk.edu/gradientmap.html I am the dot just below the Canadian border in WA State. Dave -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Philip Gladstone Sent: Friday, February 27, 2015 07:47 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Recording mains frequency/phase [WAS: No GPSsatellites] On 2/26/15 20:39, Charles Steinmetz wrote: ben wrote: I'm going to have to build one of these. Assume you have some sort of circuit that converts low-voltage AC from a transformer secondary to a pulse train, start a timer, and count x amount of pulses? Here is a zero-cross detector designed for this purpose: http://www.ko4bb.com/manuals/download.php?file=02_GPS_Timing/ Simple_AC_Mains_Zero_Crossing_Detector.pdf Most mains-nuts feed the ZCD pulse to the DCD line of a PC's RS232 port and use the computer to time-stamp the crossings and append them to a file of such time stamps. If we all did this, then I realize that we could identify the different power grids. However, I wonder if there is any interesting variation *within* a grid. As the electricity flows vary throughout the day, it seems possible that the phase difference between two people on the same grid would actually change (a bit). Has anybody done this experiment? Philip ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] homebrew counter new board test result
Tom, On 02/28/2015 06:10 PM, Tom Van Baak wrote: A good paper to read about the trouble when DUT is close (or equal to REF) is: http://literature.cdn.keysight.com/litweb/pdf/5990-9189EN.pdf Isolating Frequency Measurement Error and Sourcing Frequency Error near the Reference Frequency Harmonics Nice reading and illustration of the problem. It does not go into explain where these errors come from. I especially like that he worked on an offset frequency to handle source issues and that he elaborates with both time-base time and frequency offset, as well as average and peak-to-peak values. Have you seen any papers going into depth about that? The Robert Leiby (5990-9189EN) paper was a real find. Agilent sent it to me after I ran tests of their new 53230A counter. I had two of them on loan (TCXO and OCXO) and the closer I looked the less I was impressed. The one feature that was a show-stopper for me was that the TCXO version would not outperform the OCXO version even if you gave it a BVA or maser as external reference to the counter. That means in order to get decent performance out of the 53230A you must buy the overpriced OCXO version of the counter. I wonder if anyone else has run into this? Maybe my eval units were out of spec. Or, I wonder if anyone has opened their 53230A and hacked the timebase PLL to overcome this problem? Anyway, that led to me checking out a pile of 53132A counters to see how well they performed. Yes, it makes good sense to follow up with those. The paper is indeed a good find. In these tests I like to use slightly drifting, ultrastable, independent inputs instead of the old BNC tee trick where CH1=CH2 or CH1=CH2=REF. What you want is to see is not only the RMS noise in a measurement, but also how consistent the TI measurements are across the entire fundamental period of the inputs or timebase. Indeed. The time error over the time-base period is relevant to measure, but also you have cross-talk from time-base into channels as well as cross-talk between channels. For the frequency case, you might not expect there to be cross-talk, but there will be if the frequency measure uses the start and stop channels. For my test I used two ultrastable sources with 1e-12 or 1e-11 frequency offset. At 1e-11 you can scan an entire 100 ns period in 10,000 seconds (under 3 hours). I'd have to look at my notes to see what I did with the REF input. I think I tried REF=CH1 and REF=CH2 and REF=3rd independent source. But the main goal was to see the interaction between CH1 and CH2 because that's the mode used by any TI measurement. Indeed. It can be hard to separate the non-linearity of a channel (over the time-base period) from the cross-talk from reference to channel. The non-linearity usually has a periodicity over the time-base reference due to the use of a coarse counter frequency (such as 90, 100, 200 and 500 MHz) where as some (HP5335A, HP5334A/B) uses the time-base directly as coarse counters. Enrico have been looking at post-processing filtering, and it's effects. I just haven't seen any paper giving much about how cross-talk and such affects non-linearity and post-processing such as frequency reading and ADEV. I have my own model from experience and various sources, but not seen anything comprehensive. Cheers, Magnus Right, there's no paper that I could find yet. Instead I was planning on taking several models of popular high-end TI counters (SR620, HP5370, CNT-91, 53132A, 53230A) and run them all through the same offset/linearity test to investigate the fine structure of their measurement errors, as was done in the Leiby paper. If you have some measurement setup suggestions beyond what I already did with the 53132 counters, let me know. Leiby's paper is focused on the frequency measurement and in particular the non-linearities of the hardware in relation to frequency measurements. The underlying model is time errors and considering that the frequency estimate f = events/(t_stop - t_start) the non-linearities in the time estimations t_stop and t_start will be subtracted from each other. As the number of complete cycles of error increases with tau, the remaining time error within such a period will be divided by a tau. Consider the period formula t_period = (t_stop - t_start)/events Consider that events = tau*f_1, t_start = 0 + te_start, t_stop = tau + te_stop (approximation for understanding) we get t_period = 1/f_1 + (te_stop - te_start)/(tau*f_1) No wonder that the period (and thus frequency) measure errors varies with tau and measured frequency. Rather than measuring with free-floating oscillators, I have been considering using frequency syntesizers as in Leiby's article and programmable delays. That way I can stay at a particular delay and bang the same point and get statistics. The histogram will give me information about the offset and coupling properties. I think this could be an interesting paper maybe.
Re: [time-nuts] Recording mains frequency
Just a thought about interpreting data: The mains frequency changes as the loads on the system change. Dispatchers bring more generators on line or drop them. Some of this is predictable, depending on business hours, weekends, holidays and the seasons. Just as one can take the crystal aging out of the frequency vs. time display, it should be possible to subtract an average of the variations caused by predictable load changes. This leaves a display that makes unusual deviations much more visible. The line frequency is not like a disciplined crystal oscillator. There is no phase locked loop adjusting the line frequency, just dispatchers trying to produce the same number of cycles per day. The length of a day is precisely known from national time standards. Short term plots (e.g. daily and weekly) of line frequency should be referenced to time of day, not elapsed time. It would be interesting to see how the daily load averages vary from region to region. Bill Hawkins ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Recording mains frequency/phase [WAS: No GPSsatellites]
On 2/27/2015 1:27 PM, Tom Van Baak wrote: There are many wonderful web sites that deal with power line frequency; some with live plots. Just google for words like: mains frequency detect accuracy stability measurement Been doing just that - fascinating! I'm getting closer to doing some frequency / phase monitoring here. From: http://leapsecond.com/pages/mains-cv/ A convenient way to monitor power line phase or frequency is to timestamp every cycle. This generates a lot of data...so for most purposes we keep just one timestamp per second. This gives about 86400 samples per day. Using a zero-crossing detector with the picPET and logging the timing of each zero-crossing, how do you toss out the other 59 samples each second? Doing this after-the-fact seems do-able with some software. I seem to recall doing something like this with FORTRAN or BASIC. (open log file, open output file, read log file line by line, tossing out 59 samples and writing the 60th to the output file, reach EOF, close both log and output file) But...is there a clever way to do it up front? Time to do more reading. I've seen some folks doing frequency / phase monitoring using an Arduino, but nothing (yet) that uses a high-precision reference such as 10 MHz from a GPSDO. On a side note...the Z3801 got a new outdoor GPS antenna yesterday. Very happy with how well it is working: http://www.kd5byb.net/kd5bybgpscon/gpsstat.htm thanks much and 73, ben, kd5byb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Measuring frequency rather than tuning crystal
Here is a quote from the TF930/TF960 Service Guide, in the section on calibrating the internal TCXO: Set the Measurement Time to 1s and repeat the process. The adjustment per step is now a decade smaller and multiple presses may be needed. The measurement restarts after each set of key presses. It will take a few seconds for the reading to stabilise because of the settling time of a filter on the control voltage. Aim to be within about 0.5Hz and then move to the next step. The reference to the control voltage strongly suggests that it is actually adjusting the timebase frequency via the frequency control input, not adjusting a numerical constant. We know that the TCXO is actually a VCTCXO, because it can be phase locked to an external reference. And we know it's actually phase locking the internal reference when an ext. ref. is supplied, not merely substituting the external reference in place of the internal one, because the manual says that the external reference must be a high-accuracy 10 MHz signal - it is not possible to use a different reference frequency. (There is more detail - see the External Reference section of the 930 or 960 manual). - Dave On Fri, Feb 27, 2015 at 4:23 PM, Dave Martindale dave.martind...@gmail.com wrote: The TF930/960 does have a calibration procedure that is performed from the front panel. Basically, you feed it a stable input from any known source (so both 1 Hz and 10 MHz from a GPSDO should work) and then adjust until the displayed frequency agrees with the known input frequency. The resolution of this setting is quite a bit better than the stability of the TCXO in the box. Now, this process could occur either by actually adjusting the frequency of a VCTCXO in the box using a DAC, or by changing a calibration constant stored in the memory of the device. I suspect it's actually the former, because the instructions say that the adjustment path has a low-pass filter that you need to allow to settle. This wouldn't be necessary if the calibration simply changed a stored number. Dave On 27/02/2015 15:08, Paul Alfille wrote: I don't think your TTi TF930 has a GPS input to calibrate against, based on a quick perusal of the data sheet. I would guess that the calibration constants are thus fixed from the factory (including temperature coefficients). On Thu, Feb 26, 2015 at 3:36 PM, James via time-nuts time-nuts@febo.com wrote: I presume that this is what my TTi TF930 does. Calibration is closed box so I guess the TCXO is free running and the micro inside just uses calibration constants. James -Original Message- From: Paul Alfille paul.alfi...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thu, 26 Feb 2015 19:02 Subject: [time-nuts] Measuring frequency rather than tuning crystal I have a couple of HP 5370s with the beaglebone brain transplant. They come with a nice 10811 that has a little adjustment screw. Testing against a Thunderbolt or KS-24361 the 5370 is off by less than 1Hz. I know the traditional method would be to adjust the crystal slowly and make careful measurements, but since I have a fancy computer in there, I wonder if I could just adjust the frequency in software. 64-bit floating point numbers should have sufficient accuracy. All reported measurments would be corrected for the actual reference frequency. Basically, I'd have a 1000.226 Hz internal reference. In fact, could I connect the beaglebone to a a GPS 1 pps source and make this a GPS-disciplined-software-corrected oscillator. So my question is is this a known technique? The discipline feedback circuit seems a little different, I'd adjusting for drift and offset, but not the gain of control-oscillator linkage. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Monsanto IC
Looks like a rebadged Schlumberger Unit to me. (Case style wise) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] simple explanation of noise spectra with mixing
time-nuts Digest, Vol 128, Issue 1, Message: 8 Date: Sat, 28 Feb 2015 17:46:18 -0800 From: Jim Lux jim...@earthlink.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] simple explanation of noise spectra with mixing, etc. Message-ID: 54f26f6a.6030...@earthlink.net Content-Type: text/plain; charset=utf-8; format=flowed Is there a handy one pager kind of explanation of noise spectra after some forms of signal processing.. The best source for the math is probably Fred Walls: F. L. Walls, “Correlation between upper and lower sidebands” IEEE Trans. UFFC, Vol. 47, pp 407-410, 2000. PM and AM Noise of Combined Signal Sources, Fred L. Walls, Total Frequency, fredlwa...@cs.com, Proceedings of the 2003 IEEE International Frequency Control Symposium and PDA Exhibition Jointly with the 17th European Frequency and Time Forum, 0-7803-7688-9/03/$17.00 © 2003 IEEE, pages 532-540. For instance, if you have a oscillator which has a 1/f characteristic, and you mix it with itself, what is the spectra of the output of the mixer. Mixing is a multiplicative process, so this is equivalent to squatting the signal, which doubles its frequency, so the effect will be 20 Log10(2)= 6 db increase of phase noise on the double-frequency terms. Your bottom-line question will be if there is any cancellation of phase noise; this will involve the time delay for the rata signal to get to the target and return. My guess is that there will be no cancellation. Or if you have a 1/f^3 characteristic (e.g. from a crystal oscillator, very close in) or a 1/f^2 (from a VCO). The double rule will apply to each point in the phase noise as if it were alone. Specifically, I've got some folks working with homodyne radars (where you demodulate the received signal with a sample of the transmitted signal, but sometimes with an offset mixed in, etc.) and I'm looking for a quick intro to this kind of thing at a sort of empirical/phenomenological as opposed to analytical.. If you see X on a spectrum analyzer or FFT, it is because of Y... Similarly, they're building PLLs and know about the 20log10(N) thing, but what should the shape of things underneath be. The 20Loh10(N) applies regardless of offset frequency, so the whole phase noise spectrum will move up and down as a unit. Joe Gwinn ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Monsanto IC
Hi, I have friend with a question about an IC badged with Monsanto. I googled a bit and found that there is a big line of older maybe 60's era counter / timers which were made and badged Monsanto. I am asking here if anyone has some of these or have a knowledge of whether they may have custom IC's. It isn't out of the question that this is a custom front end part, or perhaps some part of a timer circuit they may have developed. The ebay link to the part is below, as is a search string for monsanto on Tucker Electronics manual web page. The question if for a friend who has the IC for sale. Any info appreciated. thanks Jim http://www.etestmanuals.com/Search.aspx?Mfg=MON Ebay listing for a monsanto counter / timer VINTAGE-Monsanto-110B-Programmable-Counter-Timer-/ http://www.ebay.com/itm/331268326313 Monsanto IC: Monsanto-SD102-Vintage-Very-Rare-White-Ceramic-Gold-Zebra-Grey-Trace-IC-/ http://www.ebay.com/itm/371270297731 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Recording mains frequency/phase [WAS: No GPSsatellites]
On 28/02/2015 18:09, Tom Van Baak wrote: Hi Daniel, That will be an interesting experiment. I'm happy you are doing it. You may want to run all five boards within the same house first -- to establish your noise floor and to check your post-processing (non-aligned log files, glitches, power fails, oscillator drift, etc.). Surelly... I must first discover how well (or how badly) it works Here's one from a couple years ago, between two cities, and two states. http://leapsecond.com/pages/mains-cv/ Thanks for the link! Daniel /tvb - Original Message - From: Daniel Mendes dmend...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, February 28, 2015 10:34 AM Subject: Re: [time-nuts] Recording mains frequency/phase [WAS: No GPSsatellites] I´m planning an experiment like that... I designed a board with an OCXO, pic microcontroller, power supply, mains interface with optocoupler, and SD card for data collection.. I plan to sincronize a counter running at 10MHz between them and log events at 5 different points in my city. The boards also have a small Li-Ion battery and battery charger for short power outages. Boards are manufatured and the most expensive items have been bought, but not everything yet. Daniel ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Recording mains frequency
On 28/02/2015 16:58, Charles Steinmetz wrote: Daniel wrote: I designed a board with an OCXO, pic microcontroller, power supply, mains interface with optocoupler, and SD card for data collection..* * * The boards also have a small Li-Ion battery and battery charger for short power outages. Boards are manufatured and the most expensive items have been bought, but not everything yet. I'm not a grid-nut myself, but your project sounds very interesting. I designed the simple zero-cross detector because it appeared to me that many potential grid-nuts may be put off by the need to design and construct data collection tools, and I thought that a very simple hardware detector running into an RS232 port might lower this barrier enough to allow more prospective grid-nuts to play. But there is still the matter of receiving, formatting, and storing the raw data, and the need to leave a computer on 24/7. Your hardware solves these issues. Yes... Even at my house it would be cumbersome to let something so big turned on 24/7 (small child, wife). Ask for others to do it just wouldn´t work, so I designed something that fitted into a small box. Can you share the construction details (schematics, firmware, board files)? It´s not assembled yet. Still need to buy about half the components (but the most expensive ones are already in hand). I´m sending the schematics attached (no more... to big for the list... sent directly). When it´s assembled and running i´ll post all the info somewere freelly avaiable (i´m trying to start a blog with all the crazy junk I make...). Do you plan to make boards or kits available? No... but I have spare boards I can send away for free if someone wants them. I just need to discover how to send them from Brazil overseas.. but it can´t be hard. Also, you say you plan to synchronize a counter between them. How do you plan to do that without some sort of common-view timing source at each site (GPS, NTP, etc.), or do you plan to have common-view timing? I plan to sincronize once (when they are powered on and near each other). They will be calibrated as well as I can (I have two 12 digits frequencimeters). After that they can drift away, but I expect that the OCXOs will make that negligible Very interesting project -- congratulations, and please keep us updated. Thanks! Daniel ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] time-nuts Digest, Vol 127, Issue 33
The downconverter was used for long runs of cable typical use case was a high rise with data center in basement As I recall it converted the signal to a high level baseband and amplified that whic was good for a thousand feet or so of cable Content by Scott Typos by Siri On Feb 27, 2015, at 5:14 AM, Al Wolfe alw.k...@gmail.com wrote: I have an XL-DC and it has an internal GPS receiver in it. It supplies and monitors 5 volts to a BNC antenna jack for an external amplified GPS antenna. I don't know what the internal GPS engine is but doubt if it is anything special. The manual describes the down converter system as an option. Al, k9si Boy I ran out to mr google and did a search and now I am wondering if some versions of the xl-dc just used a plain old GPS antenna. It sure looks like that could be the case. The manual does say down converter. Maybe it changed over time. Regards Paul WB8TSL ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
