Re: [time-nuts] How did they distribute time in the old days?
I heard of a system used in Melbourne between two major stations using pulses in a pipe of water to sync. I suppose that pulses travel much faster in water being incompressible, so better accuracy! Tom Harris <celephi...@gmail.com> On 20 October 2015 at 07:00, Brian Inglis <brian.ing...@systematicsw.ab.ca> wrote: > On 2015-10-15 08:32, Tom Van Baak wrote: > >> Nick Sayer writes: >> >>> The WU standard time service goes back further than the turn of the 20th >>> century. It started in 1870. >>> >> > Also, for a screen full of irresistible SWCC photos, try this: >> https://www.google.com/search?tbm=isch=self-winding+clock+company >> >> My understanding (perhaps incorrect) was that the sync pulse was once >>> daily and, as you said, >>> would cause the hands to “snap” to 12. The trailing edge of the pulse >>> was synchronized and would >>> release the clock to operate normally. >>> >>> That they had something as accurate and widespread as it was so early is >>> astonishing. >>> >> >> Oh, Padawan, that's just the tip of the iceberg when it comes to the deep >> and fascinating history of precise timekeeping. >> > > Recently restored (after a building fire where some were lost) to working > 19 Art Nouveau master/slave clocks from 1910: > http://www.gsaarchives.net/2013/04/mackintosh-clocks-feature-on-bbc-news/ > more pictures in linked articles from BBC > -- > Take care. Thanks, Brian Inglis > ___ > 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] beaglebones, time, web services
Since you want simple just use a CGI script written in your language of choice. Very easy technology to learn, Python has support libraries out of the box if you want. You have a webpge with carious simple controls on it like buttons etc, you click a special button that posts a request to a URL, the webserver runs a script that generates the response, the webserver serves it out, your browser displays it. Why bother with learning a framework? Messing about with mechanics is far more fun! Tom Harris celephi...@gmail.com On 4 July 2015 at 23:13, Jim Lux jim...@earthlink.net wrote: I've got a project I'm working on to make a sophisticated sundial with moving mirrors. I've got a batch of Arduinos that move the mirrors to the appropriate places, given the current sun angle, etc. I've got a beaglebone that runs some python code to calculate sun angle based on time The beaglebone will have a GPS feeding it to get time. BUT now, I'd like to add a web interface, so that it can be manipulated by a mobile device using a browser. One way I can think of is to run some sort of limited web server. there are a couple that come with the beaglebone, including the python simplehttpserver. But I'm sort of stuck on the interface between the webserver and the other code running. I've done this kind of thing where the one task goes out and updates files in the tree that's being served by the web server, and that works fine for status display kinds of things that don't update very quickly. It's also nicely partitioned. but I want to be able to change the behavior of the system (e.g. by having the server respond to a PUT or something) Is the best scheme to go in and modify the webserver code to look for specific URLs requested, and then fire off some custom code to do what I want? I'm not particularly interested in javascript, and would prefer python. Or are there libraries that make this more cookbook? (the little getting started with beaglebone book talks about flask) There's quite a few websites out there where someone has done some sort of home automation, but they tend to be a bit light on the analysis of pros and cons of implementation architectures: I built X using Y and Z and it sort of works. Actually, along a similar line.. my solar position code isn't very pretty (it's sort of replicating some code I wrote in Basic a long time ago, with some changes from stuff I cribbed from ccmatlab). If someone knows of a python package that just does this, I'd love to hear about it. Either Az El, or X,Y,Z in ECI or ECF would do. ___ 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] Lady Heather leap second display
Sounds like my sort of party. I went to a similar party, the drinks were all served in laboratory glassware and the host did his party trick of drinking liquid nitrogen and rolling it around his mouth so that it did not burn him, and then spitting it out onto the floor where it immediately evaporated. He also dipped people's cigarettes in liquid oxygen, this turns them into miniature firecrackers when lit, all the more fun if they are in someones mouth at the time! The invites had the time/date in Unix seconds since 1970. Tom Harris celephi...@gmail.com On 24 June 2015 at 05:28, Esa Heikkinen tn1...@nic.fi wrote: VK2DAP kirjoitti: I am hosting a small party and don't want to look like a dill more than I already do. Just make sure that UTC time is selected in thunderbolt settings. Check my Lady Heather video from 2012, if there's any help for the settings: https://www.youtube.com/watch?v=DbvMZikqtI4 -- 73s! Esa OH4KJU ___ 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] windows and leap seconds
Hilarious note on the bottom of the document: This is a FAST PUBLISH article created directly from within the Microsoft support organization. The information contained herein is provided as-is in response to emerging issues. As a result of the speed in making it available, the materials may include typographical errors and may be revised at any time without notice. Wasn't the leap second publicised 6 months in advance? Tom Harris celephi...@gmail.com On 25 June 2015 at 02:24, David J Taylor david-tay...@blueyonder.co.uk wrote: From: Jim Lux https://support.microsoft.com/en-us/kb/909614 basically: ignore the leap second, so your computer is fast relative to UTC, and next time you resynchronize time it adjusts Windows, these days, runs NTP http://blogs.msdn.com/b/mthree/archive/2015/01/08/leap-seconds-010815.aspx http://blogs.msdn.com/b/mthree/archive/2015/01/14/leap-seconds-011415.aspx for more info ___ .. although the NTP run by default meets few of the standard NTP functions, as provided by the Meinberg NTP port, which includes smooth leap-second handling. http://www.meinbergglobal.com/english/sw/ntp.htm#ntp_stable http://www.satsignal.eu/ntp/setup.html Cheer, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ 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] magnetic electronic components
The techniques are still alive well in power electronics. Try looking at an introductory textbook on the subject. Engineers with decades of experience in this will design inductors, then trim them by hand to achieve the best results. One old guy would crack toroids in half, and then shim them with multiple cigarette papers to make a gapped core. Tom Harris celephi...@gmail.com On 23 June 2015 at 05:02, Attila Kinali att...@kinali.ch wrote: Hi, I was looking up some stuff and realized (again) that I don't know anything about how magnetic electronic components (inductors/solenoids, transfomers, baluns, ferrite beads...) work. Yes, I can calculate the inductance, I know how to get from the AL value to number of windings. But I don't know anything about the practical issues or where they come from. Unfortunatelly, this knowledge seems to generally rare among EEs (at least everyone I asked in the last couple of years) and books about it are either long out of print (with no pdf available) or more geared towards the physics student. So, does anyone have any recomendation where I could read up on this? Books, pdfs, webpages,... anything. Also something that covers more the application side, ie how to use ferrite beads/toroids to build devices, would be appreciated. Thanks in advance Attila Kinali -- I must not become metastable. Metastability is the mind-killer. Metastability is the little-death that brings total obliteration. I will face my metastability. I will permit it to pass over me and through me. And when it has gone past I will turn the inner eye to see its path. Where the metastability has gone there will be nothing. Only I will remain. ___ 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] Thunderbolt/Arduino RS232 Interface Issue
You have TX connected to TX? Swap your TX/RX connections and see if the levels improve. Tom Harris celephi...@gmail.com On 3 June 2015 at 14:38, Dan Quigley d...@quigleys.us wrote: Hello, I'm integrating an Arduino (Due/Mega have tried both) with a surplus Thunderbolt and need some advice. The Thunderbolt is a known working unit (supplies 10Mhz to my HPSDR rig) and the serial interface works fine between it and a PC. I've read the coverage about this kind of integration (and some of the archived discussions on this board) and am employing a commercially available MAX232-based shield (RS232 V2) to handle the level translations. Just three lines (RX/TX/GND) are used. The MAX232 circuit is working, reliably passing data between the Arduino and a PC. With the Thunderbolt is connected to the MAX232 no data passes. Activity LEDs on the non-RS232 of the MAX232 circuit show no activity when the Thunderbolt is providing data, indicating the MAX232 is not performing the intended level translation. I've scoped the RX/TX lines coming from the Thunderbolt both when connected to the Arduino and not. There is a distinct difference. When disconnected, the pulses are about 10.3v and nice, crisp and square. Connected, the pulses are ~50% lower in voltage (4.1v) showing an exponential rise in voltage and trace noise. I'm pretty much stumped at the moment and wonder if anyone can offer a suggestion or thoughts on a direction to take. Thanks in advance, Dan Quigley (N7HQ) ___ 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] Greek clocks - planets rather than seconds
Good question. I intrigued me so I researched it. To make gears the Greek craftsmen made a circular blank, then marked it out for the correct number of teeth, probably using dividers, then filed the teeth with a triangular needle file Analysis of the Antikythera Mechanism shows the sort of irregularities that this method would give, Michael Wright made gears this way to prove it. The teeth have a 60 degree angle and are triangular in profile, which is not very efficient, but good enough for a clock. I made a pair of gears this way, it took half a day but it worked. Thanks for the link. Tom Harris celephi...@gmail.com On 11 May 2015 at 10:32, Hal Murray hmur...@megapathdsl.net wrote: Michael Wright talking about the Antikythera http://www.the-eg.com/videos/michael-wright-antikythera-resurrector-eg8 The video is 1/2 hour. I thought it was good. He's a colorful speaker. Anybody know how they made gears back then? Or machinery in general? What did they use for a file? How did they make files? The Computer History Museum is having an event: May 13, 2015 10:30 AM Secrets of the Antikythera Mechanism http://www.computerhistory.org/events/upcoming/ In 1900, sponge divers off the coast of the tiny Greek island of Antikythera made an astonishing discovery: the wreck of an ancient Roman ship lay 200 feet beneath the water, its dazzling cargo spread out over the ocean floor. Among the life-size statues and amphorae was an encrusted piece of metal, which after nearly a century of investigation, is finally revealing its secrets -- These are my opinions. I hate spam. ___ 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] Another Philipe Patek clock
I do odd jobs for a real clockmaker who does the contracts no-one else wants. Like the clocks on the main entrance of Melbourne's Flinders Street Station that indicate the leaving times for all the lines. Anyway I spotted this old master clock in the store. I bet it looks even more beautiful inside. It has quartz in big letters on the front. That dates it back to when quartz signified quality and accuracy. Maybe I should make an offer. Image resize to something sensible, thanks for the nod TvB:) Tom Harris celephi...@gmail.com ___ 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] Another Philipe Patek clock
I can open it up whatever. I shall certainly take photos. I hope that it did not have internal nicads, as they will indeed be in a sad state after 30 years :( Tom Harris celephi...@gmail.com On 31 March 2015 at 01:31, paul swed paulsw...@gmail.com wrote: You should make an offer that way we all get to see the insides. The movement seems to have value no matter what. You may indeed open up to find the magical batteries have turned to white powder. Most clocks like this either had internal or external battery sets. Very nice indeed. Regards Paul WB8TSL On Mon, Mar 30, 2015 at 5:13 AM, Tom Harris celephi...@gmail.com wrote: I do odd jobs for a real clockmaker who does the contracts no-one else wants. Like the clocks on the main entrance of Melbourne's Flinders Street Station that indicate the leaving times for all the lines. Anyway I spotted this old master clock in the store. I bet it looks even more beautiful inside. It has quartz in big letters on the front. That dates it back to when quartz signified quality and accuracy. Maybe I should make an offer. Image resize to something sensible, thanks for the nod TvB:) Tom Harris celephi...@gmail.com ___ 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] serial parsing program
Python has a nice library struct that can take a binary buffer of just about anything, integers, strings, etc, with any alignment or byte ordering and parse it to a list of values. I've never had the need to use anything else. Perl probably has the same as well. Tom Harris celephi...@gmail.com On 25 March 2015 at 11:37, Bob Stewart b...@evoria.net wrote: Hi Cash, Have you looked at the sourcecode for the gpsd package? packet.c would probably be your starting point. The gpsd package parses pretty much every gps receiver. I'm not sure if this is what you're looking for, or if you specifically want something high-level. Bob From: Cash Olsen radio.kd5...@gmail.com To: time-nuts@febo.com Sent: Tuesday, March 24, 2015 5:22 PM Subject: [time-nuts] serial parsing program I'd like to find a program that has a very flexible serial input and can be easily setup to parse a binary sentence. Specifically, U-Blox timing but more general purpose would be nice for future projects. Has to be able to handle 1, 2, and 4 byte fields, and checksums would be nice also. Should run on Windows for the immediate project but Linux for next projects. -- S. Cash Olsen KD5SSJ ARRL Technical Specialist ___ 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] Greenwich Timekeeping
The public exhibition for this conference Ships, Clocks and Stars: The Quest for Longitude is apparently coming to the colonies (Canada Australia) this year, so us colonials might get a chance to feast on the Harrison timepieces in all their glory. True clock p**n. Tom Harris celephi...@gmail.com On 26 March 2015 at 03:27, Tom Van Baak t...@leapsecond.com wrote: For those of you near London with an interest in Greenwich, Harrison, and pendulum clocks there's an event on April 18 that might be worth your time. Harrison Decoded: Towards a Perfect Pendulum Clock http://www.rmg.co.uk/whats-on/events/harrison-decoded http://www.rmg.co.uk/sites/default/files/harrison_decoded_draft_programme_250215-3.pdf /tvb ___ 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] Obscure HP T/F instruments in ebay.fr
What beautiful looking instruments. I bet they look just as sexy from behind. Someone should make a coffee table book of glamour shots of old HP gear. I'd buy a copy. Including a gatefold of a full rack, captioned Nice rack Tom Harris celephi...@gmail.com On 19 March 2015 at 06:57, Poul-Henning Kamp p...@phk.freebsd.dk wrote: There is a seller on the french eBay which has some rather old/obscure HP T/F instruments up cheap: 281603533317 HP K05 5060A Linear Phase Detector 281607493683 HP J19 59992A HP5371A Demonstrator 311298011221 HP 8709A Synchronizer 311307909618 HP 101A 1 MC Highly Stable Quartz Oscillator Reference 311307936107 HP 5275 Time Interval Counter There may be more... -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@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. ___ 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] Simple AC mains zero-cross detector
I actually needed to do real ZCD for thyristor switching off incredibly noisy bad AC suppplies used down mines in third world countries. I used a digital PLL to lock to the AC line volts waveform with a simple detector with a threshold of 50V set by a zener driving an opto. I think the loop time constant was set very slow, several seconds as the AC came from a gererator so very slow to change as you have the inertia of the massive armature in the generator. Logging this over several days on the mains network showed it slowing slightly during the day and then speeding up at night to give the right number of cycles per day. It was insensitive to voltage. We did find that isolating the zener opto via a transformer gave a temperature dependant phase shift, exactly what you don't want for switching thyristors. Tom Harris celephi...@gmail.com On 19 December 2014 at 08:16, Charles Steinmetz csteinm...@yandex.com wrote: Gary n...@lazygranch.com wrote: Why not use a lower voltage transformer, preferably not at a lethal voltage. You only need a couple of volts to drive the rest of the circuit. As you can see from the schematic, the voltage is diode-clamped almost immediately to ~ +/- 1.5v. The reason for using a 120v winding is to take advantage of the free slope enhancement provided by the higher voltage. The 120v winding provides a signal with a zero-cross slew rate of ~65mV/uS. A 12v winding would slew only ~6.5mV/uS. The faster the slew rate, the more accurately one can locate the zero crossings. If you are going to look at glitches, that should be done by sampling the AC (transformer coupled obviously). Basically the circuit to detect period is dedicated to that function. Since the frequency won't vary significantly, a high order filter wouldn't be an issue, as long as you don't care about delay. You are suggesting two separate data collections, one geared toward grid frequency and one geared toward glitch detection. That's fine, and might be preferable if it provided better results than using just one data collection. But using a higher-order hardware filter does not provide better frequency determination than post-processing the ZCD data. The circuit presented allows one data collection to do both functions well. It has enough filtering to prevent local interference from corrupting the data, it can locate 60Hz zero crossings to within 1uS (i.e., frequency resolution significantly better than 0.01 Hz, single-shot, which can be filtered/averaged to get whatever resolution you want in post-processing), and it can locate transient events to within 1uS. Win-win. Best regards, Charles ___ 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] GSM/GPRS module timing accuracy
How are you getting time from the GSM network? If you are using the NITZ (look it up) service then you can use an unactivated SIM for free, but the accuracy is woeful, it can be seconds out. Else you will have to have a live SIM and use NTP to a server. If you make any progress please post to the list. I have not heard of being able to access the clock in the tower over the network. The beauty of phone network is that it works in buildings, where GPS does not reach. Tom Harris celephi...@gmail.com On 12 November 2014 01:24, Tony tn...@toneh.demon.co.uk wrote: How accurately can you set, and keep in sync a local clock (in the UK) by getting timing from a cellular network using a very low cost GSM/GPRS modem module such as a SIM900? Is it possible to get better than hundreds of microseconds for example, perhaps even a few tens of us? How frequently can the clock be synced (to avoid having to have a high performance local clock) and would it incur network charges? Does it depend mostly on the network, the module, location or the algorithms employed? I am thinking of a fixed location application but presumably couldn't guarantee that connections will always be to the same base station so is it possible to estimate the distance to the base station to compensate for the time of flight of the radio signal? I guess it should be possible to read the signal strength from the radio module to get a crude estimate. It should be obvious that I know next to nothing about GSM standards other than that the base stations have access to a high quality clock. If its not possible to do this reliably, are their any low cost ( $20) combined GSM/GPRS + GPS modules which provide timing accurate to a few 10s of us or so? Thanks Tony H ___ 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] GSM/GPRS module timing accuracy
I am in Australia and the accuracy of the NITZ service can be slow by up to 15 SECONDS. I have no idea why it is so bad. You can try this for yourself. Just get a GSM modem connected to your laptop, set it up to accept NITZ updates and print the results on the serial port, and take a drive around your neighbourhood. As you go between towers you will get new NITZ updates, and you can log the accuracy. Try not to get arrested as a terrorist :) There is a simplified NTP service that only receives a small packet, I think I saw an example for Arduino. Tom Harris celephi...@gmail.com On 12 November 2014 09:34, Tony tn...@toneh.demon.co.uk wrote: On 11/11/2014 21:52, Tom Harris wrote: How are you getting time from the GSM network? If you are using the NITZ (look it up) service then you can use an unactivated SIM for free, but the accuracy is woeful, it can be seconds out. I'm not at the moment; mobile phones do set their clocks from the network but I've no idea how accurately it can be done - which is why I was asking. Else you will have to have a live SIM and use NTP to a server. If you make any progress please post to the list. I have not heard of being able to access the clock in the tower over the network. The beauty of phone network is that it works in buildings, where GPS does not reach. Tom Harris celephi...@gmail.com I would have a live SIM as the modem would be used periodically (but not necessarily frequently - perhaps every 24 hours or more) to send data. I would not want to use an NTP service as I would only have a micro-controller with limited memory. Tony H ___ 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] Worlds first time code generator and ultimate decoder
If your fingers ain't purple, you ain't doin' science... A blast from the past, when the output was recorded as a line on paper. I remember those recorders with pens that had to be filled from a bottle of ink, purple and green were popular colours, and both stained your fingers. As a bonus it was easy to perform integrations of the output over time. Simply cut the roll along the recorded line and weigh the remainder on an analytical balance, the ratio of the weight to an equal length of uncut roll was the integral. What larks! Tom Harris celephi...@gmail.com On 12 August 2014 04:31, Don Latham d...@montana.com wrote: So who could afford Brush paper? I had hundreds of feet of adding machine paper (cheap!) If your fingers ain't purple, you ain't doin' science... Don Chuck Harris It only appeared that way if you were using the wrong paper for the chart recorder. Those that had needles that moved in an arc also had chart paper that was ruled using lines in the T axis, and arcs in the X axis. -Chuck Harris Max Robinson wrote: The issue of the recording stylus apparently moving backward along the time axis shouldn't be a mystery to anyone who remembers the old Brush (brand name) galvanic chart recorders. The pen tip moved in an arc rather than rectilinear and for slow paper movement the graph appeared to move backward in time. I have no idea exactly how virtual stylus works in decoding these recordings but it seems possible that they could account for the recording stylus being moved in an arc rather than a straight line. Regards. Max. K 4 O DS. ___ 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. -- The power of accurate observation is commonly called cynicism by those who have not got it. -George Bernard Shaw Dr. Don Latham AJ7LL Six Mile Systems LLC 17850 Six Mile Road Huson, MT, 59846 mail: POBox 404 Frenchtown MT 59834-0404 VOX 406-626-4304 Skype: buffler2 www.lightningforensics.com www.sixmilesystems.com ___ 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] First success with very simple, very low cost GPSDO, under $8
Tom Harris celephi...@gmail.com On 10 April 2014 16:35, Chris Albertson albertson.ch...@gmail.com wrote: To many ifs and you could The Arduino is what it is. There is no capture register, no interrupt priorities and the counter is... There certainly is an input capture, and it makes the code EASIER to understand, as you know that the timer will be captured on the next cycle after the PPS edge, not when the current instruction has finished and the time 1 overflow interrupt has exited (forgot about that one). This forum post should get you started. Sure the Arduino is a prettly limited processor but it is more than enough for this job. ___ 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] First success with very simple, very low cost GPSDO, under $8
Another point with the software is that your handler for the PPS just reads the counter. This gives an offset between the PPS edge and the value read, as your software takes time to respond to the interrupt and read the counter. In your code, it doesn't matter as you only have one interrupt. However, if you have another interrupt enabled, this could run after the PPS pulse but before the handler runs, giving you a very rare jitter. A better way would be to use the input capture feature to read the timer into a capture register. Then the interrupt handler has until the next edge to read the capture register. Just an idea, you might be able to assign the interrupt priority for the PPS edge to a priority above all others to avoid this problem, but this is getting complex. Simpler to handle it by hardware. To debug jitter, you could make your mainline set an output line, and watch the delay between the PPS and the line on a CRO set on infinite persistance, just to check if it works. Tom Harris celephi...@gmail.com On 9 April 2014 13:05, Chris Albertson albertson.ch...@gmail.com wrote: I just had some success with a new GPSDO based very much on Lars Walenius' design I cut his design and his software down to make it even more simple and cost less. The controller is now well under $8. The software is also much simpler and easy to read even if you are not a software guy. Lars' design and software will out perform mine. There is no question on that. But my goal was to first build a VERY low cost and more importantly easy to understand and replicate GPSDO. In this first version of the GPSDO I did not implement the TIC. I only count how many cycles occur from the local oscillator between PPS pulses and then use a PI control to adjust the DAC. Performance. I am open to suggestions on how I can characterize the performance. This project is being designed for a beginner who would not have exotic test equipment. I would call the performance not as bad as you might guess. I have had the output of this GSPDP and the 10MHz signal from a Trimble Thunderbolt both up on my Tek 365 100MHz dual channel scope for about 26 hours and they seem to more or less keep in phase. The GPSDO waveform drifts one way then the other. I can see the short term stability is good only to about the E-9 level but of course being locked to a GPS it has very good long term stability. And this with about $8 worth of parts and build in about one hour. (Not counting the power supply (a plug-in wall wort type), OCXO and GPS) Also the controller software is intentionally simplified. The E-9 is an estimate. I'm looking for a good way to measure it with simple tools. Plans: I will add features and sophistication one step at a time and I will try to document the process. Even as I add more my goal is still (1) an understandable design that anyone can build with no special tools or equipment and (2) cost. With equal importance to each. The next step is too add some refinements to the software, different modes and so one. But this stripped down version will be the introduction for a tutorial on GPSDO design. Goals: I want to document this as a design others can build. Even if they are new to all of this. I also want to keep the software open and easy to modify in the hope that others will actually modify it and post their mods here for kind of peer review Parts list: 74HC390, Aruindo pro mini, two small electrolytic caps and three resisters. That's it. The Mini is $3.71 with free shipping the 74hc390 was $1. Other parts where in the junk box. A software listing is attached. I used some of Lars' code but added a few ideas of my own and removed 80% of the functionality in preference to clarity. I'm not 100% done. I know I can make if more readable. -- Chris Albertson Redondo Beach, California ___ 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] Frequency Counter using OCXO and MCU
Tom Harris celephi...@gmail.com On 13 March 2014 01:21, Chris Albertson albertson.ch...@gmail.com wrote: Sorry forgot to add this. As for delayed turn on. That can work but why not simply have the software go into a 5 or 10 second wait before it does anything else. Display warming up or please wait on the LCD. Never present the customer with this sort of message. Something like optimising settings or contacting boot sever... OK. Makes them think that they have got value for money. ___ 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] Different breed of time nuttery
The really scary thing is that this is some sort of postgraduate thesis project examined by a swag of learned doctors, complete with the artistic waffle of What It All Means. Tom Harris celephi...@gmail.com On 24 February 2014 15:11, Daniel Mendes dmend...@gmail.com wrote: This is a different breed of time nuttery than usual in this list but i think that at least some of you will enjoy it: http://www.behance.net/gallery/FLUX-1440/2420150 Found it at hack a day 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] How I got my FE-5680A to lock in Sydney, Australia
I got into trouble once when we got a centrifuge from the US (I'm in Australia) and it didn't work and I suggested to the Yanks that they should have made it revolve in the opposite direction for working S on the equator. The idiots tried this by rewiring the motor and the basket (the large heavy casting that holds stuff to be centrifuged) promply unscrewed itself and nearly came off the shaft. 30Kg of steel about 500mm in diameter spinning at 5000rpm careening round the lab would not be much fun. I never thought that there could actually be a real reason why things stuff up across the equator. Actually the vertical component of the magnetic field here has the opposite sense, which is why compasses made for Europe are unusable in Australia, the card just tries to align itself at 45 deg to the horizontal and refuses to work as it fouls the internals of the mount, so this might make sense. Tom Harris celephi...@gmail.com On 7 February 2014 08:32, Jamieson (Jim) Rowe jimr...@optusnet.com.auwrote: Hi again folks, You may (or may not) recall that a month or so ago, I asked for any information that might be available regarding how to fix a 'used' FE-5680A rubidium module from China (via ebay) which was tested by the supplier in China as working OK, but would not seem to lock up to rubidium here in Sydney. There wasn't a great deal of info available, it seems, so I kept on checking ideas myself - mostly with no luck. The module would never lock, but kept cycling back and forth between about 9.999770MHz and 10.36MHz - 'searching' for a lock, but never finding it. Anyway, a couple of days ago I was reading more about the operation of rubidium vapour oscillators, and noticed that the 'filter cell' is very sensitive to magnetic fields - hence the mu-metal shielding case, and also for the 'C-tuning' coil. And I wondered if the main reason why the FE-5680A had apparently worked in China, but wouldn't lock up in Sydney (Australia) might be caused by the fact that Quangzhou (China) is in the northern hemisphere while I'm 'down under' in the southern hemisphere - where the earth's field is presumably somewhat different, in terms of both strength and direction. So I decided to test this in a crude way, by inverting the FE-5680A and seeing what happened. And - lo and behold - it locked up within 2.5 minutes, and stayed locked until I turned off the power and let it go cold again. The next morning I applied power again, and within 3 minutes it locked up again with no problems. And it's been locked up now for over 48 hours... So it seems that the different magnetic field here may have been the problem - either that, or it may have received a 'jolt' in transit, which prevented in from locking unless it was inverted. But how do I tell which of these explanations is right, without 'opening her up' again and looking for some kind of subtle physical fault? Another idea: perhaps the mu-metal shield case had acquired a small dose of magnetisation in transit (via a physical shock, or from a strong field metal detector). I guess in this case that I would have to remove the two halves of the case, and bake them in a furnace to demagnetise them again. Or should I just run the FE-5680A upside down permanently - the simple but 'crude' answer? I'm not sure if this FE-5680A has the 'C-tuning' gizmo fitted, or wired up. Am I right in thinking that another approach might be to try varying the tuning via the RS-232C serial port? Does this work via the C-tuning coil anyway, or by tweaking the DDS? I hope a much more experienced time nut can provide a few answers, please. Jim Rowe ___ 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] 60 Hz power glitch, US West coast (Silicon Valley)
For your setup measuring mains there will be a large phase difference across the transformer. This is due to very many physical properties of the materials, the largest being the magnetic succeptability of the core. Now, this does show a slight temperature dependance. So how do you know that you are not getting a slow variation in the phase showing up as a frequency shift, since you are measuring such tiny variations. I know that the transformer is probably in thermal equilibrium with it's surroundings, so is at a steady temperature, but this problem (of getting an accurate idea of mains frequency phase) has exercised me over the years. I currently use an opto and voltage reference to get mains frequency, phase and voltage (computed by lookup table from pulse width) which I found was more stable than a transformer. And cheaper as well, since this is for a commercial product. I'm just surprised that you get such results with a cheap transformer. Just remembered, we got a tiny change in phase shift across a transformer due to its orientation, we could turn it 90 Deg and get a tiny change (less than a milliradian), we never got to the bottom of it, maybe the Earth's magnetic field? Tom Harris celephi...@gmail.com On 6 February 2014 04:39, Hal Murray hmur...@megapathdsl.net wrote: jimmydb...@gmail.com said: Interesting.. I'm assuming the green graph is actual voltage and the red graph is..? The green is the frequency as measured over the last 10 seconds. The red is the long term clock offset in cycles relative to what it would be if the frequency was exactly 60 Hz. It's the error you would see if you looked at a clock that was tracking the power line. The 0 point is arbitrary since I can't see the reference clock the power system is using. For those graphs, I used the start of the day/file as 0. I've never done any mains monitoring/measuring and was wondering, what's your equipment setup? It's simple. The hardware is an AC wall wart and a couple of resistors as a divider connected to a modem control pin. I forget which one. It's the one that ntpd expects to use with a PPS input. There was a discussion on that topic here a year or 3 ago. It's in the archives, but I couldn't find it with a quick look. The software is a simple python hack. It runs on Linux. http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/pps.py Linux has a back door to the PPS info. Things like /sys/class/pps/pps0/assert give text like this: 1391619268.25084#1125070 The number left of the # is the time of the last PPS. The number to the right is the pulse count. The software above just waits 10 seconds, grabs another sample, and writes a line of text to a log file and switches to a new file every day. It's 1/2 megabyte per day. If you have FreeBSD or NetBSD rather than Linux, it shouldn't be too hard to use the same API as ntpd uses. I don't know how PPS works on Windows. Another approach would be to feed it into the audio input and scan for zero crossings. I captured the raw binary for a while when I was chasing some noise glitches. It's a lot of data. -- These are my opinions. I hate spam. ___ 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] more solar clock stuff
Tim Hunkin has made a similar clock, see http://www.timhunkin.com/27_domestic_clocks.htm The elephant clock down the bottom of the page indicates the moon's phase in a very innovative way. Mind you the night day sectors are equal, so they are for the equator, not for the maker's lattitude of 50 deg :) Tom Harris celephi...@gmail.com On 21 January 2014 05:49, Jim Lux jim...@earthlink.net wrote: So here's my next idea.. Set up a 24 hour movement (no minute hand) so that you have the sun moving around the dial: at the top at solar noon, with the rate being reasonably constant around the dial(e.g. using the solar clock algorithms developed) Then, have two other pointers or sectored disks on the face to indicate sunrise and sunset time. I haven't figured out the mechanical aspects, but maybe a small motor driving the edge of a clear plastic disk. (or if there were a good cheapish source for multi axis pointer systems). One could also add a moon pointer (and all the rest of the planets too). Sort of a geocentric Orrery. The planets would need to be able run in both directions to accommodate retrograde apparent motion. It would be easy with laser pointers or light beams and stepper motors driving a tilted mirror to project moving dots on the wall, but a more mechanical display would look nicer, I think. Once the mechanical aspect is figured out, the software should be fairly straightforward to drive whatever motors there are. (After noticing Saturn this morning when I went to go get the paper before dawn) ___ 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] Shortt Clock Recent Measurements
The eccentric English physicist Boys made quartz fibres by attaching one end to a crossbow bolt, heating the middle and then firing the bolt, at what I have been unable to determine. He used this to measure the gravitational constant by suspending iron spheres from the resultant fibre, which of course was amazingly strong for it's diameter. Myself I'd use a pneumatic cannon, since I have one, rather than a crossbow. Tom Harris celephi...@gmail.com On 11 December 2013 15:55, Jim Lux jim...@earthlink.net wrote: On 12/10/13 5:57 PM, Don Latham wrote: I always thought invar was the magic metal. Quartz rod? You can get those at some reasonable cost? 12 mm dia fused qtz, about $10 per ft, so under $40 to get going, assuming 4 or 5 to learn how to do it right. It does break... 12.7 mm dia Invar 1 m long is $530 Amazing, and quartz is better (A single crystal would cost a pretty penny. I'm not sure a crystal that long can be drawn using a zone furnace). Pyrex is also available. These are quick 'net prices. John Strong's book tells how to make thin high-q fused silica fibers with an appropriate burner. Just the thing for your torsion balance, etc. back in the day when a self respecting experimental physicist built their own equipment. ___ 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] Shortt Clock Recent Measurements
There is a good writeup of the Dicke switch in Horowitz Hill The Art of Electronics, since Horiwitz is a radioastronomer of note. I've just bought my daughter a copy for Xmas, poor girl, she wants to be an engineer... Tom Harris celephi...@gmail.com On 11 December 2013 13:02, Don Latham d...@montana.com wrote: Brooke Clarke PS When I was working in microwave electronics we talked about the Dicke radiometer, but I haven't found any definitive web page about that. Gotta look at Radio Astronomy pages and history. Actually, Dicke was using that radiometer to look for the microwave cosmic background, but the bell Labs guys had the big antenna. size matters :-) -- The power of accurate observation is commonly called cynicism by those who have not got it. -George Bernard Shaw Dr. Don Latham AJ7LL Six Mile Systems LLC 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 Skype: buffler2 www.lightningforensics.com www.sixmilesystems.com ___ 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] Shortt Clock Recent Measurements
It's in the section on lock in amplifiers I think. The switch has a clever 3 way action I think but I can't quire remember how it works. I do remember thinking how ingenious it was at the time, since I was designing lock in amplifiers for detecting optical absorbance over 10cm path lengths using photodiodes, instead of the tradional PMTs. Tom Harris celephi...@gmail.com On 13 December 2013 14:19, Brooke Clarke bro...@pacific.net wrote: :Hi Tom: I can't find anything in the Table of Contents or in the index. Can you tell me the page or title of the writeup? Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html Tom Harris wrote: There is a good writeup of the Dicke switch in Horowitz Hill The Art of Electronics, since Horiwitz is a radioastronomer of note. I've just bought my daughter a copy for Xmas, poor girl, she wants to be an engineer... Tom Harris celephi...@gmail.com On 11 December 2013 13:02, Don Latham d...@montana.com wrote: Brooke Clarke PS When I was working in microwave electronics we talked about the Dicke radiometer, but I haven't found any definitive web page about that. Gotta look at Radio Astronomy pages and history. Actually, Dicke was using that radiometer to look for the microwave cosmic background, but the bell Labs guys had the big antenna. size matters :-) -- The power of accurate observation is commonly called cynicism by those who have not got it. -George Bernard Shaw Dr. Don Latham AJ7LL Six Mile Systems LLC 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 Skype: buffler2 www.lightningforensics.com www.sixmilesystems.com ___ 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] NITZ Timestamps
Here's a general question about the NITZ timestamp that is sent by the phone tower when your mobile connects to it. Why are they so far off from the actual time? I have seen offsets up to 15 seconds behind, mind you this was from a tower in the bush, city towers are usually only 2 secs behind. Tom Harris celephi...@gmail.com ___ 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] GPS locked 60Hz?
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Tom Harris celephi...@gmail.com ___ 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] [OT} audiophile outlets.....
From A Song of Reproduction by Michael Flanders Donald Swann: All the highest notes neither sharp nor flat, The ear can't hear as high as that. Still, I ought to please any passing bat, With my high fidelity. From the LP At the Drop of a HAT, which is so old that the artists note that it was being recorded in STEREO, in 1957 or so. Good to see that audiophiles are not a new phenomenon! If you haven't heard of Flanders Swann they perpetrated the song with the lyric Mud, mud, glorious mud... On 20 June 2013 16:18, John Marvin jm-t...@themarvins.org wrote: Actually, Audiophools don't care about 44.1Khz anymore. They care about 96, 192 and even 384 Khz sampling rates. John On 6/19/2013 10:09 PM, Chris Albertson wrote: On Wed, Jun 19, 2013 at 5:54 PM, Tom Knox act...@hotmail.com wrote: I wonder what is the best way to obtain 44.1KHz from a 5-10MHz reference. (10,000,000 / 100,000 ) * 3 * 147 = 44.1K These are PPL chips that can do this. change 147 to 160 and you can clock the 48K rate for video. I hope I got the numbers right. __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Tom Harris celephi...@gmail.com ___ 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] An embedded NTP server
+1 for Forth! +1 for your opinions on PICs AVRs. We can buy low end NXP ARM Cortex M0 chips (e.g. LPC1113) for less than the PIC18 we were using before, and it has a real compiler and (unlike the real world) evidence of intelligent design! Do you really need an OS? Surely for a box that is only ever going to be an NTP server you just need a network interface and good maths? I've just seen a later comment where you mention floating point support, but would 64 bit integer maths work just as well? On 3 January 2013 06:25, Chris Albertson albertson.ch...@gmail.com wrote: On Wed, Jan 2, 2013 at 11:16 AM, Poul-Henning Kamp p...@phk.freebsd.dk wrote: I've given up on PIC and Atmel microcontrollers and their antiquated CPU designs. My life is too short to fight odd-ball compilers, when I can get a real 32 bit CPU and a good compiler instead. That is a valid point if you are building a one-off project. Your time is worth something. But if you plan to sell a million AA cell battery chargers using a 32-bit controller is uneconomical. These will always be a bigger market for 8-bit chips then for 32-bit chips. For an NTP server I'd go with something that can run an OS and the NTP reverence implementation. ARM (and others) can do that. -- Chris Albertson Redondo Beach, California ___ 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. -- Tom Harris celephi...@gmail.com ___ 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] Is there anything wrong with DCF77?
If you can look at the output of a DCF77 demodulator you should see a nice clean set of 100ms/200ms pulses every second. All you need is a CRO, or you could just use a LED to indicate the state. On 2 January 2013 01:00, George Race geo...@mrrace.com wrote: Hi Anthony, is there any possibility that you have a source of local interference that started up in your home or area? From time to time, I have had everything from power line arcing noise to a new computer power supply that was generating a high level of interference blocking signals on different frequencies. If you have a spectrum analyzer available that will cover the frequency range of DCF77, it may not hurt to look around and see what you can find. George -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Anthony G. Atkielski Sent: Tuesday, January 01, 2013 7:40 AM To: time-nuts@febo.com Subject: [time-nuts] Is there anything wrong with DCF77? For the past several days (now thirty hours straight), none of my radio-synchronized clocks has been able to synchronize with DCF77. Is there a problem with the transmitter, or maybe a geomagnetic storm or something that could explain it? I've been looked at the transmitter Web site and searching for news and information on any disturbances that would affect reception, but I haven't found anything. I'm about 500 km from the station. The only thing I have that will sync is my wristwatch, and it will only do it if I stand outside in an open area. -- Anthony ___ 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. -- Tom Harris celephi...@gmail.com ___ 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] 2.5 Ghz 12 digit counter project
Watch out for Silicon Chip designs, they have a habit of not making the source code available, which you only find out at the end of the project. I suppose that it is to allow the author to make a few extra $$ selling programmed micros. They had a nice 3 phase inverter design a year ago that had this problem, I wrote to the author promising not to distribute the source, I just wanted to read it, but didn't even get the courtesy of an answer. I suspect that this counter is like the inverter, an oldish design that is not worth building as you can get the same for half the cost out of China. What makes it worthwhile is getting the hardware the source code, so that you can tinker with it. Actually I had a look at the counter and it looks similar to the 8 digit designs using the Intersil 7217 IC from the 80's. Gripe ends. On 28 December 2012 06:12, Paul Amaranth p...@auroragrp.com wrote: Did anyone see the article in the December Silicon Chips magazine about building a 12 digit 2.5 GHz counter? It has an option for a GPS 1pps input so you could have some expectation that the last couple of digits mean something. The website only has the article cover page in pretty much unreadable type. -- Paul Amaranth, GCIH | Rochester MI, USA Aurora Group, Inc. | Security, Systems Software p...@auroragrp.com | Unix Windows ___ 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. -- Tom Harris celephi...@gmail.com ___ 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] Strange DCF77 master clock data
I am logging the data from this strange master clock, and the none of the bits 42 through 44 are stuck. Good idea, though. I have just checked tonight, and the DOW is indicating as 5 (Friday), despite it only being Monday. Good idea though. On 9 December 2012 23:24, mike cook mc235...@gmail.com wrote: Le 09/12/2012 11:28, Tom Harris a écrit : Greetings Time Nuts. Time related, but unusually so: I am examining the DCF77 (see http://en.wikipedia.org/wiki/**DCF77http://en.wikipedia.org/wiki/DCF77for a refresher) data output from a master clock intended to drive a series of slave clocks operated from 24V DC, interrupted by 100ms or 200ms pulses to signal '0' '1' on the data. What I am seeing is that the day of week bits 42 through 44 inclusive do not code the day correctly, they seems to have a variable offset from the actual day, I have seen an offset from +1 to +3. The rest of the data, ncluding parity bits, are OK. Today, 9/12/2012, the day is Sunday, which should be coded as '7'. However I am seeing a value of '3', which is Wednesday. Is this normal, do wired DCF77 slave clocks transmit munged dow data to prevent them being used with someone else's master clock? If they do I am hosed since I am trying to reverse engineer the master clock. Is it just bit 44 being stuck on zero? or can each dow get varying values? -- Les chiens aboient, et la caravane passe. __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Tom Harris celephi...@gmail.com ___ 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] Strange DCF77 master clock data
That's the funny thing, the parity bit is correct for the value of DOW, just that the DOW value is wrong. On 9 December 2012 23:27, Azelio Boriani azelio.bori...@screen.it wrote: Is the parity bit P3 consistent? It protects the day of the month and that of the week. On Sun, Dec 9, 2012 at 1:24 PM, mike cook mc235...@gmail.com wrote: Le 09/12/2012 11:28, Tom Harris a écrit : Greetings Time Nuts. Time related, but unusually so: I am examining the DCF77 (see http://en.wikipedia.org/wiki/DCF77 for a refresher) data output from a master clock intended to drive a series of slave clocks operated from 24V DC, interrupted by 100ms or 200ms pulses to signal '0' '1' on the data. What I am seeing is that the day of week bits 42 through 44 inclusive do not code the day correctly, they seems to have a variable offset from the actual day, I have seen an offset from +1 to +3. The rest of the data, ncluding parity bits, are OK. Today, 9/12/2012, the day is Sunday, which should be coded as '7'. However I am seeing a value of '3', which is Wednesday. Is this normal, do wired DCF77 slave clocks transmit munged dow data to prevent them being used with someone else's master clock? If they do I am hosed since I am trying to reverse engineer the master clock. Is it just bit 44 being stuck on zero? or can each dow get varying values? -- Les chiens aboient, et la caravane passe. ___ 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. -- Tom Harris celephi...@gmail.com ___ 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] Strange DCF77 master clock data
Greetings Time Nuts. Time related, but unusually so: I am examining the DCF77 (see http://en.wikipedia.org/wiki/DCF77 for a refresher) data output from a master clock intended to drive a series of slave clocks operated from 24V DC, interrupted by 100ms or 200ms pulses to signal '0' '1' on the data. What I am seeing is that the day of week bits 42 through 44 inclusive do not code the day correctly, they seems to have a variable offset from the actual day, I have seen an offset from +1 to +3. The rest of the data, ncluding parity bits, are OK. Today, 9/12/2012, the day is Sunday, which should be coded as '7'. However I am seeing a value of '3', which is Wednesday. Is this normal, do wired DCF77 slave clocks transmit munged dow data to prevent them being used with someone else's master clock? If they do I am hosed since I am trying to reverse engineer the master clock. -- Tom Harris celephi...@gmail.com ___ 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] GPS Modules Indoors
Greetings I know that the accuracy of GPS degrades indoors. However, suppose that I just want to turn a GPS module on, acquire the current time accurate to a second, and then turn it off. I can get a good deal on the U-Blox LEA-5H modules (same as used on Arduino shields I think), which have a high sensitivity, and I can use an active antenna if needed. Am I wasting my time. Sorry for not requiring the time more accurate than a second, but that's all the clients require. -- Tom Harris celephi...@gmail.com ___ 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] Disciplining a TCXO
Greetings, I have been asked the viability of using a vanilla TCXO, with an accuracy of +/- 0.5ppm (+/- 15 secs per year) that is disciplined occasionally (perhaps only once a month) with a GPS module. The application is for an analogue clock, which powers up a GPS module every so often to learn the drift characteristics of the TCXO, which it then compensates to generate indicated time. The TCXO's that I have played with have a very predictable aging characteristic over time, at least in a normal home/office environment. -- Tom Harris celephi...@gmail.com ___ 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] OT question about liquid cooling
My day job is large industrial power supplies. The test racks have large resistive loads with big fans exhausting to the outside. Cheap simple. Safety is by several strings of temperature cutouts wired in series. We usually get work experience students in to wire them up. Tip: to make a funny valued power resistor, just get the next value up and wrap some nichrome wire around it to bring it down to the correct value. I met an engineer who made a battery charger for one of our submarines. This was tested by putting the load bank in a dumpmaster, and keeping it filled up with water using a firehose! On 4 October 2012 02:01, Javier Herrero jherr...@hvsistemas.es wrote: Hello all, Please excuse me for the OT, but since this list is plenty of very knowledgeable colleagues, I'm tempted to ask... I need to cool several resistive loads, in the order of 5kW, and I plan to use a cold plate and a liquid-to-liquid heat exchanger like the Lytron LCS-20, but this unit is quite big, and an overkill (it has 20kW capability). If someone could suggest me a smaller liquid-to-liquid heat exchanger, and preferably a rack mount unit (and share any experience), it would be most welcome. Since this has not too much to do with time and frequency, please answer off list. Thank you very much! Best regards, Javier __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Tom Harris celephi...@gmail.com ___ 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] WOT: Identify this movie
Sounds like the OP's story was from Harry Harrison's nightmarish novel of overpopulation Make Room, Make Room!. Incidentally I do not know the Lovecraft story mentioned below, do you have a title? A circular rotating prison sounds like a nightmare from the 20th century's other great fantasist Borges, who also wrote stories where time was twisted and stopped, to remain true to the list :) On 25 September 2012 18:14, d.sei...@comcast.net wrote: It sounds familiar, but I can't put a finger on it. For some reason, it reminds me of the Lovecraft story about the circular prison complex that the prisoners had to rotate one cell at a time via a big rope once a day. .. -Dave - Original Message - From: Bill Hawkins b...@iaxs.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Monday, September 24, 2012 11:05:13 PM Subject: [time-nuts] WOT: Identify this movie It's a dark and quiet night, and list traffic is way down, so please forgive me for this way off topic request. I'm writing a book about automation and have a chapter on the future thereof. I have a dim memory of a TV show or movie in black and white that has the teeming billions of earth living in high-rise buildings, each in a self- contained room. Occasionally, they work by pedaling a machine that generates electricity for the tower. Their leader exorts them to work harder through a wall-sized TV set. Does anybody recognize that scenario? At least one writer has suggested welfare dormitories for the 50% of workers made redundant by automation around 2050. Would like to get it into the book if I had a reference. Note the use of a time in the future to stay near topic. 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. ___ 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. -- Tom Harris celephi...@gmail.com ___ 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] GPSDO control loops and correcting quantization error
Second the comments on implementing a 16 bit DAC. You need separate analogue/digital grounds, superb voltage references, and lots of attempts to get a good design that actually uses the L.S. bit (rather than losing it in the noise). What you can do is use a second DAC to offset the 16 bit DAC. The offset DAC need only be 8 bit, as long as it is stable. I used this to autozero the output of a photomultiplier amplifier, and I needed about 20 bits to get the correct resolution. However, it can be tricky to adjust the offset DAC without jumps in the output. Incidentally superb experimental design, circuit boards taped to an odd piece of cardboard, with jumpers leads to tie everything together :). I use a dab of hot melt glue to do similar, and it can be used to secure wiring as well. On 15 September 2012 07:01, Don Latham d...@montana.com wrote: Michael: Actually implementing a 16 bit DAC to its 1-bit minimum resolution will be headache enough. You will gain a real education in good grounding practice, shielding, power supply stability and noise, and other Murphy intrusion. A 32 bit DAC IMHO, is impossible, and that's the name of that tune. Don Chris Albertson On Fri, Sep 14, 2012 at 11:21 AM, Michael Tharp g...@partiallystapled.com wrote: Finally, do people think a 16 bit DAC is adequate or should I consider building a 32-bit one? I looked at a few designs when putting this together but decided to keep it simple until things were up and running. Having a 32-bit DAC would give you enough range so that you could drop in any OCXO you might have. But if you can have trimmer resisters to selected for your specif OCXO then 16-bits should be enough. If it were me, I'd want the DAC steps to be smaller than what the phase detector can measure. Said another way a 32-bit DAC might eliminate the need for scale and offset trimmer resistors. Chris Albertson Redondo Beach, California ___ 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. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. De Erroribus Medicorum, R. Bacon, 13th century. If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com ___ 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. -- Tom Harris celephi...@gmail.com ___ 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] DCF77 Generation
Thanks for this, the idea of using a serial port to generate the DCF77 data in WWVB3.C is most ingenious. We may actually have to do this as the braindead modem that were were using for initial development has a timing resolution of 18.461ms, so impossible to do times that are multiples of 100ms :) Oh well, if engineering was easy, everyone would do it. On 8 September 2012 00:24, Tom Van Baak t...@leapsecond.com wrote: See wwvb1.c wwvb2.c wwvb3.c under my www.leapsecond.com/tools/ directory. There's some DCF77 support as I recall. Contact me offline if you have questions. /tvb - Original Message - From: Tom Harris celephi...@gmail.com To: time-nuts@febo.com Sent: Friday, September 07, 2012 5:53 AM Subject: [time-nuts] DCF77 Generation Greetings, I have just written some code for generating DCF77 pulses given a 100ms clock interrupt and an accurate timestamp from a RTC, for a mate who has to get some imported clock movements synced up (we are in Australia which has no radio time service). I did a quick search and found very little out there from people generating their own DCF77 data, so I thought I'd ask if anyone else has ever done anything similar (and why as well). We are not transmitting, only faking the output from a DCF77 receiver. -- Dr. Celephicus ___ 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. -- Tom Harris celephi...@gmail.com ___ 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] DCF77 Generation
Greetings, I have just written some code for generating DCF77 pulses given a 100ms clock interrupt and an accurate timestamp from a RTC, for a mate who has to get some imported clock movements synced up (we are in Australia which has no radio time service). I did a quick search and found very little out there from people generating their own DCF77 data, so I thought I'd ask if anyone else has ever done anything similar (and why as well). We are not transmitting, only faking the output from a DCF77 receiver. -- Dr. Celephicus ___ 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] Anyone got a reference for perpetual motion advert in New Scientist?
I've always found New Scientist very helpful, why not contact them directly? Mind you, they did publish Rupert Sheldrake's Formative Causation paper, and presumably not for payment... On 30 June 2012 07:03, David Kirkby david.kir...@onetel.net wrote: About 20-25 years ago someone took out an advert around 7 pages long in New Scientist. In this advert, he published a scientific paper, since no mainstream journal would publish his paper. I -- Tom Harris celephi...@gmail.com ___ 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] In the atomclock repairshop...
The portrait of your good self on page 4 A night seance in rubidium lamp light is superb, I would guess that this is inspired by a LP sleeve. It looks like it was painted by Joseph Wright of Derby, who lived about 250 years ago and who was the first painter to paint scientific subjects, and who was the master of lighting his subjects with a single candle. On 26 April 2012 05:06, Magnus Danielson mag...@rubidium.dyndns.org wrote: Fellow time-nuts, Oh, ok. So now it is public, so I better tell you about it... Jörgen Städje is a tech-writer which enjoys writing articles where he dips into some system and writes about it. Trying to teach things. Demystify things. So, when you read it, please recall that the audience is not very into the subject. It's in Swedish, but since you all know it by heart (or maybe using Babelfish) I think you surely enjoy it... http://www.idg.se/2.1085/1.**443818/i-atomurmakarens-**verkstadhttp://www.idg.se/2.1085/1.443818/i-atomurmakarens-verkstad The photo-session was not all that well-planned, but enjoy the more intimate photos of among others my Russian CH1-78 / HG414A. Various splashes of instruments. One of the photos has direct inspiration from an LP. Extra points from identifying which album. :) Oh well. Hope you enjoy it for what it is. Hope you can handle the chock of seeing photos of me. Cheers, Magnus - another time-nut outed by a journalist __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Tom Harris celephi...@gmail.com ___ 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] New unit of time measurement
Actually a friend who lived in Rome proposed a new European definition of the nanosecond as the time between the lights going green and the sound of the horn of the car behind you. I still remember driving in the rushhour in Rome, now _that_ was scary. On 15 January 2012 14:40, Skip Withrow skip.with...@gmail.com wrote: Dear nuts, I would like to propose a new unit of time, the 'textsecond'. This is the interval of time from the time the signal light turns green to when the driver behind the idiot texting driver honks their horn. Still collecting data on its exact length, but seeing a lot more examples lately. I'm sure there is probably a much more clever name (and there are a lot of clever time-nuts out there). However, I don't want this comment on social behaviour to blossom into a lengthy OT thread. Regards, Skip Withrow ___ 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. -- Tom Harris celephi...@gmail.com ___ 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] Thunderbolt? (re simple gpsdo.)
I too have been mulling over a minimal GPSDO. Has anyone mentioned a PWM DAC? Even a toy microcontroller like the Atmel AVRs can generate 16 bit resolution PWM, which sounds like it would be heaps. As long as the voltage reference is low noise, it does not matter if it drifts slowly, since the control loop adjusting the OCXO frequency will adjust it. Of course you will need a long time constant filter to smooth the PWM, but a 2 pole filter constructed from an opamp will do the job. The micro can also capture the 1PPS from the GPS if it is clocked by the OCXO, and use the value to close the control loop. So a minimal GPSDO looks like a simple microcontroller (I would use Arduino since we use these at work whenever we need to build something in an afternoon) with a filter for a PWM DAC, so one opamp and a few discretes. Of course as I write software for such beasts as a trade I am giving the software a zero cost. On 31 December 2011 06:46, Stanley timen...@n4iqt.com wrote: What is the simplest design for a GPSDO that uses only the PPS signal from a modern GPS? Some sort of oscillator with a voltage control. CPU with a timer/counter that can capture the PPS. DAC. Software. How about MSC1200 : http://www.ti.com/lit/ds/symlink/msc1200y3.pdf Stanley ___ 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. -- Tom Harris celephi...@gmail.com ___ 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] Thunderbolt? (re simple gpsdo.)
Kasper, I like your style! Small ROM = no inessential features! I shall be studying this code, getting capture working with no capture hardware is a real pain. On 2 January 2012 00:53, Kasper Pedersen time-n...@kasperkp.dk wrote: On 01/01/2012 12:23 PM, Tom Harris wrote: I too have been mulling over a minimal GPSDO. Has anyone mentioned a PWM DAC? Even a toy microcontroller like the Atmel AVRs can generate 16 bit resolution PWM, which sounds like it .. So a minimal GPSDO looks like a simple microcontroller (I would use Arduino since we use these at work whenever we need to build something in an afternoon) with a filter for a PWM DAC, so one opamp and a few discretes. Of course as I write software for such beasts as a trade I am giving the software a zero cost. A 'bike light' sized microcontroller can do the job. Today I would have used something larger, and saved development time. On the other hand, having only room for 512 instructions prevented spending time on non-essential features. http://n1.taur.dk/simplexdo/ I used 8 bit PWM into a two-stage RC filter, making it easier to filter. To get 16 bit resolution I added delta-sigma modulation on top of the PWM. The ATTiny13 is not the right part for the job; It has no input capture. So space- and time consuming tricks are necessary to get cycle-accurate capture. Recently I discovered that some of the microcontrollers in the drawer would do nanosecond capture all on their own, but with a working tbolt, need has been lacking. /Kasper Pedersen ___ 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. -- Tom Harris celephi...@gmail.com ___ 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] Using GPS 1PPS for accurate period measurement
I finally have a need to ask a question about time measurement! I want to measure the accuracy of a 1Hz signal from a real time clock (RTC) chip with an integrated TXCO allegedly good for +/- 2ppm accuracy. My employer is too tight to buy a good frequency counter, but I do have a GPS module outputting 1PPS. If I use a little micro running at 16MHz from a jellybean crystal to measure the period of the 1PPS signal from the GPS concurrently with measuring the period of my test signal, will I be able to get accuracy of sub ppm? My resolution for a single period is 62.5 ppb, but this is a lot different to accuracy. I could easily count multiple periods, as I do not need fast results. My thought is that the 16MHz will have jitter and a pronounced drift, but that as the measurements of my reference and signal are done nearly concurrently, the errors will be very small. The need for this is that the RTC chip for a product has the engaging property of shifting it's frequency by several ppm after being soldered to the board, and I need to characterise this to get accurate timing for the product. -- Tom Harris celephi...@gmail.com ___ 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.
