[time-nuts] Looking for the hp Standard
Some of you know that I'm a pack-rat for vintage instruments, books, documentation, and publications about atomic clocks. Especially anything by Hewlett-Packard. I've enjoyed all the time-nuts posting by Rick Karlquist and Hugh Rice, et al. The usual online hp sources [1] host the massive annual hp catalogs, monthly issues of the hp Journal, hp Measure magazine, hp Application Notes, hp Operation & Service manuals, hp Bench Briefs magazine, etc. But they miss one publication called "the hp Standard". I have a pile of them but I know it's not complete. My question today is -- do any of you have old issues of the publication called "the hp standard"? The issues I have are shown here: http://leapsecond.com/history/the-hp-standard.htm I'm trying to fill in the missing issues. I'm still unloading shelves and unpacked boxes but if you have old xerox copies or original hardcopy of hp STANDARD please let me know. I'll post the PDF's to time-nuts when I have a complete collection. I'm almost there... Thanks, /tvb [1] Worth a weekend of cesium reading... www.hpmemoryproject.org www.hparchive.com/ www.hparchive.com/hp_journals www.hparchive.com/measure www.hparchive.com/bench_briefs www.hpmuseum.net/ www.hpl.hp.com/hpjournal/journal.html www.hp.com/hpinfo/abouthp/histnfacts/publications/measure/ www.ko4bb.com/manuals.html www.leapsecond.com/hpclocks/ ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Looking for the hp Standard
n Mon, 25 Mar 2019 at 10:03, Tom Van Baak wrote: > Some of you know that I'm a pack-rat for vintage instruments, books, > documentation, and publications about atomic clocks. Especially anything by > Hewlett-Packard. I've enjoyed all the time-nuts posting by Rick Karlquist > and Hugh Rice, et al. > /tvb > I generally find the old documents / manuals much more informative than the modern ones. To take just one example, I have an HP 16453A fixture that measured permittivity of dielectrics. https://www.keysight.com/en/pd-100508%3Aepsg%3Apro-pn-16453A/dielectric-material-test-fixture?cc=US&lc=eng I wanted to use it on an LCR meter, but its not so easy as the the plates are small, so finging capacitance can't be ignored. It is designed to work with instrument that have the firmware to handle it. There are no equations in the manual, nor any of the modern instruments designed for use with this. But if you look back at much older manuals, all the equations are there, which take into account the fringing field. For the last couple of decades at least, everything is considered interlectual property (IP) and is closely guarded by Keysight. But a search of older manuals, for equipment one does not own, often bears useful results. -- Dr David Kirkby Ph.D C.Eng MIET Kirkby Microwave Ltd Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD, Essex, CM3 6DT, United Kingdom. Registered in England and Wales as company number 08914892 https://www.kirkbymicrowave.co.uk/ Tel 01621-680100 / +44 1621-680100 ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Looking for the hp Standard
Very nice! I look forward to reading all of those. I hadn't known of that publication. Bob On Monday, March 25, 2019, 3:03:12 AM PDT, Tom Van Baak wrote: Some of you know that I'm a pack-rat for vintage instruments, books, documentation, and publications about atomic clocks. Especially anything by Hewlett-Packard. I've enjoyed all the time-nuts posting by Rick Karlquist and Hugh Rice, et al. The usual online hp sources [1] host the massive annual hp catalogs, monthly issues of the hp Journal, hp Measure magazine, hp Application Notes, hp Operation & Service manuals, hp Bench Briefs magazine, etc. But they miss one publication called "the hp Standard". I have a pile of them but I know it's not complete. My question today is -- do any of you have old issues of the publication called "the hp standard"? The issues I have are shown here: http://leapsecond.com/history/the-hp-standard.htm I'm trying to fill in the missing issues. I'm still unloading shelves and unpacked boxes but if you have old xerox copies or original hardcopy of hp STANDARD please let me know. I'll post the PDF's to time-nuts when I have a complete collection. I'm almost there... Thanks, /tvb [1] Worth a weekend of cesium reading... www.hpmemoryproject.org www.hparchive.com/ www.hparchive.com/hp_journals www.hparchive.com/measure www.hparchive.com/bench_briefs www.hpmuseum.net/ www.hpl.hp.com/hpjournal/journal.html www.hp.com/hpinfo/abouthp/histnfacts/publications/measure/ www.ko4bb.com/manuals.html www.leapsecond.com/hpclocks/ ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] multimeter
The 87 is a good general purpose meter. My preference has been the now obsolete Fluke 189. It was replaced with the 289, which is just horrible. It eats batteries, is huge, takes forever to 'boot'. No one in the ship grabs that one unless it's the last one on the shelf. We've gone to orange meters now that we can't get more 189's. The Keysignt U1272A has been a good replacement in our shop for the 189. I also have a U1241B, and am quite happy with it. I find myself reaching for the U1241B more often than the Fluke 189 as of late. It's smaller... All that said, I'm certain you'll be happy 87 for what you plan on doing with it. Dan On 3/24/2019 12:00 PM, time-nuts-requ...@lists.febo.com wrote: Message: 8 Date: Sun, 24 Mar 2019 18:00:12 +1100 From: Jim Palfreyman To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] multimeter Message-ID: Content-Type: text/plain; charset="UTF-8" Hi All, Thanks so much everyone for your comments. I especially liked "get the orange one". Because that's what I did get (I think it's orange - could be yellow). I was deliberately vague (apologies) but I just wanted a broad response. Which I got. I've settled on the Fluke 87V. It's on it's way. Jim ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] multimeter
I have both the 87 and the 189 (I agree re: the 289 - not to mention the expense...). The 189 stays in the shop, with rare exceptions. The 87, built like a tank, goes on the road in a padded case. Get an 87 and a set of very skinny, pointed probes for those tight places. You will be very happy. Ken WA2LBI On Mon, Mar 25, 2019 at 3:00 PM Dan Kemppainen wrote: > The 87 is a good general purpose meter. My preference has been the now > obsolete Fluke 189. It was replaced with the 289, which is just > horrible. It eats batteries, is huge, takes forever to 'boot'. No one in > the ship grabs that one unless it's the last one on the shelf. > > We've gone to orange meters now that we can't get more 189's. The > Keysignt U1272A has been a good replacement in our shop for the 189. > > I also have a U1241B, and am quite happy with it. I find myself reaching > for the U1241B more often than the Fluke 189 as of late. It's smaller... > > All that said, I'm certain you'll be happy 87 for what you plan on doing > with it. > > Dan > > > > > On 3/24/2019 12:00 PM, time-nuts-requ...@lists.febo.com wrote: > > Message: 8 > > Date: Sun, 24 Mar 2019 18:00:12 +1100 > > From: Jim Palfreyman > > To: Discussion of precise time and frequency measurement > > > > Subject: Re: [time-nuts] multimeter > > Message-ID: > >nivi8vitrhha74k...@mail.gmail.com> > > Content-Type: text/plain; charset="UTF-8" > > > > Hi All, > > > > Thanks so much everyone for your comments. I especially liked "get the > > orange one". Because that's what I did get (I think it's orange - could > be > > yellow). > > > > I was deliberately vague (apologies) but I just wanted a broad response. > > Which I got. > > > > I've settled on the Fluke 87V. It's on it's way. > > > > Jim > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Oscillator Aging Trends
Hi Very nice plots and some useful information. At some point the question becomes what the 8607 is doing. Both are seeing changes in temperature (and pressure). Eventually that will get into the picture. From the plots so far …. not so much yet. Will we be getting weekly updates for the next couple years? :) Bob > On Mar 25, 2019, at 2:32 PM, John Ackermann N8UR wrote: > > Here are two more of those neat images-worth-a-thousand-words that sometimes > show up. > > I've been testing an Oscilloquartz 8600B BVA and did a series of 24 hour > measurements over about a week, starting a day after powering it up. When you > put all the ADEV plots on a single chart, you can see how the performance > improves day over day. If you put the frequency plots on one graph with > "start at zero" selected, the sequential improvement is really dramatic. > > John > > (Notes: 1. The reference was an 8607 BVA that's been running continuously > for several years. 2. There are a few hours of dead time between the end of > most runs and the beginning of the next. There's about three days of dead > time before the final run because I was out of town.) > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Oscillator Aging Trends
On 3/25/19 3:08 PM, Bob kb8tq wrote: Hi Very nice plots and some useful information. At some point the question becomes what the 8607 is doing. Both are seeing changes in temperature (and pressure). Eventually that will get into the picture. From the plots so far …. not so much yet. The 8607 is believed to be an order of magnitude or so better at this point, but I'm doing a measurement of the 8600 vs. 5065A to make sure. Since I'm looking at relative drift here, as long as the 8607 aging rate is stable, it shouldn't interfere with the take-away. Will we be getting weekly updates for the next couple years? :) Nope, the 8600 is just a temporary guest. :-( John ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] multimeter
You're so right about the 289. It costs too much, sucks the life out of batteries and is way too big. I have about a dozen handheld MMs, from a piece of Harbor Freight trash to a Gossen Metrahit M248A (believe it or not, a gift from a widow, off her late husband's bench. NIB). My 87 is the one I use the most. You know what I use my 289 for? Tracking internal temp on the Christmas turkey and the occasional hunk of roast beef. It may not be the most desirable multimeter but it's one hell of a meat thermometer! On Monday, March 25, 2019, Dan Kemppainen wrote: > The 87 is a good general purpose meter. My preference has been the now > obsolete Fluke 189. It was replaced with the 289, which is just horrible. > It eats batteries, is huge, takes forever to 'boot'. No one in the ship > grabs that one unless it's the last one on the shelf. > > We've gone to orange meters now that we can't get more 189's. The Keysignt > U1272A has been a good replacement in our shop for the 189. > > I also have a U1241B, and am quite happy with it. I find myself reaching > for the U1241B more often than the Fluke 189 as of late. It's smaller... > > All that said, I'm certain you'll be happy 87 for what you plan on doing > with it. > > Dan > > > > > On 3/24/2019 12:00 PM, time-nuts-requ...@lists.febo.com wrote: > >> Message: 8 >> Date: Sun, 24 Mar 2019 18:00:12 +1100 >> From: Jim Palfreyman >> To: Discussion of precise time and frequency measurement >> >> Subject: Re: [time-nuts] multimeter >> Message-ID: >> > gmail.com> >> Content-Type: text/plain; charset="UTF-8" >> >> Hi All, >> >> Thanks so much everyone for your comments. I especially liked "get the >> orange one". Because that's what I did get (I think it's orange - could be >> yellow). >> >> I was deliberately vague (apologies) but I just wanted a broad response. >> Which I got. >> >> I've settled on the Fluke 87V. It's on it's way. >> >> Jim >> > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/ > listinfo/time-nuts_lists.febo.com > and follow the instructions there. > -- ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[time-nuts] Absolute time accuracy pre-Cesium?
Does anyone have a pointer to information about the absolute time accuracy (not stability) that was available via PZT or other techniques prior to the Cesium definition? I'm doing a presentation and want to show the evolution of accuracy. My Google-fu has failed me in finding anything pre-Atomic. Thanks! John ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Absolute time accuracy pre-Cesium?
John http://adsabs.harvard.edu/full/1968JRASC..62..205T indicates a timing accuracy of a few milliseconds was typical for the Calgary PZT. Bruce > On 26 March 2019 at 11:44 John Ackermann N8UR wrote: > > > Does anyone have a pointer to information about the absolute time > accuracy (not stability) that was available via PZT or other techniques > prior to the Cesium definition? I'm doing a presentation and want to > show the evolution of accuracy. My Google-fu has failed me in finding > anything pre-Atomic. > > Thanks! > John > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Absolute time accuracy pre-Cesium?
https://www.cambridge.org/core/services/aop-cambridge-core/content/view/FFA10ED6A784AA1E39637CC0CA93B750/S0074180900036007a.pdf/div-class-title-some-advantages-and-disadvantages-of-a-photographic-zenith-tube-div.pdf indicates a timing error of around 6 millisec Bruce > On 26 March 2019 at 12:15 Bruce Griffiths wrote: > > > John > http://adsabs.harvard.edu/full/1968JRASC..62..205T > indicates a timing accuracy of a few milliseconds was typical for the Calgary > PZT. > > Bruce > > On 26 March 2019 at 11:44 John Ackermann N8UR wrote: > > > > > > Does anyone have a pointer to information about the absolute time > > accuracy (not stability) that was available via PZT or other techniques > > prior to the Cesium definition? I'm doing a presentation and want to > > show the evolution of accuracy. My Google-fu has failed me in finding > > anything pre-Atomic. > > > > Thanks! > > John > > > > > > ___ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe, go to > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Absolute time accuracy pre-Cesium?
On Mon 2019-03-25T18:44:05-0400 John Ackermann N8UR hath writ: > Does anyone have a pointer to information about the absolute time accuracy > (not stability) that was available via PZT or other techniques prior to the > Cesium definition? I'm doing a presentation and want to show the evolution > of accuracy. My Google-fu has failed me in finding anything pre-Atomic. https://www.ucolick.org/~sla/leapsecs/annastoyko.html -- Steve Allen WGS-84 (GPS) UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 https://www.ucolick.org/~sla/ Hgt +250 m ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Absolute time accuracy pre-Cesium?
> Does anyone have a pointer to information about the absolute time > accuracy (not stability) that was available via PZT or other techniques > prior to the Cesium definition? I'm doing a presentation and want to > show the evolution of accuracy. My Google-fu has failed me in finding > anything pre-Atomic. > > Thanks! > John A nice example of how good astronomical timing was is how they calibrated cesium atomic time against astronomical time. The original 1958 paper is here: http://leapsecond.com/history/1958-PhysRev-v1-n3-Markowitz-Hall-Essen-Parry.pdf What you see there is that they spent 4(!) years and took 4(!) data points to precisely compare the best astronomical clock with the first cesium clock. It appears they got millisecond accuracy in their timings. Compared against the existing astronomical clock standard, the four measurements of cesium frequency were: 9 192 631 761 9 192 631 767 9 192 631 772 9 192 631 780 Do the math: the mean is 9 192 631 770 +/- 8 Hz. That, literally, is where the magic 9192.631770 MHz cesium number and definition of the SI second comes from. That suggests the precision was 8 Hz / 9192631770 Hz, which is 8.7e-10, the equivalent of 75 us/day, or 2 ms/month, or 27 ms/year. As a practical matter a more accurate value of 9192631770 would have been useless because the earth is less stable than 8e-10 anyway. Here, for example, is how different UTC and UT1 would be depending on how the cesium SI second had been defined: http://www.leapsecond.com/pages/ut/cs9192-ut1-ani.gif http://www.leapsecond.com/pages/ut/ In retrospect we would have had fewer leap seconds if they had chosen 9192631950 Hz instead of 9192631770 Hz. But at the time it wasn't a choice; it was just a measurement. /tvb ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] multimeter
I have long felt that the 289 is a classic example of design by committee. It has every possible feature that no one wants or needs and a price that represents that, but not the features people actually care about in a meter (fast turn on, rugged, light weight, reliable, long battery life.) Matthew Sent from Matthew D'Asaro's iPhone > On Mar 25, 2019, at 1:31 PM, William H. Fite wrote: > > You're so right about the 289. It costs too much, sucks the life out of > batteries and is way too big. > > I have about a dozen handheld MMs, from a piece of Harbor Freight trash to > a Gossen Metrahit M248A (believe it or not, a gift from a widow, off her > late husband's bench. NIB). My 87 is the one I use the most. You know what > I use my 289 for? Tracking internal temp on the Christmas turkey and the > occasional hunk of roast beef. > > It may not be the most desirable multimeter but it's one hell of a meat > thermometer! > > > >> On Monday, March 25, 2019, Dan Kemppainen wrote: >> >> The 87 is a good general purpose meter. My preference has been the now >> obsolete Fluke 189. It was replaced with the 289, which is just horrible. >> It eats batteries, is huge, takes forever to 'boot'. No one in the ship >> grabs that one unless it's the last one on the shelf. >> >> We've gone to orange meters now that we can't get more 189's. The Keysignt >> U1272A has been a good replacement in our shop for the 189. >> >> I also have a U1241B, and am quite happy with it. I find myself reaching >> for the U1241B more often than the Fluke 189 as of late. It's smaller... >> >> All that said, I'm certain you'll be happy 87 for what you plan on doing >> with it. >> >> Dan >> >> >> >> >>> On 3/24/2019 12:00 PM, time-nuts-requ...@lists.febo.com wrote: >>> >>> Message: 8 >>> Date: Sun, 24 Mar 2019 18:00:12 +1100 >>> From: Jim Palfreyman >>> To: Discussion of precise time and frequency measurement >>> >>> Subject: Re: [time-nuts] multimeter >>> Message-ID: >>>>> gmail.com> >>> Content-Type: text/plain; charset="UTF-8" >>> >>> Hi All, >>> >>> Thanks so much everyone for your comments. I especially liked "get the >>> orange one". Because that's what I did get (I think it's orange - could be >>> yellow). >>> >>> I was deliberately vague (apologies) but I just wanted a broad response. >>> Which I got. >>> >>> I've settled on the Fluke 87V. It's on it's way. >>> >>> Jim >> >> ___ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to http://lists.febo.com/mailman/ >> listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > > -- > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Absolute time accuracy pre-Cesium?
On Mon 2019-03-25T16:54:28-0700 Tom Van Baak hath writ: > In retrospect we would have had fewer leap seconds if they had > chosen 9192631950 Hz instead of 9192631770 Hz. But at the time it > wasn't a choice; it was just a measurement. And it was a measurement which was performed during an interval when everyone was surprised by the data they were seeing. Around the beginning of 1957 the rotation of the earth's crust shifted suddenly as seen in the USNO plot of UT2 at the bottom of https://www.ucolick.org/~sla/leapsecs/amsci.html At the time that the paper giving 9192631770 was published nobody was sure whether this was an actual change in the earth or some failure to understand cesium frequency standards. It was a few years before it had become clear that earth rotation has a power spectrum of random fluctuations. Over time the BIH had the opportunity to watch cesium vs. Ephemeris Time for more years than the original papers. In 1964 Anna Stoyko found a value of the cesium frequency 9192631799 Hz w.r.t. Ephemeris Time (Bulletin Horaire ser 6 no 7 p 186). -- Steve Allen WGS-84 (GPS) UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 https://www.ucolick.org/~sla/ Hgt +250 m ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Absolute time accuracy pre-Cesium?
For independent standards (not quite what you asked) I recall from "The Science of Clocks and Watches" (a book with much technical info if you're interested in these mechanical devices) that the most accurate mechanical/pendulum clock was the Shortt Clock that used a pendulum in a vacuum chamber for its standard. Mechanical clocks were replaced by more stable electronic quartz crystal oscillators, and then finally by atomic clocks. Perhaps closer to your question: I recall in my readings about clockmaker John Harrison (likely either in "The Quest for Longitude" or Dava Sobel's "Longitude") that he would look from the edge of his window at a particular star each night and note (while counting the ticks he heard from his clock) the exact moment it would disappear behind a nearby chimney, and knowing the Earth's rotation takes four minutes and some (I forget) seconds off from a day, he used this to calibrate and test the precision and accuracy of his long clocks. It was suggested he could get within less than second with this method. This was around age 21, so the year would be about 1714. Looking online for PZT (photographic zenith tube), I didn't find much about it, but it was surely first made a couple centuries after this. The Sobel book (all about how Harrison won the Longitude prize) is more a popular book and less technical, but "Quest" has many mostly-technical articles, mostly about Harrison, as well as beautiful photos of his clocks. One or two of the articles is by the man who made (or made the parts for it, the story is complicated) the one-second-in-100-days "Clock B" pendulum clock, built from Harrison's writings and claims of just that accuracy in the book he wrote shortly before his death. On Mon, Mar 25, 2019 at 7:00 PM John Ackermann N8UR wrote: > > Does anyone have a pointer to information about the absolute time > accuracy (not stability) that was available via PZT or other techniques > prior to the Cesium definition? I'm doing a presentation and want to > show the evolution of accuracy. My Google-fu has failed me in finding > anything pre-Atomic. > > Thanks! > John > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Absolute time accuracy pre-Cesium?
If I am reading the paper correctly they used the moon as the reference. I would have thought it was the sun. But the moon gives a very clean edge definition. And now I know how the 770 came about. One more bit in the knowledge bunker. Thanks Paul WB8TSL On Mon, Mar 25, 2019 at 8:03 PM Tom Van Baak wrote: > > Does anyone have a pointer to information about the absolute time > > accuracy (not stability) that was available via PZT or other techniques > > prior to the Cesium definition? I'm doing a presentation and want to > > show the evolution of accuracy. My Google-fu has failed me in finding > > anything pre-Atomic. > > > > Thanks! > > John > > A nice example of how good astronomical timing was is how they calibrated > cesium atomic time against astronomical time. The original 1958 paper is > here: > > > http://leapsecond.com/history/1958-PhysRev-v1-n3-Markowitz-Hall-Essen-Parry.pdf > > What you see there is that they spent 4(!) years and took 4(!) data points > to precisely compare the best astronomical clock with the first cesium > clock. It appears they got millisecond accuracy in their timings. Compared > against the existing astronomical clock standard, the four measurements of > cesium frequency were: > > 9 192 631 761 > 9 192 631 767 > 9 192 631 772 > 9 192 631 780 > > Do the math: the mean is 9 192 631 770 +/- 8 Hz. That, literally, is where > the magic 9192.631770 MHz cesium number and definition of the SI second > comes from. That suggests the precision was 8 Hz / 9192631770 Hz, which is > 8.7e-10, the equivalent of 75 us/day, or 2 ms/month, or 27 ms/year. > > As a practical matter a more accurate value of 9192631770 would have been > useless because the earth is less stable than 8e-10 anyway. Here, for > example, is how different UTC and UT1 would be depending on how the cesium > SI second had been defined: > > http://www.leapsecond.com/pages/ut/cs9192-ut1-ani.gif > http://www.leapsecond.com/pages/ut/ > > In retrospect we would have had fewer leap seconds if they had chosen > 9192631950 Hz instead of 9192631770 Hz. But at the time it wasn't a choice; > it was just a measurement. > > /tvb > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[time-nuts] F9T Info
Hi Looks like uBlox has released the basic info on the protocols and interfacing of the F9T. https://www.u-blox.com/en/product/zed-f9t-module#tab-documentation-resources There are still a few documents referenced in what they did release that have not yet popped up on the web site. Still looking for something past FW 2.00 ….. Bob ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
