[time-nuts] FOSDEM 2015 has a time-track
FOSDEM is an Open-Source gathering once a year in Bruxelles, and this year there is a track dedicated to time: https://fosdem.org/2015/schedule/track/time/ Those of you of an european persuassion may find it relevant... -- 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.
Re: [time-nuts] VC-OCXO EFC stability.
In that case, it all depends on what you're trying to accomplish. If you're using WWV or something like that to set the frequency, then the 78L05 should be fine. Bob From: ct1dmk ct1...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tuesday, January 6, 2015 7:35 PM Subject: Re: [time-nuts] VC-OCXO EFC stability. Hi Bob, That is the issue, it doesn't. (the 2,3 different types I would like to use none of them have it, so I will be making a small pcb with the trimpot and the regulator and some capacitors etc). Luis Cupido. ct1dmk On 1/7/2015 1:09 AM, Bob Stewart wrote: Does your oscillator have a VRef output? If so, use that instead of a regulator. It's cleaner and usually temperature compensated. Bob From: ct1dmkct1...@gmail.com To: Discussion of precise time and frequency measurementtime-nuts@febo.com Sent: Tuesday, January 6, 2015 6:40 PM Subject: [time-nuts] VC-OCXO EFC stability. Hi, With a multiturn pot and a 78L05 I can get a 0 to 5V EFC to tune an OCXO on desired freq. But... maybe other voltage regulators or other scheme have better temp stability than the old 78L05. Before I crawl lost in new'ish fancy regulator land does anybody know the killer solution/IC for this job ? Luis Cupido ct1dmk. ___ 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.
Re: [time-nuts] VC-OCXO EFC stability.
I tried something like that once just to discover that the OCXO VFC port had low impedance, so my voltage divider didn´t behave very well. So i put an amp op in unitary gain configuration between the two and things improved a lot. Then I changed the amp op for a DP precision part and things improved again. Then I choose resistors/trim pot with low TCR for the voltage divider and things improved again. Then I made a good layout, termally coupling the resistors well, you see this has no end :) Daniel On 06/01/2015 22:40, ct1dmk wrote: Hi, With a multiturn pot and a 78L05 I can get a 0 to 5V EFC to tune an OCXO on desired freq. But... maybe other voltage regulators or other scheme have better temp stability than the old 78L05. Before I crawl lost in new'ish fancy regulator land does anybody know the killer solution/IC for this job ? Luis Cupido ct1dmk. ___ 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] VC-OCXO EFC stability.
Luis If you have sufficient headroom (input supply 7V or so) why not use a buried zener reference chip like an LT1027? These chips also have a noise reduction pin. Otherwise a lower dropout bandgap reference like an LT1019 or similar may be useful. Bruce On Wednesday, January 07, 2015 01:35:59 AM ct1dmk wrote: Hi Bob, That is the issue, it doesn't. (the 2,3 different types I would like to use none of them have it, so I will be making a small pcb with the trimpot and the regulator and some capacitors etc). Luis Cupido. ct1dmk On 1/7/2015 1:09 AM, Bob Stewart wrote: Does your oscillator have a VRef output? If so, use that instead of a regulator. It's cleaner and usually temperature compensated. Bob From: ct1dmkct1...@gmail.com To: Discussion of precise time and frequency measurementtime-nuts@febo.com Sent: Tuesday, January 6, 2015 6:40 PM Subject: [time-nuts] VC-OCXO EFC stability. Hi, With a multiturn pot and a 78L05 I can get a 0 to 5V EFC to tune an OCXO on desired freq. But... maybe other voltage regulators or other scheme have better temp stability than the old 78L05. Before I crawl lost in new'ish fancy regulator land does anybody know the killer solution/IC for this job ? Luis Cupido ct1dmk. ___ 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.
Re: [time-nuts] June 30 2015 leap second
The difference between GPS time and UTC (due to leap seconds) is broadcast in the GPS navigation message[1] so all but the most poorly designed GPS modules should take care of it and output the correct UTC time. Henry, This is not quite true. First, page 18 of subframe 4 is only broadcast every 12.5 minutes so on a cold start worst case you wait up to 12.5 minutes before the receiver can *reliably* switch from GPS time to UTC time. This would not likely be an issue for the OP since his clock would keep the GPS receiver powered-on. Second, the OP is building a clock. A precise clock needs a 1PPS and it needs to know what date-time that 1PPS *will* be. The NMEA sentences only tell you what date-time the 1PPS *was*. This is the crux of the problem. Two solutions: 1) relax the requirements of the clock and allow it to display NMEA time, which will be late by tens to hundreds of ms. This also assumes the NMEA implementation of the receiver outputs hh:59:60 (many don't). Or 2), use proprietary binary messages from the receiver to get advanced warning of a pending leap second event and then role your own leap second special case code. The latter solution has a rare timing window if you turn on the clock too close to the leap second itself. /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.
Re: [time-nuts] VC-OCXO EFC stability.
Hi If you find that your EFC port is low impedance - check it for a bias voltage. It may well have a pull up resistor to an internal Vref. The intent is that you simply tune it with a resistance to ground. Bob On Jan 6, 2015, at 8:49 PM, Daniel Mendes dmend...@gmail.com wrote: I tried something like that once just to discover that the OCXO VFC port had low impedance, so my voltage divider didn´t behave very well. So i put an amp op in unitary gain configuration between the two and things improved a lot. Then I changed the amp op for a DP precision part and things improved again. Then I choose resistors/trim pot with low TCR for the voltage divider and things improved again. Then I made a good layout, termally coupling the resistors well, you see this has no end :) Daniel On 06/01/2015 22:40, ct1dmk wrote: Hi, With a multiturn pot and a 78L05 I can get a 0 to 5V EFC to tune an OCXO on desired freq. But... maybe other voltage regulators or other scheme have better temp stability than the old 78L05. Before I crawl lost in new'ish fancy regulator land does anybody know the killer solution/IC for this job ? Luis Cupido ct1dmk. ___ 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] June 30 2015 leap second
The difference between GPS time and UTC (due to leap seconds) is
broadcast in the GPS navigation message[1] so all but the most poorly
designed GPS modules should take care of it and output the correct UTC
time.
I'm not going to get into the mess of unix epoch time. Basically,
it's not a continuous time scale. There is some information on the
wikipedia page[2], and plenty of discussion on various mailing lists
such as LEAPSECS.
Henry
[1] Specifically, page 18 of subframe 4 - see IS-GPS-200G page 112,
114 and 119-121.
[2] https://en.wikipedia.org/wiki/Unix_time#Leap_seconds
On Tue, Jan 6, 2015 at 1:01 PM, d0ct0r t...@patoka.org wrote:
Hello,
As I am in the process of creation of my own Nixie clocks. And it probably
good time frame to clarify one thing about leap seconds. In my project I am
using GPS module as an option to have current UTC time and also to have 1PPS
signal to do auto-adjustment for external RTC module. The question is how
usually GPS modules handle leap seconds ? Is it satelates who send UTC time
to GPS module or GPS module has firmware with leap second information
hard-coded ?
The same question is for UNIX epoch time. How computers knows if it is
necessary to add leap seconds ? Lets say I am using very simple script to
calculate UNIX time for specified date:
#!/usr/bin/perl
use Time::Local;
my ($d, $m, $y);
my $time;
@myYears = ('01/06/2000', '01/06/2015', '01/06/2038', '01/06/3000');
foreach (@myYears) {
($d, $m, $y) = split '/', $_;
$time = timelocal(0,0,0,$d,$m-1,$y);
printf %ld\n\r, $time;
}
==
It will produce the following output:
959832000
1433131200
2158977600
32516740800
I am not sure if its take leap second consideration. Most likely not. And
that means its only accurate for the present and pas time. Right ? For my
clock I already implement the function for the leap second and I am able to
add/remove number of seconds from the time I receiving from GPS or any other
source. But it will be more inetersting if clock could do it automagically
and shows me that famous 60 number without human interaction. Any advise
for this ? Thanks !
Regards,
V.P.
On , Tom Van Baak wrote:
Just announced: there will be a positive leap second at the end of
June 30 2015 UTC (that's Wednesday July 1st for most of the world).
As usual we time nuts will have a leap second party -- where we
capture and share the magic hh:59:60 display on as many different
clocks and instruments as possible.
/tvb
More info:
ftp://hpiers.obspm.fr/iers/bul/bulc/bulletinc.dat
http://hpiers.obspm.fr/eop-pc/
And for those of you who want to know how long each day really is:
ftp://hpiers.obspm.fr/iers/bul/bulb_new/bulletinb.dat
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--
WBW,
V.P.
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Re: [time-nuts] schematics of frequency counter
Charles Steinmetz csteinmetz@... writes: Actually, I dont want to ask my colledge for help. Everytime ,for each guy I ask for help, I need expain the entire system and principle of a frequency counter to him. They just keep asking questions instead of answering mine. In defense of the hardware guys, there are a lot of questions that NEED to be asked (and answered) before a design that fulfills your requirements can even be attempted. I don't mean to be unkind, but you skipped all of those questions, designed the software, and now you want someone to hand you a hardware design that solves the problems you are having. From what I can tell, you still don't even have a good concept of what the hardware needs to do, much less how to specify these needs as coherent project requirements -- and even less how to actually design the circuitry you need. Furthermore, when someone suggests something that might fix a glaring error in your design, you say you can't do that because (for example) PNP transistors are too expensive. Ask any competent engineering manager and you will learn that good analog design engineers are the rarest and hardest to find development team members, and that getting the hardware right is very often the hardest part of any design (note that I did not say, most time-consuming -- rather, hardest). So, now you need the analog hardware for your counter, and you have the mistaken impression that it shouldn't be any effort at all. Hopefully, you are now beginning to understand that at least as much good thinking needs to go into the hardware as into the software. And hopefully, you have reviewed the analog circuitry of some good commercial designs to see what sorts of things good analog designers have done in the past to solve the same problems you are facing. You said yourself that you don't really know anything about analog design, and your existing circuit and your comments here on the list show that to be an honest and true assessment. But you also have resisted advice you have gotten from experienced analog designers, and now you say you can't even be bothered to answer the questions of people who would try to help you! At this point, I'm afraid that whatever is posted on this thread isn't really going to help you improve on what you have -- it is just so much wasted internet bandwidth. You need to learn at least enough about analog design to ask and answer intelligent questions about your needs, and you need to be willing to consider the advice you receive, before any of this can help you. Best regards, Charles Hi Charles, I don't mean to offend hardware guys. I've got a lot of help from them. The questions I am talking are something like: my 2.4G counter costs only 10$, why do you want to build one? Why don't you multiply reference clock to 400M with your FPGA as reference? Why do you need so many digits? It's PLL age, who needs a frequency counter? ... On this list, a lot of experienced people like you have given me a lot of suggestions. If my words sound like resist advises I don't mean that. (I did say ADM7150 is too expensive and has different package that I can not use it now. However, I have done test of changing FPGA's current strength slew rate to see if the noise of TDC power supply matters.) Because some are easy to achieve on my current board, some need to modify the hardware. I choose the suggestions that can be done at the moment. Something like PNP transistor or low noise LDO need new board to verify. I have got some BFT92 and looking for pin-pin compatible low noise LDO to play with. Thanks Li Ang ___ 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] VC-OCXO EFC stability.
Luis wrote: With a multiturn pot and a 78L05 I can get a 0 to 5V EFC to tune an OCXO on desired freq. But... maybe other voltage regulators or other scheme have better temp stability than the old 78L05. Before I crawl lost in new'ish fancy regulator land does anybody know the killer solution/IC for this job ? First, think hard about whether you really want the full 0-5v EFC range. Even with a 25-turn pot, it can be difficult to adjust the frequency in very fine increments with the full EFC range across the pot, so it is often beneficial to restrict the range to get finer adjustment. Of course, the voltage that sets the oscillator exactly on frequency should be somewhere near the middle of the pot's adjustment range. (If you know which way the oscillator is drifting, you can leave more range in the direction that it will [most likely] need to be adjusted in the future, and less in the other direction.) One circuit that has very low noise, first-order temperature compensation, and gives a limited tuning range (for fine adjustment) is posted at ko4bb.com. Go to http://www.ko4bb.com/manuals/ and search for the file named: HP 10544 10811 EFC fine adjustment.pdf [searching for 10811 will find it] That circuit is designed to give a symmetrical EFC range of +/- 1.2v maximum, which can be reduced further by using fixed resistors at either end of the potentiometer. With slight modification, it could easily provide an EFC voltage from about 0.8v to about 3.2v, and by adding another LED and temperature-compensating diode the range could be increased to run from about 0.8v to about 4.4v. There are lots of other solutions, and I'm sure a number will be suggested. Do remember that most ultra-low noise voltage references are not really all that quiet (ultra is a relative term...), so be prepared to do some heavy noise filtering if you go that route. One other possibility is to use an LM329, LM399, or LTZ1000 (in order of increasing performance) as a reference with a scaling amp. Because those references are all ~6.9v, it's best to use an inverting scaling amp to realize 5v or less -- but that is actually good (aside from the bother of needing a negative supply to bias the reference), because you can configure the amp as a multiple-feedback filter and the gain will continue to fall below unity as frequency increases. You need to use a very low noise op-amp (e.g., LT1128), and the feedback resistors must have low values -- which tends to make the required capacitors impractically large if you want significant noise attenuation below 10Hz (also, make sure the op amp has sufficient output current capability to drive the low-resistance feedback loop). It's brute force, but it can work well. 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] TDS12 (AKA PRS10) use indication.
I have a SR TDS12 which apart from name appears to be a PRS10. The ID string indicates PRS10 and the firmware version is the same as on another PRS10 that I have. The only differences that I could see at first power up is the that default config has Lock Mode 2 as opposed to the normal default of 1, and a zero time offset. As I didn’t get my PRS10 new, I do not know if that is normally calibrated when new. Anyhow, it works a charm with unlocked frequency stability in spec. It has a date code of 03 2004 and that and the S/N are newer than the PRS10. Both have firmware version 3.24. The user manual indicates that the FC!? command returns a power cycle count and EEPROM update count in addition to the frequency control values. The FC!? Command may be used to read the value which is stored in the EEPROM. The value stored in EEPROM is used to set the 10 MHz at startup, before the FLL can be established. Occasionally while the unit is operating (at about 20 minutes after power-on and once a day there after) the program will write a new value to EEPROM to correct the value for crystal aging. Example: FC!? will return four values (separated by commas), the number of power cycles the unit has undergone, the number of times the FC pair has been written to EEPROM, and the value of the FC pair (high, low) which is used at turn-on and restart. The same text is in the user manuals V1.1 to the latest, v1.4. I had only just noticed this as while I was finding out how to set the TO value. So I used the count to calculate a rough powered on time. It came to about 12 years which although longish is well within the expected lifetime. I started to track it and found that it is not updated daily as per the manual, but systemtically twice a day. That of course halves the usage time. Unfortunately I have not been able yet to see what my PRS10’s values are as I am still fiddling with the TDS12. So: Can anyone with PRS10s on the bench tell me if they see the same behavior ? Thx ___ 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] Milliren 260-0544-C
Hello! I would like to buy 4 or 5 Milliren 260-0544-C from Excess Solutions as it was discussed 22 october 2014, but their shipping rates are really excessive (127 USD for 4 of them). So I would like to know if there's someone in the US who can buy them for me and ship them cheaply; eventually if there's someone interested in a group buy we can then ask them a discount on the units. Now they have a stock of 39 and sell them 15 USD each. Also I would like to know if there's someone in EU interested to buy the lucent kit so we can buy two (or more) and divide the shipping rates. I can use Euroexpress to ship the goods inside EU and it's cheap enough it would be interesting. Best regards, Andrea ___ 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] June 30 2015 leap second
Tom, Thanks for the comments ! In my design I am using NMEA as an option to set initial time on the clock. Its just faster and more convenient than doing it manually. And in the other (rare) occasions when clock logic could decide to sync. RTC module time with time received from GPS module. Basically I decide not to relay on GPS NMEA too much. My clock using 1PPS signal coming from internal GPS module or from external source connected to the device. That 1PPS and 32kHz signal from RTC module, connected to the MCU timers. So, I know for sure if RTC module generate its 32k signal slower/faster than it should be. If the difference between of those two signals become too big, clock will do autocorrection for the RTC oscillator to trim the value for Aging Register. RTC module has accuracy 2ppm. I think it suppose to keep the time well. Initially I was thinking that GPS will receive hh:59:60 NMEA message and I could use it as it is. But now I think I'll add some more code to handle such wonderful thing as a leap second event. I am going to create subroutines which will allow me to enter and keep leaps second event in battery backed SRAM and apply it as that even occurred. Unfortunately it will need the human interaction to set up leap second events. But if I'll leave the clock logic as it is now, I'll need to correct time on the clock any way. Since 1PPS just keep RTC oscillator in tact. But time on the clock will be 1 second ahead. -- WBW, V.P. ___ 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] June 30 2015 leap second
Tim, I was using perl as a tool to calculate UNIX time. As my project based on STM32 MCU, I have no option to use time libraries. And I dont' think its applcable for my project. I am thinking what exactly of that UNIX time is. Looks like its using simple constants, like we have 86400 seconds per day, we have 365/366 days per year. And we have certain leap years with strict rule to identify it. For the clock to use on a desk, its should be sufficient to avoid confusion with rest of the world. ;-) In the other words, looking to current UNIX time we could identify the current date/time as most people see it. But its give us zero info about actual number of seconds passed since Thursday, 1 January 1970, 00:00:00. Regards, V.P. V.P., since you mention Perl and leap seconds, I'd like to point out that there's a very useful Perl library for computing delta times around leapsecond jumps: http://search.cpan.org/~drolsky/DateTime-1.12/lib/DateTime/LeapSecond.pm [6] This particular library is useful if you need to know the correct delta time between UTC timestamps but have chosen to ignore the ambiguity problem of correctly marking the leapsecond itself. ___ 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] June 30 2015 leap second
I think you can see this as a 15 second jump if you watch a GPS receiver doing a cold start. I mean really cold as in no memory at all rather than it t...@patoka.org said: Exactly ! I saw that behaviour few times.But I was thinking its because of some very old satelites which knows nothing about recent leap seconds send that information to the air. Yeah, I know.. So naive... ;-) I have my T-Bolt running 24x ... Does anybody know the details of the TBolt? Does it have any way to remember the almanac or time without external power? I looked at a few pictures from the net and didn't see anything that looked appropriate, but I didn't pull the cover off mine. A large cap would probably provide a few minutes to hours without using super-cap technology which probably didn't exist when the TBolt was designed or adding nasty chemicals that batteries usually contain. -- 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.
Re: [time-nuts] Milliren 260-0544-C
Are those not the ones that have no EFC In a message dated 1/7/2015 3:02:20 P.M. Eastern Standard Time, erm1ea...@ermione.com writes: Hello! I would like to buy 4 or 5 Milliren 260-0544-C from Excess Solutions as it was discussed 22 october 2014, but their shipping rates are really excessive (127 USD for 4 of them). So I would like to know if there's someone in the US who can buy them for me and ship them cheaply; eventually if there's someone interested in a group buy we can then ask them a discount on the units. Now they have a stock of 39 and sell them 15 USD each. Also I would like to know if there's someone in EU interested to buy the lucent kit so we can buy two (or more) and divide the shipping rates. I can use Euroexpress to ship the goods inside EU and it's cheap enough it would be interesting. Best regards, Andrea ___ 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] Using oscillators to measure earthquakes
Today the Dallas area has been experiencing several eathquakes. The largest were magnitude 3.2, 3.6, and 3.1 at a depth of around 4km.They happened around every three hours. I am around 5 miles from the epicenter. They are strong enough to shake the house quite a bit. The largest put a hairline crack in some sheetrock. After the second one I cobbled up a sensor using an old tight pll type of circuit that I was playing with several years ago, 24 bit A/D, and an AVR based touch-screen microcontroller. I hacked up some quick code to monitor and graph the A/D. Inputs to the circuit were an HP5065 and a rather woogedy 5 MHz OCXO. The oscillator was placed on my garage floor and weighted down with a 2kg calibration weight. Woo hoo! the last quake did produce a measurable signal... Now I have to figure out a way to get the data off the micro-controller... ___ 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] June 30 2015 leap second
I'm not sure there's any computer time package that correctly disambiguates
23:59:59 vs 23:59:60 in UTC timestamps in a general purpose way. Some
software simply rejects 23:59:60 UTC as invalid, some will quietly map it
to 23:59:59 effectively making those two seconds impossible to distinguish.
There are important systems in the world, those that genuinely have to
distinguish between those two seconds, that do all timekeeping in TAI or
GPS timescales instead of UTC. I think the Olsen timezone database/library
does support TAI. I don't know if the Olsen timzone library supports GPS.
V.P., since you mention Perl and leap seconds, I'd like to point out that
there's a very useful Perl library for computing delta times around
leapsecond jumps:
http://search.cpan.org/~drolsky/DateTime-1.12/lib/DateTime/LeapSecond.pm
This particular library is useful if you need to know the correct delta
time between UTC timestamps but have chosen to ignore the ambiguity problem
of correctly marking the leapsecond itself.
The newest announced leap second is not in the table of leapseconds built
into the code yet, but it's a simple matter to add it (cut and paste from
the IPERS).
Tim.
On Tue, Jan 6, 2015 at 4:01 PM, d0ct0r t...@patoka.org wrote:
Hello,
As I am in the process of creation of my own Nixie clocks. And it probably
good time frame to clarify one thing about leap seconds. In my project I am
using GPS module as an option to have current UTC time and also to have
1PPS signal to do auto-adjustment for external RTC module. The question is
how usually GPS modules handle leap seconds ? Is it satelates who send UTC
time to GPS module or GPS module has firmware with leap second information
hard-coded ?
The same question is for UNIX epoch time. How computers knows if it is
necessary to add leap seconds ? Lets say I am using very simple script to
calculate UNIX time for specified date:
#!/usr/bin/perl
use Time::Local;
my ($d, $m, $y);
my $time;
@myYears = ('01/06/2000', '01/06/2015', '01/06/2038', '01/06/3000');
foreach (@myYears) {
($d, $m, $y) = split '/', $_;
$time = timelocal(0,0,0,$d,$m-1,$y);
printf %ld\n\r, $time;
}
==
It will produce the following output:
959832000
1433131200
2158977600
32516740800
I am not sure if its take leap second consideration. Most likely not. And
that means its only accurate for the present and pas time. Right ? For my
clock I already implement the function for the leap second and I am able to
add/remove number of seconds from the time I receiving from GPS or any
other source. But it will be more inetersting if clock could do it
automagically and shows me that famous 60 number without human
interaction. Any advise for this ? Thanks !
Regards,
V.P.
On , Tom Van Baak wrote:
Just announced: there will be a positive leap second at the end of
June 30 2015 UTC (that's Wednesday July 1st for most of the world).
As usual we time nuts will have a leap second party -- where we
capture and share the magic hh:59:60 display on as many different
clocks and instruments as possible.
/tvb
More info:
ftp://hpiers.obspm.fr/iers/bul/bulc/bulletinc.dat
http://hpiers.obspm.fr/eop-pc/
And for those of you who want to know how long each day really is:
ftp://hpiers.obspm.fr/iers/bul/bulb_new/bulletinb.dat
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--
WBW,
V.P.
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