Re: [time-nuts] PC time app
On 11/25/11 9:56 PM, Steve . wrote: I'm curious as to what folks are doing with PC's that require micro second accuracy for days or weeks or what have you. Any examples? not microseconds, but milliseconds... Running multi-day tests in a spacecraft testbed where you've got PC-based test equipment logging data. Typical PC clock errors of 50-100 ppm is seconds in a day... ___ 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] PC time app
On Fri, Nov 25, 2011 at 9:56 PM, Steve . iteratio...@gmail.com wrote: I'm curious as to what folks are doing with PC's that require micro second accuracy for days or weeks or what have you. The way you get the reliability is easy, it just cost money. You set up multiple servers each with its own GPS receiver. I have a Intel Atom powered mainboard. I looked around and found one that did not have a fan on the heat sink. These use much less power, I I hopped made less heat Without the heat there is also no thermal management so it is stable. I installed Linux and connected a Motorolla Oncore GPS. These GPSes have the PPS running at about 60nS, 1 sigma. On NTP I've not been above to get down to single uS. Seem to be running at the dozen or so uS level. My guess is the next is to unsolder the crystal oscillator from the main board and replace it with something better. Likely a TCXO. That should help be more then one order of magnitude. -- 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.
Re: [time-nuts] PC time app
On 25 Nov, 2011, at 21:56 , Steve . wrote: I'm curious as to what folks are doing with PC's that require micro second accuracy for days or weeks or what have you. Any examples? Curious, Steve I have a PCI-X board with an FPGA which implements a clock running at 320 MHz. The 320 MHz can be phase-locked to an external 5 or 10 MHz frequency input, and the card also has 4 PPS inputs. A transition on a PPS input causes the FPGA to record a timestamp, with a precision of not quite 3 ns, and deliver it to software via an interrupt. The 10 MHz and PPS outputs from my GPS receiver are synchronous, so once the board clock is set it keeps the time of the GPS receiver without any further adjustment. The system (the OS is NetBSD, but with the kernel timekeeping replaced) computes its time as a linear function of the CPU's cycle counter, which on my machines seems to run at a constant 2.4 GHz. I can get a sample timestamp (actually a pair for them, the board-computer time comparison mechanism is the trickiest part of the design) from the FPGA by doing a load from a card register, so an 'rdtsc; load; rdtsc' gives me a sample offset between the computer's clock and the card's clock with a constant systematic error which (arguably) should be less than +/- 10 ns and with the board's precision of about 3 ns. I get sample offsets at randomly jittered intervals which average to about 0.25 seconds, so I get about 4 offsets per second with about 3 ns of round-off noise. The processing of these reduces to a linear least squares fit (the y-value is the offset, the x-value is the time of the sample with respect to the computer's clock) after some sanity filtering. The least squares fit gives me a frequency error and a time offset error, along with confidence intervals for each. I adjust the computer's clock when either the frequency error or the time offset becomes non-zero with 80% confidence. Typically I find the result of this to be, very roughly, a clock adjustment every 10 seconds, with a frequency adjustment on the order of 10^-9 and a time adjustment on the order of 10 ns. This is not perfectly reliable, of course; if I leave the cover off the computer and cold-spray the computer's innards I can drive the clock crazy, so it depends on temperature variations inside the case being modest, or at least occurring relatively slowly compared to my offset sample rate. When left alone in a rack in a quiet room, however, I seldom see anything bad happening, so I think it isn't dangerous to assert that the arrangement is typically keeping the computer's clock within +/- 20 ns of the GPS receiver, with worst case excursions being no worse than maybe +/- 50 ns. This has a number of uses, but is particularly good for NTP and PTP development. You can use a board in server synchronize the server's system clock to a GPS receiver, and then use a board tracking the same GPS receiver in a client machine to independently measure how well the software is managing the client machine's clock. This avoids having the NTP or PTP software grade its own homework. Dennis Ferguson ___ 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] PC time app
Just redoing a PC in the shop. Don't know if I've suggested a program called NMEATime to the nuts. I've had this program running on everything from Win2k to Win7, no hitches. It will sync the PC clock to either a GPS or to a network signal, at a chooseable update period. Highly recommended and right now available for $15.00 through Paypal. A bargain IMHO. I have nothing to do with those that bring you the program. Don -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. R. Bacon 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.
Re: [time-nuts] PC time app
Good old nema time. Indeed I started using it on win98 or was it 95?? Way back is the right answer. In fact I have a very old laptop that essentially runs just that program. It also generates time codes. IRIG B as I recall and thats what really made it useful. Good top know they are still around and $15 is cheap. Thanks Paul WB8TSL On Fri, Nov 25, 2011 at 5:01 PM, Don Latham d...@montana.com wrote: Just redoing a PC in the shop. Don't know if I've suggested a program called NMEATime to the nuts. I've had this program running on everything from Win2k to Win7, no hitches. It will sync the PC clock to either a GPS or to a network signal, at a chooseable update period. Highly recommended and right now available for $15.00 through Paypal. A bargain IMHO. I have nothing to do with those that bring you the program. Don -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. R. Bacon 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. ___ 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] PC time app
I have a copy and I like it, however you can just set your system scheduler to update your clock more often. Win 7 is 1x a week out of the box but it's easy enough to set to once every 15 minutes if you want. It's also free. http://answers.microsoft.com/en-us/windows/forum/windows_7-windows_programs/windows-7-time-sync-runs-update-weekly-how-do-i/3ad0278b-370d-416d-867a-534729ca7d32 -Bob On Fri, Nov 25, 2011 at 3:01 PM, Don Latham d...@montana.com wrote: Just redoing a PC in the shop. Don't know if I've suggested a program called NMEATime to the nuts. I've had this program running on everything from Win2k to Win7, no hitches. It will sync the PC clock to either a GPS or to a network signal, at a chooseable update period. Highly recommended and right now available for $15.00 through Paypal. A bargain IMHO. I have nothing to do with those that bring you the program. Don -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. R. Bacon 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. ___ 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] PC time app
Yeah. I just found out that my XP and 7 systems can do this update. Red face! Just goes to show ya. Don Robert Darlington I have a copy and I like it, however you can just set your system scheduler to update your clock more often. Win 7 is 1x a week out of the box but it's easy enough to set to once every 15 minutes if you want. It's also free. http://answers.microsoft.com/en-us/windows/forum/windows_7-windows_programs/windows-7-time-sync-runs-update-weekly-how-do-i/3ad0278b-370d-416d-867a-534729ca7d32 -Bob On Fri, Nov 25, 2011 at 3:01 PM, Don Latham d...@montana.com wrote: Just redoing a PC in the shop. Don't know if I've suggested a program called NMEATime to the nuts. I've had this program running on everything from Win2k to Win7, no hitches. It will sync the PC clock to either a GPS or to a network signal, at a chooseable update period. Highly recommended and right now available for $15.00 through Paypal. A bargain IMHO. I have nothing to do with those that bring you the program. Don -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. R. Bacon 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. ___ 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. R. Bacon 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.
[time-nuts] PC time app
If you have a Thunderbolt, Lady Heather will sync your time for free... It can sync the time via a keyboard command (TS) or via command line options on a regular basis, or whenever the system clock and GPS clock differ by a given amount. You can specify the inherent delay between the Tbolt time messages and actual time (default 45 milliseconds).It's not a fancy pants NTP, but can typically keep your system clock within a few (20?) milliseconds. --- Good top know they are still around and $15 is cheap. ___ 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] PC time app
Dunno. Does the NMEA driver work on the Meinberg NTP for Windows? Yes, although from some GPS devices the jitter may be worse than from Internet servers (depending on your connection). Given that NTP is free, works extremely well, is well documented, and can be monitored and managed remotely, I don't see why you would want to pay for program which doesn't work as well. I've written some basic notes on installing on Windows here: http://www.satsignal.eu/ntp/setup.html Cheers, 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.
Re: [time-nuts] PC time app
On Fri, Nov 25, 2011 at 9:24 PM, David J Taylor david-tay...@blueyonder.co.uk wrote: Dunno. Does the NMEA driver work on the Meinberg NTP for Windows? Yes, although from some GPS devices the jitter may be worse than from Internet servers (depending on your connection). Given that NTP is free, works extremely well, is well documented, and can be monitored and managed remotely, I don't see why you would want to pay for program which doesn't work as well. That is what every Linux user says about Windows. But it's worse than just not working as well jumping the clock is a defective design. Any software that periodically sets the clock will break a lot of other software that tries to measure time intervals. It is simple: The way to meaue a time interval is to sample the clock, do something, then sample the clock gain. then subtract the first time from the last and then you know how long it took to do that something.Setting the clock periodically breaks this. The only thing that can work is to adjust the clock RATE by tiny amounts Now if you only need enough accuracy so that you are not late to appointments then just do whatever. But we assume on a time nuts list that we care about milli and micro seconds at least 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.
Re: [time-nuts] PC time app
I'm curious as to what folks are doing with PC's that require micro second accuracy for days or weeks or what have you. Any examples? Curious, Steve On Sat, Nov 26, 2011 at 12:50 AM, Chris Albertson albertson.ch...@gmail.com wrote: On Fri, Nov 25, 2011 at 9:24 PM, David J Taylor david-tay...@blueyonder.co.uk wrote: Dunno. Does the NMEA driver work on the Meinberg NTP for Windows? Yes, although from some GPS devices the jitter may be worse than from Internet servers (depending on your connection). Given that NTP is free, works extremely well, is well documented, and can be monitored and managed remotely, I don't see why you would want to pay for program which doesn't work as well. That is what every Linux user says about Windows. But it's worse than just not working as well jumping the clock is a defective design. Any software that periodically sets the clock will break a lot of other software that tries to measure time intervals. It is simple: The way to meaue a time interval is to sample the clock, do something, then sample the clock gain. then subtract the first time from the last and then you know how long it took to do that something.Setting the clock periodically breaks this. The only thing that can work is to adjust the clock RATE by tiny amounts Now if you only need enough accuracy so that you are not late to appointments then just do whatever. But we assume on a time nuts list that we care about milli and micro seconds at least 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] PC time app
On Fri, Nov 25, 2011 at 9:24 PM, David J Taylor david-tay...@blueyonder.co.uk wrote: Dunno. Does the NMEA driver work on the Meinberg NTP for Windows? Yes, although from some GPS devices the jitter may be worse than from Internet servers (depending on your connection). Given that NTP is free, works extremely well, is well documented, and can be monitored and managed remotely, I don't see why you would want to pay for program which doesn't work as well. That is what every Linux user says about Windows. G - but if Linux doesn't run the software you need to run . But it's worse than just not working as well jumping the clock is a defective design. Any software that periodically sets the clock will break a lot of other software that tries to measure time intervals. It is simple: The way to meaue a time interval is to sample the clock, do something, then sample the clock gain. then subtract the first time from the last and then you know how long it took to do that something.Setting the clock periodically breaks this. The only thing that can work is to adjust the clock RATE by tiny amounts Now if you only need enough accuracy so that you are not late to appointments then just do whatever. But we assume on a time nuts list that we care about milli and micro seconds at least Chris Albertson Redondo Beach, California .. and just to be clear, NTP does its best to use RATE adjustments, and avoid stepping the clock (except when the system is first booted). It's other software which may step rather than rate adjust. Cheers, 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.
Re: [time-nuts] PC time app
I'm curious as to what folks are doing with PC's that require micro second accuracy for days or weeks or what have you. Any examples? Curious, Steve I hear of folks measuring time delay of off-air radio signals, where millisecond accuracy is required. Data from multiple receivers in multiple locations is compared. You need good accuracy for geolocating weather satellite data - one second timing error can result in a 7 km location error, so orbit prediction accuracy comes into that as well. It's a similar requirement when pointing a narrow beamwidth antenna at a distant satellite - note that they had to add a wider beamwidth antenna to one of the ESA dishes trying to talk to the Phobos-Grunt probe recently. Milliseconds suits me, though. Cheers, 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.
Re: [time-nuts] PC time app
david-tay...@blueyonder.co.uk said: Yes, although from some GPS devices the jitter may be worse than from Internet servers (depending on your connection). I've been looking for good, low cost GPS gizmos, preferably with no soldering required. If anybody finds one, please let me/us know. The best I've found is the Garmin GPS-18x. It is only good if you can use the PPS signal and it requires some soldering. All the low cost GPS unit's I've tested have horrible jitter. They are crappy without PPS support. In particular, the USB units don't have anything like PPS. I'd call them good-enough if they worked as well as I hope. The USB jitter is not a problem, at least for some/many people. It's small relative to network delays. I'd consider a USB device good enough to be interesting if it worked as expected. The problem isn't just jitter, it's wander. By that I mean very low frequency that's hard to filter out. Ballpark number is 25 ms of jitter and 100 ms of wander. These are from SiRF chips on USB: http://www.megapathdsl.net/~hmurray/bb/gps/Holux-2.png http://www.megapathdsl.net/~hmurray/bb/gps/BU-353-gpgga.png The older Garmin GPS-18 (non x) was good enough. (but, unfortunately, not as sensitive and no longer available) http://www.megapathdsl.net/~hmurray/ntp/GPS18USB-off.gif On the network I have a 384K DSL line. It's mostly idle. ntpd has no trouble filtering out the occasional poor samples when it happens to collect data while I'm loading a big web page. On the other hand, I occasionally download CDs or such. That takes hours. That ties up the line for long enough so that the queuing delays can confuse ntpd. I've seen delays of 3.5 seconds. There is a bufferbloat project working on that area, but it's going to be a lot of work. http://www.bufferbloat.net/ It's screwing things like VoIP. If/when it gets fixed (or even improved) timkeeping will get better for free. -- These are my opinions, not necessarily my employer's. 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] PC time app
I'm curious as to what folks are doing with PC's that require micro second accuracy for days or weeks or what have you. Any examples? The obvious one is you can be a real time nut. :) With a good clock, you can measure network delays. The normal way that ntp works is to exchange packets with a server. That gives you 4 time stamps: the time the request left the client the time the request arrived the server the time the response left the server the time the response arrived the client ntp assumes the network delays in each direction are the same and adjusts the local clock to get that answer. (that's after lots of filtering and such) If instead, you assume that both clocks are good, you can directly calculate the transit time in each direction. If you are going 1000 miles, 1 ms accuracy is probably good enough. If you are interested in LAN distances you probably need better than that. -- These are my opinions, not necessarily my employer's. 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] PC time app
From: Hal Murray Sent: Saturday, November 26, 2011 6:58 AM To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] PC time app david-taylor said: Yes, although from some GPS devices the jitter may be worse than from Internet servers (depending on your connection). I've been looking for good, low cost GPS gizmos, preferably with no soldering required. If anybody finds one, please let me/us know. The best I've found is the Garmin GPS-18x. It is only good if you can use the PPS signal and it requires some soldering. All the low cost GPS unit's I've tested have horrible jitter. They are crappy without PPS support. [] I do agree with Hal's comments. The one other unit I've found is this one, which I know I've mentioned here before: http://www.satsignal.eu/ntp/Sure-GPS.htm but again some assembly is required, including soldering. It can take its power from a spare USB port. I did test the GPS 18(x) with a USB to serial adapter, and the PPS/DCD line was passed through, allowing NTP to work rather better than pure LAN sync, but not as good as a direct connection to the serial port DCD line. Not all USB/serial adapters and their drivers work as well. Cheers, 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.
Re: [time-nuts] PC time
Hi Actually it's a double oven (of course that starts to bleed over to another thread). I also have a bunch of boards running with single ovens ... I *know* I'm not the only one on the list doing this. Bob On Nov 25, 2009, at 8:35 PM, Jeffrey Pawlan wrote: On Wed, 25 Nov 2009, Bob Camp wrote: Hi Doesn't everybody run OCXO's for the clock in their PC? Bob you should make one of those text displays on the bottom of your email that reads: my PC clock is controlled by an HP10811 That distinguishes Time-Nuts members from the general public. ___ 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] PC time
On Wed, 25 Nov 2009, Bob Camp wrote: Hi Doesn't everybody run OCXO's for the clock in their PC? Bob you should make one of those text displays on the bottom of your email that reads: my PC clock is controlled by an HP10811 That distinguishes Time-Nuts members from the general public. ___ 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.
