Graham, I think that is the real challenge here: most folks don't know what "precise" means for them. Timing is such a novel technology that most folks are amazed that we are trying to get parts per trillion (or better) accuracy and stability! We get customers all the time that want very precise timing, very good phase noise, and overall very good performance but are only used to TCXO's with maybe 10ppm frequency accuracy and cannot specify anything beyond that. The challenge is to explain the cost-benefit to them, like: 1ppm == $1 0.01ppm = $300 10ppt == $1500 0.1ppt == $$$ etc. Once dollars are mentioned, desired specifications usually are attained at fairly quickly :) We recently had an inquiry that we forwarded to a major atomic oscillator vendor, and the estimated $10 Million design cost and 10 year design time quickly shut that idea down.. bye, Said In a message dated 7/12/2014 08:54:09 Pacific Daylight Time, gh78731@gmail.com writes: Shane: The question I think that is being asked is ... What does "precise" mean to you? To the nearest order of magnitude, what kind of accuracy are you looking for on your three signals. This defines the kind of system you will need. This group normally aspires to the more accurate end of the scale. If you are doing simple time logging of some process, then you are probably at the other end of the possible accuracy scale, and can do things much more simply and cheaply. So ... 1 PPS: +/- 1 ns? 10 ns? 100 ns? 1 us? 10 us ? NTP: +/- 10 ms? 100 ms? 1 second? 10 MHz: +/- 10E-6? 10E-9? 10E-12? 10E-14? --- Graham == On Sat, Jul 12, 2014 at 3:57 AM, Shane Morris <edgecomberts@gmail.com> wrote: > Hal, > > As much as I'd like to explain the "big picture" in list, it would make God > awful noise - if you wish to know any details, I encourage you to respond > to me off list. Given the fact that the robotics is so totally off topic, > I'm not willing to discuss them here. Thats only out of respect to the > topic of the list. The only real stipulations at this design part of the > project is 10MHz out, 1PPS out, and NTP out. Please don't think I'm being > narqy, I'm really not going to pollute the list with off topic chatter. I > am more than happy to discuss off list, as and when. > > David, > > I was planning to use RaspberryPis in some part of the network, and of > course, I must be silly, they have ethernet, and can run Real Time Linux > (the LinuxCNC distros that have been made for control of CNC machines). By > the way, the whole network uses heterogeneous CPU types, I'm pretty > agnostic to CPU type, as long as it does the job I need it to. The actual > ethernet interface won't be as deterministic as we'd like, being chained to > the USB bus, but if one was not to put any other USB devices on, nor attach > anything that draws power, the USB performance would be good enough for > second accuracy NTP frames. This is without any real analysis of any spec > sheets, although I have this link: > > http://www.synclab.org/?tag=raspberry%20pi > > Thats an interesting read in and of itself. An additional link is: > > http://www.geekroo.com/products/795 > > Which is a Mini ITX motherboard for RaspberryPi, which can then go nicely > into a 1RU case. Add LCDs and other bits and bobs as needed (I saw a nice > little LCD with an ATMega driver taking TTY strings in the ODROID Magazine > earlier today - it was meant for an ODROID, but it will work with anything > that'll output VT100 codes). Once in an 1RU case, it looks neat, and would > work just as well as a $500 NTP ethernet time source second hand off eBay, > if not much more configurable and hackable. > > Many thanks for the thoughts! > > Shane. > > > On Sat, Jul 12, 2014 at 5:50 PM, Hal Murray <hmurray@megapathdsl.net> > wrote: > > > > > edgecomberts@gmail.com said: > > > I am needing a GPS source of precise time, in three flavours - 10MHz > (or > > > so), 1PPS, and ethernet NTP. In the beginning, the NTP will be most > > > important, and as time goes on, I'll need the 1PPS signal. > > ... > > > If a static CW12-TIM ethernet clock could be made, I would be willing > to > > try > > > my hand at mounting them to mobile robots, again, for synchronised > > timing of > > > events. > > > > I'm missing the big picture. Are the robots the end target? What are > you > > going to do before that? > > > > Do the robots have a network connection? (maybe only WiFi to a local PC > > controlling them) > > > > How accurately do the robots have to be synchronized? > > > > > > -- > > 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 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.

Said, ... and deprive us from cheap surplus oscillators of good performance? What where you thinking? :) But I agree fully with your point, people don't understand how their poorly speced requirements translate into cost and design-time. Accurate time to the fs for no budget is what you can expect if they push their wishlist, but they have seen the E-18 numbers in some fancy article, so as is now possible. I think not (mixing time and frequency numbers is just what you can expect among other things). Also, ADEV numbers isn't everything, it can be a splendid answer to the incomplete and incorrect asked question. Cheers, Magnus On 07/12/2014 10:44 PM, SAIDJACK@aol.com wrote: > Graham, > > I think that is the real challenge here: most folks don't know what > "precise" means for them. Timing is such a novel technology that most folks are > amazed that we are trying to get parts per trillion (or better) accuracy and > stability! > > We get customers all the time that want very precise timing, very good > phase noise, and overall very good performance but are only used to TCXO's with > maybe 10ppm frequency accuracy and cannot specify anything beyond that. > > The challenge is to explain the cost-benefit to them, like: > > 1ppm == $1 > 0.01ppm = $300 > 10ppt == $1500 > 0.1ppt == $$$ etc. > > Once dollars are mentioned, desired specifications usually are attained at > fairly quickly :) > > We recently had an inquiry that we forwarded to a major atomic oscillator > vendor, and the estimated $10 Million design cost and 10 year design time > quickly shut that idea down.. > > bye, > Said > > > In a message dated 7/12/2014 08:54:09 Pacific Daylight Time, > gh78731@gmail.com writes: > > Shane: > > The question I think that is being asked is ... > What does "precise" mean to you? > To the nearest order of magnitude, what kind of accuracy are you looking > for > on your three signals. This defines the kind of system you will need. > > This group normally aspires to the more accurate end of the scale. > > If you are doing simple time logging of some process, then you are > probably at the other end of the possible accuracy scale, and can > do things much more simply and cheaply. > > So ... > > 1 PPS: +/- 1 ns? 10 ns? 100 ns? 1 us? 10 us ? > NTP: +/- 10 ms? 100 ms? 1 second? > 10 MHz: +/- 10E-6? 10E-9? 10E-12? 10E-14? > > --- Graham > > == > > > On Sat, Jul 12, 2014 at 3:57 AM, Shane Morris <edgecomberts@gmail.com> > wrote: > >> Hal, >> >> As much as I'd like to explain the "big picture" in list, it would make > God >> awful noise - if you wish to know any details, I encourage you to respond >> to me off list. Given the fact that the robotics is so totally off topic, >> I'm not willing to discuss them here. Thats only out of respect to the >> topic of the list. The only real stipulations at this design part of the >> project is 10MHz out, 1PPS out, and NTP out. Please don't think I'm being >> narqy, I'm really not going to pollute the list with off topic chatter. I >> am more than happy to discuss off list, as and when. >> >> David, >> >> I was planning to use RaspberryPis in some part of the network, and of >> course, I must be silly, they have ethernet, and can run Real Time Linux >> (the LinuxCNC distros that have been made for control of CNC machines). > By >> the way, the whole network uses heterogeneous CPU types, I'm pretty >> agnostic to CPU type, as long as it does the job I need it to. The actual >> ethernet interface won't be as deterministic as we'd like, being chained > to >> the USB bus, but if one was not to put any other USB devices on, nor > attach >> anything that draws power, the USB performance would be good enough for >> second accuracy NTP frames. This is without any real analysis of any spec >> sheets, although I have this link: >> >> http://www.synclab.org/?tag=raspberry%20pi >> >> Thats an interesting read in and of itself. An additional link is: >> >> http://www.geekroo.com/products/795 >> >> Which is a Mini ITX motherboard for RaspberryPi, which can then go nicely >> into a 1RU case. Add LCDs and other bits and bobs as needed (I saw a nice >> little LCD with an ATMega driver taking TTY strings in the ODROID > Magazine >> earlier today - it was meant for an ODROID, but it will work with > anything >> that'll output VT100 codes). Once in an 1RU case, it looks neat, and > would >> work just as well as a $500 NTP ethernet time source second hand off > eBay, >> if not much more configurable and hackable. >> >> Many thanks for the thoughts! >> >> Shane. >> >> >> On Sat, Jul 12, 2014 at 5:50 PM, Hal Murray <hmurray@megapathdsl.net> >> wrote: >> >>> >> > edgecomberts@gmail.com said: >>>> I am needing a GPS source of precise time, in three flavours - 10MHz >> (or >>>> so), 1PPS, and ethernet NTP. In the beginning, the NTP will be most >>> > important, and as time goes on, I'll need the 1PPS signal. >>> ... >>>> If a static CW12-TIM ethernet clock could be made, I would be willing >> to >>> try >>>> my hand at mounting them to mobile robots, again, for synchronised >>> timing of >>>> events. >>> >>> I'm missing the big picture. Are the robots the end target? What are >> you >>> going to do before that? >>> >>> Do the robots have a network connection? (maybe only WiFi to a local > PC >> > controlling them) >>> >>> How accurately do the robots have to be synchronized? >>> >>> >>> -- >> > 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 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. >