Er, rather, add 7 hours. You get the idea. On Tue, Nov 30, 2010 at 6:10 PM, Robert Darlington <[email protected]>wrote:
> Hi Greg (and everyone!) > > The environment will be dusty and hot and cold and hot and cold... There > will be air conditioning but probably not much in the way of filtering. > Diesel and gas generators run out of fuel, UPS's are probably not going to > be going along with our stuff since they're too heavy. I'm actually pretty > concerned about the heat issue getting out of control and we were kidding at > work about spontaneous fusion reactions due to the power density. Our #1 > problem with this project has been time synchronization. Most of the big > issues were worked out but sometimes still crop up. The really big issue we > see over and over is when people timestamp data and send that data into our > server, the timestamp doesn't meet our spec. We require time in "UNIX time" > in whole numbers of seconds and assume UTC. You'd be surprised at how many > months have passed since we first realized people were sending us time in > miliseconds so all dates looked like they were 40,000 years in the future. > Our computers are good but we don't have anywhere near that kind of > predictive capability. The next big issue was when a sensor or some other > device sends the data to an intermediary that sends the data to us. More > times than not there is a timezone correction done twice. The sensor will > send in UTC and somebody will subtract 7 hours to put it into UTC again. > They're still doing this from time to time. I recommended we modify our > message protocol to include a timezone offset to force people to think about > it but that opens a whole other can of worms. Do you do it in seconds or > minutes or hours and introduce a whole other potential where people send in > the wrong format? > > Guys, I think I have everything I need now -at least when it comes to > mobile time serving. I really appreciate the responses. Thank you. > > -Bob > > > On Tue, Nov 30, 2010 at 5:35 PM, Greg Dowd <[email protected]> wrote: > >> Rob, you wound me :-) Actually, the Meinberg unit is a great box. The >> commercial devices pretty much all fit the need that you describe. One >> caution I would make about them is the note about the environmentals. >> From experience I can tell you that a HV is a very harsh environment for >> shock and vib that could, and probably does, sometimes exceed the spec >> on these boxes. For a box that has to survive repeated power cycles, >> dusty conditions with limited airflow and unmanned operation, the >> commercial boxes are optimal but can still have issues. For OP, Rb in >> these devices is primarily targeted at holdover, providing extended >> periods of NTP service when the input time source (e.g. GPS) is lost. >> It doesn't sound like this is a requirement for your application. >> >> -----Original Message----- >> From: [email protected] [mailto:[email protected]] On >> Behalf Of Rob Kimberley >> Sent: Tuesday, November 30, 2010 7:55 AM >> To: 'Discussion of precise time and frequency measurement' >> Subject: Re: [time-nuts] OT: NTP server questions >> >> FWIW, you can't go wrong with Meinberg. >> >> Several versions to choose from, reliable, and priced well. >> >> Rob Kimberley >> >> -----Original Message----- >> From: [email protected] [mailto:[email protected]] On >> Behalf Of Robert Darlington >> Sent: 30 November 2010 2:47 PM >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] OT: NTP server questions >> >> Basically I need something to provide time within one second. I can't >> roll >> my own in this case. At home I have a Soekris box with a custom built >> gps >> board for my normal level of time-nuttery but this is not for home. I'm >> looking for commercially made rack mount servers that will not have >> Internet >> access for reference and will need to rely on gps. The system will >> need to >> serve time to less than 100 systems but it will live in a nasty >> environment >> in the back of a humvee (or something like an S-250 electronics >> enclosure) >> with no air conditioning of any sort. I'm currently looking at >> Symmetricom, >> Trimble NetRS, EndRun, and Meinberg. >> >> Also, I apologize if I'm breaching protocol with this thread. This is >> just >> about the first post I ever saw on this list that didn't get a steady >> stream >> of replies. I was actually questioning if this even made it into the >> list >> till I saw this reply. Yes this is for work and I could really use some >> opinions on this stuff since dropping $4-6k isn't in my nature to do at >> home >> for a network clock so I never gave this thought before. >> >> Thanks again, >> Bob >> >> >> On Mon, Nov 29, 2010 at 11:39 PM, Chris Albertson >> <[email protected] >> > wrote: >> >> > What do you need to do? What precision is required and how many >> > clients will >> > you be serving. For most "normal" uses you don't need a special >> purpose >> > server system. A $600 notebook PC and any GPS unit with a serial >> > connection and a copy of Linux or BSD. >> > >> > On Mon, Nov 29, 2010 at 11:36 AM, Robert Darlington >> > <[email protected]> wrote: >> > > Hi guys, >> > > >> > > I'm looking to buy an NTP server for a field deployable server >> > > system. I currently have a Symmetricom SyncServer S250 which does >> more >> than I need. >> > I >> > > am considering buying an S200 (same as the S250 but without the >> > > ability >> > to >> > > connect to an external frequency standard). My gut feeling is I >> > > don't >> > need >> > > a rubidium oscillator or even an OCXO internally since we'd be going >> >> > > from >> > a >> > > power on to being used state in under an hour, outside of any kind >> > > of temperature controlled environment. Are there any manufacturers >> > > out >> > there >> > > besides Symmetricom that I should be looking at for something like >> this? >> > > The unit we're considering buying is about $4k new and is inside of >> > > our budget. >> > > >> > > Thanks, >> > > Bob >> > > _______________________________________________ >> > > time-nuts mailing list -- [email protected] To unsubscribe, go to >> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> > > and follow the instructions there. >> > > >> > >> > >> > >> > -- >> > ===== >> > Chris Albertson >> > Redondo Beach, California >> > >> > _______________________________________________ >> > time-nuts mailing list -- [email protected] To unsubscribe, go to >> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> > and follow the instructions there. >> > >> _______________________________________________ >> time-nuts mailing list -- [email protected] To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
