Jim, Getting back to the original question, I'd suggest that the Epson-Toyocom FC-12M would be an appropriate device. See http://ndap3-net.ebz.epson.co.jp/w/www/PDFS/epdoc_qd.nsf/WE_khz_unit/737394E88F20BFBA4925736B002B4C07?OpenDocument. It is a surface mount device, very small, 2 x 1.2 x 0.6mm, and is a true tuning fork, but manufactured using QMEMs (Quartz micro-electro-mechanical, photolithographic techniques). The repeatability achieved by this manufacturing method gives a tightly specified parabolic frequency response (typical of tuning forks) with 25°C turnover temperature.
As others have mentioned, there are plenty of strategies around for managing the temperature control of the reference, most achieved by operating the crystal slightly high, and running a pulse swallower driven by a table or other algorithm. Clearly (as is done in the Dallas device) the closer you can associate the temperature sensor with the crystal, the lower the hysteresis and the better the accuracy. Of course a pulse swallower isn't something you'd use for frequency control, but is quite appropriate for time keeping over days and weeks. I have tested the FC-12M in a low power oscillator (I used the Texas LVC1404 oscillator chip and an LM94022 silicon temperature sensor), and it gave very nice results, no dips or jumps over temperature, and reasonable phase noise (although this isn't an issue with RTCs). I modelled the temperature response in EXCEL and it closely followed the 2nd order model. Regards, Murray Greenman -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Thursday, 27 May 2010 5:31 p.m. To: [email protected] Subject: time-nuts Digest, Vol 70, Issue 75 Send time-nuts mailing list submissions to [email protected] To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to [email protected] You can reach the person managing the list at [email protected] When replying, please edit your Subject line so it is more specific than "Re: Contents of time-nuts digest..." Today's Topics: 1. Re: For your museum only Loran-C monitor (paul swed) 2. Re: IRIG B (jimlux) 3. Re: Digital tight PLL method (Steve Rooke) 4. Re: Digital tight PLL method (J. L. Trantham) 5. Re: Digital tight PLL method (Bob Camp) 6. Re: IRIG B (Robert Atkinson) 7. Most accurate small crystal (Jim Palfreyman) 8. Re: Most accurate small crystal (Brooke Clarke) ---------------------------------------------------------------------- Message: 1 Date: Wed, 26 May 2010 08:44:16 -0400 From: paul swed <[email protected]> Subject: Re: [time-nuts] For your museum only Loran-C monitor To: Discussion of precise time and frequency measurement <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1 Great ? Have to respond later On Wed, May 26, 2010 at 1:27 AM, Hal Murray <[email protected]> wrote: > > [email protected] said: > > Thats why I designed the loran c simulator. It works well. All I need to > do > > is hook it to an antenna and away you go. Maybe a small power amp would > be > > handy. Say 100KW? Antennas the real killer. I think its a zoning problem. > > What's going to happen to that chunk of spectrum? > > How much power/antenna would it take to make a signal that was useful out > to > 1 mile? 100 miles? > > What are the chances the FCC would let amateurs run timing and/or location > services on that band? 1/2 :), but there might be something interesting in > there. > > > > -- > These are my opinions, not necessarily my employer's. I hate spam. > > > > > _______________________________________________ > 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. > ------------------------------ Message: 2 Date: Wed, 26 May 2010 06:16:49 -0700 From: jimlux <[email protected]> Subject: Re: [time-nuts] IRIG B To: Discussion of precise time and frequency measurement <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Bob Camp wrote: > Hi > > Strange as it seems, *stocking* the R's and C's can be an issue. There's also > placement cost. Based on some of the numbers you see, the cross over point > (IC to odd value R's and C's) is amazingly low. I'm not saying any of that's > right, just that it's the way a lot of companies roll up the costs. > > Bob > > Not surprising.. the cost to stock, pick, place, solder is probably the same for a small IC and a R or C. So, the only possible saving would be if the IC is a LOT more expensive than a single or two Rs or Cs. There might be a power dissipation difference, or a temperature range difference that would push you one way or another. ------------------------------ Message: 3 Date: Thu, 27 May 2010 02:50:42 +1200 From: Steve Rooke <[email protected]> Subject: Re: [time-nuts] Digital tight PLL method To: Discussion of precise time and frequency measurement <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1 On 25 May 2010 04:48, WarrenS <[email protected]> wrote: > > Can't beat a simple analog version of ?NIST's "Tight Phase-Lock Loop Method > of measuring Freq stability". > http://tf.nist.gov/phase/Properties/one.htm#oneone ? ?Fig 1.7" I can't seem to access that link, can anyone else? Steve -- Steve Rooke - ZL3TUV & G8KVD A man with one clock knows what time it is; A man with two clocks is never quite sure. ------------------------------ Message: 4 Date: Wed, 26 May 2010 10:06:57 -0500 From: "J. L. Trantham" <[email protected]> Subject: Re: [time-nuts] Digital tight PLL method To: "'Discussion of precise time and frequency measurement'" <[email protected]> Message-ID: <00c701cafce5$16fc8a40$44f59e...@net> Content-Type: text/plain; charset="iso-8859-1" Worked fine for me and very informative. Joe -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Steve Rooke Sent: Wednesday, May 26, 2010 9:51 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Digital tight PLL method On 25 May 2010 04:48, WarrenS <[email protected]> wrote: > > Can't beat a simple analog version of ?NIST's "Tight Phase-Lock Loop Method > of measuring Freq stability". > http://tf.nist.gov/phase/Properties/one.htm#oneone ? ?Fig 1.7" I can't seem to access that link, can anyone else? Steve -- Steve Rooke - ZL3TUV & G8KVD A man with one clock knows what time it is; A man with two clocks is never quite sure. _______________________________________________ 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. ------------------------------ Message: 5 Date: Wed, 26 May 2010 11:58:03 -0400 From: "Bob Camp" <[email protected]> Subject: Re: [time-nuts] Digital tight PLL method To: "'Discussion of precise time and frequency measurement'" <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset="iso-8859-1" Hi Works from here. It's a very brief description of pretty much every way in the world to measure frequency. Bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Steve Rooke Sent: Wednesday, May 26, 2010 10:51 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Digital tight PLL method On 25 May 2010 04:48, WarrenS <[email protected]> wrote: > > Can't beat a simple analog version of ?NIST's "Tight Phase-Lock Loop Method > of measuring Freq stability". > http://tf.nist.gov/phase/Properties/one.htm#oneone ? ?Fig 1.7" I can't seem to access that link, can anyone else? Steve -- Steve Rooke - ZL3TUV & G8KVD A man with one clock knows what time it is; A man with two clocks is never quite sure. _______________________________________________ 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. ------------------------------ Message: 6 Date: Wed, 26 May 2010 20:17:02 +0000 (GMT) From: Robert Atkinson <[email protected]> Subject: Re: [time-nuts] IRIG B To: Discussion of precise time and frequency measurement <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=iso-8859-1 A good example is the good old 555 timer. A cmos 55 is 41 cents and needs a timing cap and resistor. A pic10f200 is 31 cents and needs no support components. You can also do fancy timing with the pic. I hate to say it but there is really no contest once you have the tools (free complier and a programmer for <$50). Just a shame it's killing analog skills. ? Robert G8RPI.? --- On Wed, 26/5/10, jimlux <[email protected]> wrote: From: jimlux <[email protected]> Subject: Re: [time-nuts] IRIG B To: "Discussion of precise time and frequency measurement" <[email protected]> Date: Wednesday, 26 May, 2010, 14:16 Bob Camp wrote: > Hi > > Strange as it seems, *stocking* the R's and C's can be an issue. There's also > placement cost. Based on some of the numbers you see, the cross over point > (IC to odd value R's and C's) is amazingly low. I'm not saying any of that's > right, just that it's the way a lot of companies roll up the costs. > Bob > > Not surprising.. the cost to stock, pick, place, solder is probably the same for a small IC and a R or C.? So, the only possible saving would be? if the IC is a LOT more expensive than a single or two Rs or Cs. There might be a power dissipation difference, or a temperature range difference that would push you one way or another. _______________________________________________ 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. ------------------------------ Message: 7 Date: Thu, 27 May 2010 14:22:18 +1000 From: Jim Palfreyman <[email protected]> Subject: [time-nuts] Most accurate small crystal To: Discussion of precise time and frequency measurement <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1 Hi All, I have a RSA SecurID device which I use to log in to my work's VPN. For those of you not familiar with these, they show you a 6 digit number that you use (combined with a PIN) to log in. This number changes every minute. The changing of this number lines up with the servers at the other end and, as I understand it, they do take into account gradual drift. These devices have a limited programmed lifetime of three years as well. So the internal clock on one of these needs to be decent. I have timed the accuracy of this internal clock and have found it to be pretty good so far. 17 days ago it was ticking over at 21.8 sec past the minute and a quick visual inspection today and it was still *very* close to that. I will confirm it properly tonight. Now this device travels around with me, like a wristwatch, but is not on my person. It is usually in my laptop bag. So it is subject to quite varying temperatures. So it's been nearly 3 weeks and this device has barely changed 0.1 to 0.2 secs tops. Now that's not bad compared to digital watches. I presume it has a quartz crystal in it, obviously no oven, but my question is: What is the best crystal you can get on the market today that would work in a watch type device with very little power available? What's the best accuracy that can be expected? I know straight out of the factory they can be pretty spot on (as my Casio G Shock was) but it has aged markedly and now gains a couple of seconds a week. So what is the best we can expect long term too? Regards, Jim Palfreyman ------------------------------ Message: 8 Date: Wed, 26 May 2010 22:30:36 -0700 From: Brooke Clarke <[email protected]> Subject: Re: [time-nuts] Most accurate small crystal To: Discussion of precise time and frequency measurement <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Hi Jim: The last time I looked into this it was the DS3231 (now part of Maxim). See the live demo: http://www.maxim-ic.com/products/timers/DS3231_demo/ Have Fun, Brooke Clarke http://www.PRC68.com Jim Palfreyman wrote: > Hi All, > > I have a RSA SecurID device which I use to log in to my work's VPN. For > those of you not familiar with these, they show you a 6 digit number that > you use (combined with a PIN) to log in. This number changes every minute. > The changing of this number lines up with the servers at the other end and, > as I understand it, they do take into account gradual drift. These devices > have a limited programmed lifetime of three years as well. So the internal > clock on one of these needs to be decent. > > I have timed the accuracy of this internal clock and have found it to be > pretty good so far. 17 days ago it was ticking over at 21.8 sec past the > minute and a quick visual inspection today and it was still *very* close to > that. I will confirm it properly tonight. > > Now this device travels around with me, like a wristwatch, but is not on my > person. It is usually in my laptop bag. So it is subject to quite varying > temperatures. > > So it's been nearly 3 weeks and this device has barely changed 0.1 to 0.2 > secs tops. Now that's not bad compared to digital watches. > > I presume it has a quartz crystal in it, obviously no oven, but my question > is: > > What is the best crystal you can get on the market today that would work in > a watch type device with very little power available? What's the best > accuracy that can be expected? > > I know straight out of the factory they can be pretty spot on (as my Casio G > Shock was) but it has aged markedly and now gains a couple of seconds a > week. So what is the best we can expect long term too? > > Regards, > > Jim Palfreyman > _______________________________________________ > 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] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts End of time-nuts Digest, Vol 70, Issue 75 ***************************************** _______________________________________________ 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.
