Re: [time-nuts] New precision watch
Why don't they build a watch that measures the temperature and every time you accurately set it, it adds to a small database of time change v temperature and then adjusts itself internally. Over time it would become quite accurate I would think. Jim On 20 December 2011 11:12, Chuck Harris cfhar...@erols.com wrote: Looking at the datasheet for the DS3232, it doesn't appear that they mean for it to run off of a small coin cell in a watch. Its battery operating capability is purely to keep it running when the main power is turned off. I would suspect that the DS3232's power consumption is due to its being able to drive sizable loads on its various pins. There is nothing inherent in temperature correcting a clock that should take significantly more power than would be used in a normal watch chip. Measuring the temperature would be the most power hungry operation, I would suspect... but fortunately that doesn't have to be done all that often, perhaps once per minute. After the temperature is measured, a lookup table can be used to find a second by second correction value to be added to the seconds counter. -Chuck Harris Dan Rae wrote: On 12/19/2011 5:34 AM, Chuck Harris wrote: It is not clear to me that a 32KHz xtal is any less stable than a 262KHz xtal, though. I would think there would be a lot more to be gained by using a microprocessor/thermistor to measure the temperature within the watch, and provide an adjustment to compensate for the xtal's natural temperature sensitivity. Chuck, I have recently made a couple of Real Time Clocks for my homebrew radios using the Maxim DS3232 IC which has a built in TCXO at 32+ kHz doing what you describe, the temperature is checked at intervals and the corrections applied. The performance is excellent, once set, getting to what I term Harrison Level, i.e. less than a second a week error. The downside is that the standby battery demand is pretty high and my first builds using a Lithium button cell ran for only around a month max, so I had to go over to NiMH rechargeables. I suspect using this technology in a watch one would have the same problem. The best crystals for room temperature use are around 4 MHz with temperature inflections around 20C, and this is what was used in an early Braun alarm clock I had which also had this kind of performance. Long gone, alas. Dan __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://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-nutshttps://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] New precision watch
How about a turnip pocket watch with one of the new Cesium standards in it? Harrison would approve... Don mike cook Le 19/12/2011 06:47, Perry Sandeen a écrit : Is a 10 MHz or so crystal on the horizon? Dunno, but some 10-50MHz TCXO/VCTCXO are now available in 2mm packages, so why not. There might be battery longevity issues with driving the higher frequency. I guess it comes down to whether the maker can sell enough to make a profit. FWIW, My Citizen Chronomaster is has gained just 1,8 seconds in the last 12 months , well within the spec. of +/-5s. ___ 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.
Re: [time-nuts] New precision watch
But the Admiralty still wouldn't pay up ... Dave -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Don Latham Sent: 19 December 2011 19:50 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] New precision watch How about a turnip pocket watch with one of the new Cesium standards in it? Harrison would approve... Don ___ 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] New precision watch
On Tue, 20 Dec 2011 13:12:13 +1100 Jim Palfreyman jim77...@gmail.com wrote: Why don't they build a watch that measures the temperature and every time you accurately set it, it adds to a small database of time change v temperature and then adjusts itself internally. Over time it would become quite accurate I would think. Because it doesn't work that way. The temperature curve is not linear. So you would need to have a lot of reference points to get an acceptable accuracy. Ie you would need at least a dozen if not more measurements points, then calculate from that the correction factors (which isn't easy if you have no control over the temperature). It's far more economic to put the watch into a climate chamber for half a day and do one or two cycles trough the expected range. This gives you much more accurate data and the watch can then do simple lookup in a table instead of doing complicated calculations. If you do the calibration right, you can quite easily get below 1ppm (not accounting for aging). Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson ___ 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] New precision watch
Le 21/12/2011 10:53, Attila Kinali a écrit : On Tue, 20 Dec 2011 13:12:13 +1100 Jim Palfreymanjim77...@gmail.com wrote: Why don't they build a watch that measures the temperature and every time you accurately set it, it adds to a small database of time change v temperature and then adjusts itself internally. Over time it would become quite accurate I would think. For some of the techniques of compensation and timepieces using them, check out http://forums.watchuseek.com/f9/thermocompensation-methods-movements-2087.htm It's far more economic to put the watch into a climate chamber for half a day and do one or two cycles trough the expected range. This gives you much more accurate data and the watch can then do simple lookup in a table instead of doing complicated calculations. If you do the calibration right, you can quite easily get below 1ppm (not accounting for aging). Attila Kinali ___ 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] New precision watch
On Mon, 19 Dec 2011 19:12:43 -0500 Chuck Harris cfhar...@erols.com wrote: There is nothing inherent in temperature correcting a clock that should take significantly more power than would be used in a normal watch chip. Measuring the temperature would be the most power hungry operation, I would suspect... but fortunately that doesn't have to be done all that often, perhaps once per minute. Juup, it definitly should not draw much power. I own a Tissot T-Touch (first gen) that goes wrong less than 5s/y, ie it's definitly temperature compensated. Battery lifetime is several years (i actually dont know because i had to bring it back for repairs in shorter intervals than the battery holds) Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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] New precision watch
I think the Grand Seikos are specified at the same +/- 10 seconds a year accuracy as that Bulova. They use a slightly different approach though - it's a standard 32768 Hz xtal, but its thermally compensated. I don't know of any other watches that use a 262144 Hz xtal on its own, but there were some designs that used both a 32768 and 262244 Hz xtals and used the tracking between them for temperature compensation (I think this was used in some Seiko and ETA watches). The Bulova certainly has a great price for a watch of that spec. I don't know of any watches that used an oscillator as high as 10 MHz - the highest clock I ever heard of in a watch was in a very limited edition Citizen that ran at 4 MHz, and which was specced at +/- 3 seconds a year without thermal compensation. Omega also made a high-frequency watch that I think ran at 2.4 MHz and had a +/- 5 seconds / year accuracy spec. Both of these used AT-cut xtals and suffered from rather poor battery life (about 1 year). Regards, Pete On Mon, Dec 19, 2011 at 1:47 PM, Perry Sandeen sandee...@yahoo.com wrote: List, I saw an ad today for a Bulova Champlain Precisionist watch. It is supposed to be accurate to + 10 seconds a year. What stood out in the as is that they are using a 262,144 KHz crystal eight times the frequency commonly used. I don’t know if it is more accurate than the Seiko (?) discussed on the list about a year ago, but it seems to be about USD $2,100 cheaper. Around USD $600 or less depending on the model. Is a 10 MHz or so crystal on the horizon? Regards, Perrier ___ 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] New precision watch
With the CMOS logic used in watches, the big power hog is due to charging and discharging the gate capacitance of the various logic gates. The faster you charge and discharge the gate's, the more power you loose due to I2R losses, and E-M radiation. Thankfully, the high capacity lithium cells available today provide lots more uA-hours than the older silver-oxide cells of yor, so it is possible for the energy budget on a premium electronic watch to be higher than was previously acceptable. I would think that most watch manufacturers would take that extra power budget, and use it to extend the time between cell changes, and to spin more fancy dial motors. It is not clear to me that a 32KHz xtal is any less stable than a 262KHz xtal, though. I would think there would be a lot more to be gained by using a microprocessor/thermistor to measure the temperature within the watch, and provide an adjustment to compensate for the xtal's natural temperature sensitivity. -Chuck Harris Perry Sandeen wrote: List, I saw an ad today for a Bulova Champlain Precisionist watch. It is supposed to be accurate to + 10 seconds a year. What stood out in the as is that they are using a 262,144 KHz crystal eight times the frequency commonly used. I don’t know if it is more accurate than the Seiko (?) discussed on the list about a year ago, but it seems to be about USD $2,100 cheaper. Around USD $600 or less depending on the model. Is a 10 MHz or so crystal on the horizon? Regards, Perrier ___ 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] New precision watch
Le 19/12/2011 06:47, Perry Sandeen a écrit : Is a 10 MHz or so crystal on the horizon? Dunno, but some 10-50MHz TCXO/VCTCXO are now available in 2mm packages, so why not. There might be battery longevity issues with driving the higher frequency. I guess it comes down to whether the maker can sell enough to make a profit. FWIW, My Citizen Chronomaster is has gained just 1,8 seconds in the last 12 months , well within the spec. of +/-5s. ___ 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] New precision watch
On 12/19/2011 5:34 AM, Chuck Harris wrote: It is not clear to me that a 32KHz xtal is any less stable than a 262KHz xtal, though. I would think there would be a lot more to be gained by using a microprocessor/thermistor to measure the temperature within the watch, and provide an adjustment to compensate for the xtal's natural temperature sensitivity. Chuck, I have recently made a couple of Real Time Clocks for my homebrew radios using the Maxim DS3232 IC which has a built in TCXO at 32+ kHz doing what you describe, the temperature is checked at intervals and the corrections applied. The performance is excellent, once set, getting to what I term Harrison Level, i.e. less than a second a week error. The downside is that the standby battery demand is pretty high and my first builds using a Lithium button cell ran for only around a month max, so I had to go over to NiMH rechargeables. I suspect using this technology in a watch one would have the same problem. The best crystals for room temperature use are around 4 MHz with temperature inflections around 20C, and this is what was used in an early Braun alarm clock I had which also had this kind of performance. Long gone, alas. Dan ___ 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] New precision watch
dan...@verizon.net wrote: The best crystals for room temperature use are around 4 MHz with temperature inflections around 20C, and this is what was used in an early Braun alarm clock I had which also had this kind of performance. Long gone, alas. and this is what the clock of my old german car does (4 MHz crystal). Its performance always surprised me. Antonio I8IOV ___ 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] New precision watch
Looking at the datasheet for the DS3232, it doesn't appear that they mean for it to run off of a small coin cell in a watch. Its battery operating capability is purely to keep it running when the main power is turned off. I would suspect that the DS3232's power consumption is due to its being able to drive sizable loads on its various pins. There is nothing inherent in temperature correcting a clock that should take significantly more power than would be used in a normal watch chip. Measuring the temperature would be the most power hungry operation, I would suspect... but fortunately that doesn't have to be done all that often, perhaps once per minute. After the temperature is measured, a lookup table can be used to find a second by second correction value to be added to the seconds counter. -Chuck Harris Dan Rae wrote: On 12/19/2011 5:34 AM, Chuck Harris wrote: It is not clear to me that a 32KHz xtal is any less stable than a 262KHz xtal, though. I would think there would be a lot more to be gained by using a microprocessor/thermistor to measure the temperature within the watch, and provide an adjustment to compensate for the xtal's natural temperature sensitivity. Chuck, I have recently made a couple of Real Time Clocks for my homebrew radios using the Maxim DS3232 IC which has a built in TCXO at 32+ kHz doing what you describe, the temperature is checked at intervals and the corrections applied. The performance is excellent, once set, getting to what I term Harrison Level, i.e. less than a second a week error. The downside is that the standby battery demand is pretty high and my first builds using a Lithium button cell ran for only around a month max, so I had to go over to NiMH rechargeables. I suspect using this technology in a watch one would have the same problem. The best crystals for room temperature use are around 4 MHz with temperature inflections around 20C, and this is what was used in an early Braun alarm clock I had which also had this kind of performance. Long gone, alas. Dan ___ 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.
