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] Efratom FRK - no 10Mhz oscillator
Yeah, that was why I suggested just sticking a random 10MHz xtal across the pins on the board (with the existing xtal wiring disconnected) - if the rest of the circuit is good, then the oscillator should start up with no problems - if it doesn't, then suspect a fault somewhere else. I just pulled out the manual, and I would start by lifting the connection on E7, and connecting a 10MHz xtal in series with a 10pF cap between the E7 pin and ground. This will bypass both the xtal and the frequency adjustment circuit. If that doesn't work, then the oscillator circuit is the problem - if it does work, then remove the 10 pF cap and connect the xtal directly between E7 and E8 - if it still works, it's almost certainly a bad xtal. If it worked with the 10 pF cap but not with the E8 connection, then check the control voltage (E9: 0.5V-17V) - if that looks good, then suspect the frequency control circuit. If it's bad, then try hooking it to +5V to verify the oscillator and then troubleshoot the servo board. Regards, Pete On Wed, Dec 21, 2011 at 5:00 AM, Azelio Boriani azelio.bori...@screen.it wrote: 10MHz crystals used in OCXO are designed for the temperature of the oven so it is not possible to find an off-the-shelf suitable crystal. Better find a crystal coming from an OCXO. On Tue, Dec 20, 2011 at 7:10 PM, Peter Bell bell.pe...@gmail.com wrote: Hi, Don It's been quite a while since I worked on a FRK, but from what I remember the only signals going to that oscillator board are power and the control voltage. It might be worth checking the control voltage to see if it's at a plausible value (nominal is 5V, spec range is 1V-16V, IIRC) - if you have a spare xtal around, just try connecting it to the pins on the PCB and see if it starts up. I'm not aware of the xtals being failure prone - I have seen one FRK with a bad one, but having seen the condition of the system it was removed from, that was clearly impact damage. Regards, Pete On Wed, Dec 21, 2011 at 1:29 AM, Don Lewis dlewis6...@austin.rr.com wrote: A little help, pls, from the more experienced. This is my first time into one of these .I have listened and learned from you' all for some time, though. It can be intimidating in this close-packed FRK. I am trying to bring up an Efratom FRK I have had for a while. The 10 MHz oscillator does not start upon power on. Any ideas where to look? I have done the following: * I have it opened-up and applied 24vDC and the current starts up initially at 1.45 amp and slowly goes down to ~.6- .8 amps. * Since I have no 10 MHz output, .so I looked at the oscillator board and nothing out from it. * The 17 volt dc supply-rail is good, and the VCO input signal to the varacter control-circuitry is constantly ramping up and down slowly between ~1volt and ~15 volts. * All the transistors in the oscillator circuit seem ok with a VOM, ..and when I purposely inject a 10Mhz signal into the collector of the 'oscillator' transistor (Q3), .I do get a clean 10Mhz out of the unit (of course it won't lock), .and I haven't even been into the rest of the unit. * I think the crystal is bad, .I took the cover off the crystal oven, it 'looks' ok, . and the crystal heater in the oven is heating and regulating. Any ideas? .does the 10 MHz crystal in these have a history of failing? Can I get a replacement crystal for it easily? How can I test this crystal for pass/fail? Thanks, .just my first test of the waters as a fledging time-nut. Don Lewis Austin, TX ___ 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.
Re: [time-nuts] Efratom FRK - no 10Mhz oscillator
Thanks, Pete. Good tips. I ordered 10 crystals this morning, ...they are dirt cheap. Will try and test one as you suggested. If it is the 'crystal', a bad crystal, ...what then? Do I try to place one of these cheap ones in the oven, ...or do I try to just run it outside the oven or find a high-temperature crystal??? The crystal oven/controller seems fine, ...hot enough to hurt my fingers. Thanks, ...-Don -- -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Peter Bell Sent: Wednesday, December 21, 2011 5:28 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Efratom FRK - no 10Mhz oscillator Yeah, that was why I suggested just sticking a random 10MHz xtal across the pins on the board (with the existing xtal wiring disconnected) - if the rest of the circuit is good, then the oscillator should start up with no problems - if it doesn't, then suspect a fault somewhere else. I just pulled out the manual, and I would start by lifting the connection on E7, and connecting a 10MHz xtal in series with a 10pF cap between the E7 pin and ground. This will bypass both the xtal and the frequency adjustment circuit. If that doesn't work, then the oscillator circuit is the problem - if it does work, then remove the 10 pF cap and connect the xtal directly between E7 and E8 - if it still works, it's almost certainly a bad xtal. If it worked with the 10 pF cap but not with the E8 connection, then check the control voltage (E9: 0.5V-17V) - if that looks good, then suspect the frequency control circuit. If it's bad, then try hooking it to +5V to verify the oscillator and then troubleshoot the servo board. Regards, Pete On Wed, Dec 21, 2011 at 5:00 AM, Azelio Boriani azelio.bori...@screen.it wrote: 10MHz crystals used in OCXO are designed for the temperature of the oven so it is not possible to find an off-the-shelf suitable crystal. Better find a crystal coming from an OCXO. On Tue, Dec 20, 2011 at 7:10 PM, Peter Bell bell.pe...@gmail.com wrote: Hi, Don It's been quite a while since I worked on a FRK, but from what I remember the only signals going to that oscillator board are power and the control voltage. It might be worth checking the control voltage to see if it's at a plausible value (nominal is 5V, spec range is 1V-16V, IIRC) - if you have a spare xtal around, just try connecting it to the pins on the PCB and see if it starts up. I'm not aware of the xtals being failure prone - I have seen one FRK with a bad one, but having seen the condition of the system it was removed from, that was clearly impact damage. Regards, Pete On Wed, Dec 21, 2011 at 1:29 AM, Don Lewis dlewis6...@austin.rr.com wrote: A little help, pls, from the more experienced. This is my first time into one of these .I have listened and learned from you' all for some time, though. It can be intimidating in this close-packed FRK. I am trying to bring up an Efratom FRK I have had for a while. The 10 MHz oscillator does not start upon power on. Any ideas where to look? I have done the following: * I have it opened-up and applied 24vDC and the current starts up initially at 1.45 amp and slowly goes down to ~.6- .8 amps. * Since I have no 10 MHz output, .so I looked at the oscillator board and nothing out from it. * The 17 volt dc supply-rail is good, and the VCO input signal to the varacter control-circuitry is constantly ramping up and down slowly between ~1volt and ~15 volts. * All the transistors in the oscillator circuit seem ok with a VOM, ..and when I purposely inject a 10Mhz signal into the collector of the 'oscillator' transistor (Q3), .I do get a clean 10Mhz out of the unit (of course it won't lock), .and I haven't even been into the rest of the unit. * I think the crystal is bad, .I took the cover off the crystal oven, it 'looks' ok, . and the crystal heater in the oven is heating and regulating. Any ideas? .does the 10 MHz crystal in these have a history of failing? Can I get a replacement crystal for it easily? How can I test this crystal for pass/fail? Thanks, .just my first test of the waters as a fledging time-nut. Don Lewis Austin, TX ___ 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
Re: [time-nuts] Efratom FRK - no 10Mhz oscillator
Hi, Don If the xtal is bad, you will really have to try and find one that's designed to work at whatever temperature the oven is set to (65c, I think..) - trying to put a regular xtal in there that was designed for room temperature operation will likely not work since it will run 8-10 ppm high and have a very poor tempco. I'm not sure what the load capacitance of the original xtal was, but you could guesstimate it based on the load capacitance of your test xtal and seeing how close to the right frequency you get. Regards, Pete On Wed, Dec 21, 2011 at 10:04 PM, Don Lewis dlewis6...@austin.rr.com wrote: Thanks, Pete. Good tips. I ordered 10 crystals this morning, ...they are dirt cheap. Will try and test one as you suggested. If it is the 'crystal', a bad crystal, ...what then? Do I try to place one of these cheap ones in the oven, ...or do I try to just run it outside the oven or find a high-temperature crystal??? The crystal oven/controller seems fine, ...hot enough to hurt my fingers. Thanks, ...-Don -- -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Peter Bell Sent: Wednesday, December 21, 2011 5:28 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Efratom FRK - no 10Mhz oscillator Yeah, that was why I suggested just sticking a random 10MHz xtal across the pins on the board (with the existing xtal wiring disconnected) - if the rest of the circuit is good, then the oscillator should start up with no problems - if it doesn't, then suspect a fault somewhere else. I just pulled out the manual, and I would start by lifting the connection on E7, and connecting a 10MHz xtal in series with a 10pF cap between the E7 pin and ground. This will bypass both the xtal and the frequency adjustment circuit. If that doesn't work, then the oscillator circuit is the problem - if it does work, then remove the 10 pF cap and connect the xtal directly between E7 and E8 - if it still works, it's almost certainly a bad xtal. If it worked with the 10 pF cap but not with the E8 connection, then check the control voltage (E9: 0.5V-17V) - if that looks good, then suspect the frequency control circuit. If it's bad, then try hooking it to +5V to verify the oscillator and then troubleshoot the servo board. Regards, Pete On Wed, Dec 21, 2011 at 5:00 AM, Azelio Boriani azelio.bori...@screen.it wrote: 10MHz crystals used in OCXO are designed for the temperature of the oven so it is not possible to find an off-the-shelf suitable crystal. Better find a crystal coming from an OCXO. On Tue, Dec 20, 2011 at 7:10 PM, Peter Bell bell.pe...@gmail.com wrote: Hi, Don It's been quite a while since I worked on a FRK, but from what I remember the only signals going to that oscillator board are power and the control voltage. It might be worth checking the control voltage to see if it's at a plausible value (nominal is 5V, spec range is 1V-16V, IIRC) - if you have a spare xtal around, just try connecting it to the pins on the PCB and see if it starts up. I'm not aware of the xtals being failure prone - I have seen one FRK with a bad one, but having seen the condition of the system it was removed from, that was clearly impact damage. Regards, Pete On Wed, Dec 21, 2011 at 1:29 AM, Don Lewis dlewis6...@austin.rr.com wrote: A little help, pls, from the more experienced. This is my first time into one of these .I have listened and learned from you' all for some time, though. It can be intimidating in this close-packed FRK. I am trying to bring up an Efratom FRK I have had for a while. The 10 MHz oscillator does not start upon power on. Any ideas where to look? I have done the following: * I have it opened-up and applied 24vDC and the current starts up initially at 1.45 amp and slowly goes down to ~.6- .8 amps. * Since I have no 10 MHz output, .so I looked at the oscillator board and nothing out from it. * The 17 volt dc supply-rail is good, and the VCO input signal to the varacter control-circuitry is constantly ramping up and down slowly between ~1volt and ~15 volts. * All the transistors in the oscillator circuit seem ok with a VOM, ..and when I purposely inject a 10Mhz signal into the collector of the 'oscillator' transistor (Q3), .I do get a clean 10Mhz out of the unit (of course it won't lock), .and I haven't even been into the rest of the unit. * I think the crystal is bad, .I took the cover off the crystal oven, it 'looks' ok, . and the crystal heater in the oven is heating and regulating. Any ideas? .does the 10 MHz crystal in these have a history of failing? Can I get a replacement crystal for it easily? How can I test this crystal for pass/fail? Thanks, .just my first test of the
Re: [time-nuts] Efratom FRK - no 10Mhz oscillator
Hi Don, I'm assuming that you've checked for obvious things like bad solder joints. After 20 or more years in that heat, anything is possible. Luckily, the oscillator board doesn't have too many connections to remove when you pull the board. I use a 20X magnifier to really get close. I've often found problems that you can't see with less magnification. In one message you mentioned that touching the crystal oven with an external 10 MHz signal starts the oscillator. Isn't the oven supposed to be grounded? I agree with other posters that if you have a bad crystal, you'll have to find a replacement that's made to be used in an oven. However, any old 10 MHz crystal will be useful to diagnose the problem. It might be possible to sacrifice another OCXO and transplant the crystal into the FRK. Your best bet would be an OCXO with an AT crystal. I wouldn't try using an SC crystal. The circuitry would be significantly different. The oven would have to be retuned to match the new crystal, but that's just a resistor change. If you're up for a bigger challenge, you could try interfacing an external OCXO to the Rubidium loop. Rubidiums are typically marketed for low drift applications rather than low Allan Deviation or phase noise. I've wondered whether a high quality SC-crystal OCXO would make a significant improvement in a Rubidium's short-term performance. I've never had a Rubidium with a dead oscillator to experiment on. Ed On 12/21/2011 8:04 AM, Don Lewis wrote: Thanks, Pete. Good tips. I ordered 10 crystals this morning, ...they are dirt cheap. Will try and test one as you suggested. If it is the 'crystal', a bad crystal, ...what then? Do I try to place one of these cheap ones in the oven, ...or do I try to just run it outside the oven or find a high-temperature crystal??? The crystal oven/controller seems fine, ...hot enough to hurt my fingers. Thanks, ...-Don -- -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Peter Bell Sent: Wednesday, December 21, 2011 5:28 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Efratom FRK - no 10Mhz oscillator Yeah, that was why I suggested just sticking a random 10MHz xtal across the pins on the board (with the existing xtal wiring disconnected) - if the rest of the circuit is good, then the oscillator should start up with no problems - if it doesn't, then suspect a fault somewhere else. I just pulled out the manual, and I would start by lifting the connection on E7, and connecting a 10MHz xtal in series with a 10pF cap between the E7 pin and ground. This will bypass both the xtal and the frequency adjustment circuit. If that doesn't work, then the oscillator circuit is the problem - if it does work, then remove the 10 pF cap and connect the xtal directly between E7 and E8 - if it still works, it's almost certainly a bad xtal. If it worked with the 10 pF cap but not with the E8 connection, then check the control voltage (E9: 0.5V-17V) - if that looks good, then suspect the frequency control circuit. If it's bad, then try hooking it to +5V to verify the oscillator and then troubleshoot the servo board. Regards, Pete On Wed, Dec 21, 2011 at 5:00 AM, Azelio Boriani azelio.bori...@screen.it wrote: 10MHz crystals used in OCXO are designed for the temperature of the oven so it is not possible to find an off-the-shelf suitable crystal. Better find a crystal coming from an OCXO. On Tue, Dec 20, 2011 at 7:10 PM, Peter Bellbell.pe...@gmail.com wrote: Hi, Don It's been quite a while since I worked on a FRK, but from what I remember the only signals going to that oscillator board are power and the control voltage. It might be worth checking the control voltage to see if it's at a plausible value (nominal is 5V, spec range is 1V-16V, IIRC) - if you have a spare xtal around, just try connecting it to the pins on the PCB and see if it starts up. I'm not aware of the xtals being failure prone - I have seen one FRK with a bad one, but having seen the condition of the system it was removed from, that was clearly impact damage. Regards, Pete On Wed, Dec 21, 2011 at 1:29 AM, Don Lewisdlewis6...@austin.rr.com wrote: A little help, pls, from the more experienced. This is my first time into one of these .I have listened and learned from you' all for some time, though. It can be intimidating in this close-packed FRK. I am trying to bring up an Efratom FRK I have had for a while. The 10 MHz oscillator does not start upon power on. Any ideas where to look? I have done the following: * I have it opened-up and applied 24vDC and the current starts up initially at 1.45 amp and slowly goes down to ~.6- .8 amps. * Since I have no 10 MHz output, .so I looked at the oscillator board and nothing out from it. * The 17 volt dc supply-rail is good, and the VCO input
[time-nuts] FE-5680A temp coefficient seems to be -7E-12 per degree C
My measurements on one FE-5680A Rb sample indicate a temperature coefficient of -7E-12 per degree C (T measured at exterior case top center); more details below. Can anyone opine if this is a reasonable value? I can't say anything about long-term drift until I stabilize the case temperature. Currently experimenting with a variable-speed fan and PID controller looking at a thermistor attached to the case, to that end. The starting point of -3.2E-10 offset is just how the unit arrived, I have not yet tried changing the frequency via RS-232 commands. With a 40mm 12V fan running at 5V and pointed at a 4x6x1 finned heatsink the unit is mounted on, the case temp. drops 10 degrees (55C - 45C), and the unit 15Vdc power draw increases 2 watts. (Perhaps a bit less, I actually measured the power at 120Vac with a WattsUp Pro meter, but I assume my DVE 15V 2A switcher is pretty efficient. Supply is from lightobject.com and actually provides 14.84 V, but that seems to work.) Ambient room temp was also logged; it varies by about 2 C as building heater cycles. FE-5680A 10 MHz F_offset vs. GPS using picPET: http://www.leapsecond.com/pic/picpet.htm and Sure Electronics GPS: http://www.leapsecond.com/pages/MG1613S/ -- Foff = -3.20E-10 7:30 am Dec.14 2011 (32 hours). Case top: ~45 C Foff = -3.22E-10 9 pm Dec. 15 2011 (14.5 hours). Case top: 41.5-44.5 C Foff = -3.227E-10 3 pm Dec. 17 (40.9 hours). Case top: 42-44 C Foff = -3.216E-10 11 pm Dec. 19 (46.5 hours). Case top: 42-44 C Foff = -3.902E-10 10 am Dec 20 (11 hours). Case top: 52.5-53.5 C (fan off) Foff = -3.910E-10 10 am Dec. 21 (12 hours of data). Case top: 52.5-53.5 C conclusion: tempco is -7E-11 with +10 C, or about -7E-12 per degree C -- see also: https://picasaweb.google.com/109928236040342205185/FE5680A -- ___ 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.
[time-nuts] FE-5680A at WA7KGX
I removed the oscillator from the circuit board using an Allen wrench on the other side of the board. Somewhat easier than unscrewing the obvious way, especially with a worn tool. I removed the lid and lifted the plastic sheet. I did not see anything alarming. It is now mounted on the outside of the chassis that holds my Thunderbolt and its switching power supply. An AC adapter from an old Toshiba laptop provides the 15 volts. 5 volts is shared with the Thunderbolt, which draws very little from 5 volts. A big fat line filter keeps the RFI inside. I have powered up the 5680A several times. The first time took about 30 minutes to lock. Subsequent times took the usual several minutes to lock. As I write this the 5680 has stayed within about 50 degrees of phase lock with the Thunderbolt's 10 MHz output for 316 minutes and counting. Not bad for $40.00. Still no idea why the 5 volt draw is 340 ma instead of 90 ma. The 15 volt draw is normal. -- Chuck Forsberg WA7KGX N2469R c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc The High Reliability Software 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 ___ 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] Efratom FRK - no 10Mhz oscillator
Thanks, Ed, all good ideas. Thanks for the tips. Today, I unhooked the 10 MHz crystal from the oscillator circuit and tried to drive the crystal at low-power with my signal generator and look for resonance my scope. There was no resonant-peak at 10 MHz ...so either the crystal is bad or perhaps not connected inside the oven. I took the cover off the little crystal oven, ...it is really clean inside, ...there is the gold-plated crystal and then a lot of grey RTV around the crystal socket and covering the temp-sensor. I think I will try to dig out all that RTV and see if hopefully a wire to the crystal is broken. The crystal oven is not connected to ground (or at least it is currently not grounded.) -Don -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf of Ed Palmer Sent: Wednesday, December 21, 2011 12:12 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Efratom FRK - no 10 MHz oscillator Hi Don, I'm assuming that you've checked for obvious things like bad solder joints. After 20 or more years in that heat, anything is possible. Luckily, the oscillator board doesn't have too many connections to remove when you pull the board. I use a 20X magnifier to really get close. I've often found problems that you can't see with less magnification. In one message you mentioned that touching the crystal oven with an external 10 MHz signal starts the oscillator. Isn't the oven supposed to be grounded? I agree with other posters that if you have a bad crystal, you'll have to find a replacement that's made to be used in an oven. However, any old 10 MHz crystal will be useful to diagnose the problem. It might be possible to sacrifice another OCXO and transplant the crystal into the FRK. Your best bet would be an OCXO with an AT crystal. I wouldn't try using an SC crystal. The circuitry would be significantly different. The oven would have to be retuned to match the new crystal, but that's just a resistor change. If you're up for a bigger challenge, you could try interfacing an external OCXO to the Rubidium loop. Rubidiums are typically marketed for low drift applications rather than low Allan Deviation or phase noise. I've wondered whether a high quality SC-crystal OCXO would make a significant improvement in a Rubidium's short-term performance. I've never had a Rubidium with a dead oscillator to experiment on. Ed On 12/21/2011 8:04 AM, Don Lewis wrote: Thanks, Pete. Good tips. I ordered 10 crystals this morning, ...they are dirt cheap. Will try and test one as you suggested. If it is the 'crystal', a bad crystal, ...what then? Do I try to place one of these cheap ones in the oven, ...or do I try to just run it outside the oven or find a high-temperature crystal??? The crystal oven/controller seems fine, ...hot enough to hurt my fingers. Thanks, ...-Don -- -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Peter Bell Sent: Wednesday, December 21, 2011 5:28 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Efratom FRK - no 10Mhz oscillator Yeah, that was why I suggested just sticking a random 10MHz xtal across the pins on the board (with the existing xtal wiring disconnected) - if the rest of the circuit is good, then the oscillator should start up with no problems - if it doesn't, then suspect a fault somewhere else. I just pulled out the manual, and I would start by lifting the connection on E7, and connecting a 10MHz xtal in series with a 10pF cap between the E7 pin and ground. This will bypass both the xtal and the frequency adjustment circuit. If that doesn't work, then the oscillator circuit is the problem - if it does work, then remove the 10 pF cap and connect the xtal directly between E7 and E8 - if it still works, it's almost certainly a bad xtal. If it worked with the 10 pF cap but not with the E8 connection, then check the control voltage (E9: 0.5V-17V) - if that looks good, then suspect the frequency control circuit. If it's bad, then try hooking it to +5V to verify the oscillator and then troubleshoot the servo board. Regards, Pete On Wed, Dec 21, 2011 at 5:00 AM, Azelio Boriani azelio.bori...@screen.it wrote: 10MHz crystals used in OCXO are designed for the temperature of the oven so it is not possible to find an off-the-shelf suitable crystal. Better find a crystal coming from an OCXO. On Tue, Dec 20, 2011 at 7:10 PM, Peter Bellbell.pe...@gmail.com wrote: Hi, Don It's been quite a while since I worked on a FRK, but from what I remember the only signals going to that oscillator board are power and the control voltage. It might be worth checking the control voltage to see if it's at a plausible value (nominal is 5V, spec range is 1V-16V, IIRC) - if you have a
Re: [time-nuts] FE-5680A at WA7KGX
Hi, Chuck From my investigations of the circuits, the only places the 5V goes is the 74ACT240 next to the D-type connector and the Maxim 3.3V regulator - he first thing I would check is to apply just the 5V to the unit and see if the 'ACT240 gets hot - to really confirm it, just lift pin 20 of this chip and see if the current drops. Regards, Pete On Thu, Dec 22, 2011 at 5:27 AM, Chuck Forsberg WA7KGX N2469R c...@omen.com wrote: I removed the oscillator from the circuit board using an Allen wrench on the other side of the board. Somewhat easier than unscrewing the obvious way, especially with a worn tool. I removed the lid and lifted the plastic sheet. I did not see anything alarming. It is now mounted on the outside of the chassis that holds my Thunderbolt and its switching power supply. An AC adapter from an old Toshiba laptop provides the 15 volts. 5 volts is shared with the Thunderbolt, which draws very little from 5 volts. A big fat line filter keeps the RFI inside. I have powered up the 5680A several times. The first time took about 30 minutes to lock. Subsequent times took the usual several minutes to lock. As I write this the 5680 has stayed within about 50 degrees of phase lock with the Thunderbolt's 10 MHz output for 316 minutes and counting. Not bad for $40.00. Still no idea why the 5 volt draw is 340 ma instead of 90 ma. The 15 volt draw is normal. -- Chuck Forsberg WA7KGX N2469R c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc The High Reliability Software 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 ___ 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.
