Re: [time-nuts] Aging rate of crystals
"doomday machine" just refers to the ultimate performance design. Len was a perfectionist. Rick Rex wrote: > Rick Karlquist wrote: >> I wish Len Cutler were >> still around to tell about it. He proudly keep a 107 prototype >> in his office. Len couldn't bring himself to design anything that wasn't >> a doomsday machine. >> >> Rick Karlquist, N6RK >> >> > Rick, you lost me with the last sentence. What do you mean? > > ___ 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] Aging rate of crystals
> That's incredible Mike. I've never seen a 10811 or E1938 within a > factor of 10 of the first number you gave, let alone the second. > The second rate would be very respectible for a Rb standard. > I believe those antique oscillators you have are using non-HP > made xtals at 1 MHz (or 5 MHz at the most) in glass packages. > While a steady temperature and solid mounting is great, it takes > more than that to put up these kind of numbers. Congratulations, keep > taking good care of those old war horses. I wish Len Cutler were > still around to tell about it. He proudly keep a 107 prototype > in his office. Len couldn't bring himself to design anything that wasn't > a doomsday machine. > > Rick Karlquist, N6RK Rick, I have an old HP 106 with similar amazingly low drift performance and was able to talk to Len about it a few years ago. He was very pleased to hear it was still working, and so well. It drifted a just few parts in 10^11th over a 40 day run, which puts the daily drift rate in the mid to low -13's. At this point the system tempco (106 or Rb) is clearly a greater factor than the resonator drift rate (and my lab was in the garage ten years ago). Some old plots are here: http://www.leapsecond.com/museum/hp106b/ The 106 used a monster-sized 2.5 Mc AT-cut xtal, similar to the original Sulzer's of that era. /tvb ___ 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] Aging rate of crystals
Rick Karlquist wrote: > I wish Len Cutler were > still around to tell about it. He proudly keep a 107 prototype > in his office. Len couldn't bring himself to design anything that wasn't > a doomsday machine. > > Rick Karlquist, N6RK > > Rick, you lost me with the last sentence. What do you mean? ___ 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] Aging rate of crystals
I'm not familiar with the E1938, but the 10811, I believe is one of the small "hi stab" units that HP put into their higher end counters. It uses a single oven where the 103 and 107 used double ovens. Incidentally, the 103 uses a 1 MHz rock and the 107 uses a 5 MHz rock. -Mike- At 03:27 PM 2/19/2008, you wrote: >Mike Fahmie wrote: > > Somewhere, I have a NASA pub that describes a technique using Gamma Rays > > to > > accelerate aging so that later aging is much reduced, can't seem to find > > it > > now. I would guess that the radiation cause the stresses to relax. NASA > > was > > evidently interested because satellites experience a lot more radiation > > than we receive here on the surface and it probably caused a rapid > > frequency shift in otherwise unradiated crystals. > >I remember some of the crystal gurus talking about this. >I suspect it didn't pan out or everyone would be doing it. >I also remember them saying that radiation causes "color centers" >to appear. > > > I have two HP quartz oscillators that I've been running and logging for > > well over a decade. They run 24/7 and are on battery backup. The HP-103 > > shows about 6 parts in 10^-12/day and the HP-107 about 2 parts in > > 10^-13/day. I attribute this to steady temperature and solid mounting in a > > heavy rack. > > > > -Mike- > >That's incredible Mike. I've never seen a 10811 or E1938 within a >factor of 10 of the first number you gave, let alone the second. >The second rate would be very respectible for a Rb standard. >I believe those antique oscillators you have are using non-HP >made xtals at 1 MHz (or 5 MHz at the most) in glass packages. >While a steady temperature and solid mounting is great, it takes >more than that to put up these kind of numbers. Congratulations, keep >taking good care of those old war horses. I wish Len Cutler were >still around to tell about it. He proudly keep a 107 prototype >in his office. Len couldn't bring himself to design anything that wasn't >a doomsday machine. > >Rick Karlquist, N6RK > > >___ >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] Aging rate of crystals
Mike Fahmie wrote: > Somewhere, I have a NASA pub that describes a technique using Gamma Rays > to > accelerate aging so that later aging is much reduced, can't seem to find > it > now. I would guess that the radiation cause the stresses to relax. NASA > was > evidently interested because satellites experience a lot more radiation > than we receive here on the surface and it probably caused a rapid > frequency shift in otherwise unradiated crystals. I remember some of the crystal gurus talking about this. I suspect it didn't pan out or everyone would be doing it. I also remember them saying that radiation causes "color centers" to appear. > I have two HP quartz oscillators that I've been running and logging for > well over a decade. They run 24/7 and are on battery backup. The HP-103 > shows about 6 parts in 10^-12/day and the HP-107 about 2 parts in > 10^-13/day. I attribute this to steady temperature and solid mounting in a > heavy rack. > > -Mike- That's incredible Mike. I've never seen a 10811 or E1938 within a factor of 10 of the first number you gave, let alone the second. The second rate would be very respectible for a Rb standard. I believe those antique oscillators you have are using non-HP made xtals at 1 MHz (or 5 MHz at the most) in glass packages. While a steady temperature and solid mounting is great, it takes more than that to put up these kind of numbers. Congratulations, keep taking good care of those old war horses. I wish Len Cutler were still around to tell about it. He proudly keep a 107 prototype in his office. Len couldn't bring himself to design anything that wasn't a doomsday machine. Rick Karlquist, N6RK ___ 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] Aging rate of crystals
Aging is a composite of phenomena sometimes resulting in a negative rate and sometimes in a positive rate (most common). Some causes that haven't been mentioned in this thread are the slow release of stress in the crystalline structure created by shock or temperature excursion, and the diffusion of contact metalization into the crystal. A transistors gain can change with time and temperature, thus changing the phase shift and forcing the oscillating frequency to move up or down the phase plot of the crystal to compensate. Other changes in passive components can cause the same effect. I suppose one might also expect that atoms may be slowly shed from the bulk over time and (probably) increase the frequency. Somewhere, I have a NASA pub that describes a technique using Gamma Rays to accelerate aging so that later aging is much reduced, can't seem to find it now. I would guess that the radiation cause the stresses to relax. NASA was evidently interested because satellites experience a lot more radiation than we receive here on the surface and it probably caused a rapid frequency shift in otherwise unradiated crystals. I have two HP quartz oscillators that I've been running and logging for well over a decade. They run 24/7 and are on battery backup. The HP-103 shows about 6 parts in 10^-12/day and the HP-107 about 2 parts in 10^-13/day. I attribute this to steady temperature and solid mounting in a heavy rack. -Mike- At 03:41 PM 2/18/2008, you wrote: >The long term aging rate is due entirely to the crystal, >for all practical purposes, for any well designed oscillator >circuit (or even a mediocre design). The aging of the >crystal is basically not predictable. It's like the famous saying >by J P Morgan when asked what the stock market will do: >"It will fluctuate." About the best you can do is test >the aging for a few months and hope it won't get worse >in the future. You have to be careful about getting >an oscillator that simply got lucky during your aging >test and put in much better than typical numbers. This >can happen if the direction of aging changes (not unusual) >in the middle of the aging test. You >shouldn't overpromise aging compared to what you know >your process can support. Other than holding the temperature >constant, there is nothing else you need to do to get >the best aging the crystal can do. If you get a lucky >oscillator that has really good aging, it might continue >to be really good, but there is no guarantee. > >Cheap crystals might have more predictable aging due to >outgassing processes. However, this will be a large >amount of aging. As you eliminate known causes of aging, >it gets less predictable. > >Rick Karlquist N6RK > >[EMAIL PROTECTED] wrote: > > I learn from this discussion that the aging rate claimed by > manufacturers would refer to the > > aging of the whole assembly, not the crystal alone. And for practical > purposes that is correct. > > And even in the case of sealed assemblies, components other than the > crystal itself may affect > > the overall measured drift. > > So my original question on this subject seems to lose any sense, > because we will never be able > > to measure the aging of the crystal alone (if any, at this point) and > hence variations in the > > aging rate either. > > Anyway some doubts of mine are not yet fully answered by this > discussion, and I would appreciate > > your opinions. > > Given a good quality sealed OCXO running in constant ambient > temperature, what kind of aging > > curve should one expect, a fluctuating one? (I understand that this > might be the case, due > > to the interaction of known "intrinsic" aging factors having different > timescales, as I've just > > learnt on this list. A "regular" curve would be hard to get). > > May it happen that fluctuations in frequency due to "external" causes > such as tides, geomagnetic > > storms, or so, and not actually affecting the "aging rate", are > interpreted as fluctuations > > in the aging rate? > > > > I'm running a simple test comparing an OCXO (option 04E on a military > Racal 1992 counter) to > > rubidium (LPRO), the counter being counting the LPRO. The test is > running since about two weeks, > > and I started recording three days after power up. In the first days > the OCXO showed a decreasing > > drift starting with some 3x10e-10 per day until it reached a stability > within +/- 1x10e-10 in the > > last 5 days (that is, since 5 days back, the counters reads always the > same value +/- the occasional > > uncertainty of the rightmost (11th) digit (10 seconds gate time). The > OCXO specs are <= 5x10e-10 > > per day. I didn't notice whether it is sealed, and won't check right > now. I don't expect that the > > counter will always stay there, and I don't know what to think when the > drift (aging rate?) will > > change. > > > > Thanks, > > Antonio I8IOV > > > > > > > > ___ > > time-nuts
Re: [time-nuts] Aging rate of crystals
The long term aging rate is due entirely to the crystal, for all practical purposes, for any well designed oscillator circuit (or even a mediocre design). The aging of the crystal is basically not predictable. It's like the famous saying by J P Morgan when asked what the stock market will do: "It will fluctuate." About the best you can do is test the aging for a few months and hope it won't get worse in the future. You have to be careful about getting an oscillator that simply got lucky during your aging test and put in much better than typical numbers. This can happen if the direction of aging changes (not unusual) in the middle of the aging test. You shouldn't overpromise aging compared to what you know your process can support. Other than holding the temperature constant, there is nothing else you need to do to get the best aging the crystal can do. If you get a lucky oscillator that has really good aging, it might continue to be really good, but there is no guarantee. Cheap crystals might have more predictable aging due to outgassing processes. However, this will be a large amount of aging. As you eliminate known causes of aging, it gets less predictable. Rick Karlquist N6RK [EMAIL PROTECTED] wrote: > I learn from this discussion that the aging rate claimed by manufacturers > would refer to the > aging of the whole assembly, not the crystal alone. And for practical > purposes that is correct. > And even in the case of sealed assemblies, components other than the crystal > itself may affect > the overall measured drift. > So my original question on this subject seems to lose any sense, because we > will never be able > to measure the aging of the crystal alone (if any, at this point) and hence > variations in the > aging rate either. > Anyway some doubts of mine are not yet fully answered by this discussion, and > I would appreciate > your opinions. > Given a good quality sealed OCXO running in constant ambient temperature, > what kind of aging > curve should one expect, a fluctuating one? (I understand that this might be > the case, due > to the interaction of known "intrinsic" aging factors having different > timescales, as I've just > learnt on this list. A "regular" curve would be hard to get). > May it happen that fluctuations in frequency due to "external" causes such as > tides, geomagnetic > storms, or so, and not actually affecting the "aging rate", are interpreted > as fluctuations > in the aging rate? > > I'm running a simple test comparing an OCXO (option 04E on a military Racal > 1992 counter) to > rubidium (LPRO), the counter being counting the LPRO. The test is running > since about two weeks, > and I started recording three days after power up. In the first days the OCXO > showed a decreasing > drift starting with some 3x10e-10 per day until it reached a stability within > +/- 1x10e-10 in the > last 5 days (that is, since 5 days back, the counters reads always the same > value +/- the occasional > uncertainty of the rightmost (11th) digit (10 seconds gate time). The OCXO > specs are <= 5x10e-10 > per day. I didn't notice whether it is sealed, and won't check right now. I > don't expect that the > counter will always stay there, and I don't know what to think when the drift > (aging rate?) will > change. > > Thanks, > 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. > > ___ 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] Aging rate of crystals
I learn from this discussion that the aging rate claimed by manufacturers would refer to the aging of the whole assembly, not the crystal alone. And for practical purposes that is correct. And even in the case of sealed assemblies, components other than the crystal itself may affect the overall measured drift. So my original question on this subject seems to lose any sense, because we will never be able to measure the aging of the crystal alone (if any, at this point) and hence variations in the aging rate either. Anyway some doubts of mine are not yet fully answered by this discussion, and I would appreciate your opinions. Given a good quality sealed OCXO running in constant ambient temperature, what kind of aging curve should one expect, a fluctuating one? (I understand that this might be the case, due to the interaction of known "intrinsic" aging factors having different timescales, as I've just learnt on this list. A "regular" curve would be hard to get). May it happen that fluctuations in frequency due to "external" causes such as tides, geomagnetic storms, or so, and not actually affecting the "aging rate", are interpreted as fluctuations in the aging rate? I'm running a simple test comparing an OCXO (option 04E on a military Racal 1992 counter) to rubidium (LPRO), the counter being counting the LPRO. The test is running since about two weeks, and I started recording three days after power up. In the first days the OCXO showed a decreasing drift starting with some 3x10e-10 per day until it reached a stability within +/- 1x10e-10 in the last 5 days (that is, since 5 days back, the counters reads always the same value +/- the occasional uncertainty of the rightmost (11th) digit (10 seconds gate time). The OCXO specs are <= 5x10e-10 per day. I didn't notice whether it is sealed, and won't check right now. I don't expect that the counter will always stay there, and I don't know what to think when the drift (aging rate?) will change. Thanks, 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] Aging rate of crystals
Tom Van Baak wrote: > Rick, > > For these experiments did you remove the 10811 guts from the > outer case? I realize the case is not sealed, but the air gap is > very small; how could humidity get inside so rapidly? > > Did you look into /why/ the 10811 was humidity sensitive? The > resonator and most individual board components are sealed, so > that doesn't leave too much. Maybe the coarse tuning variable > capacitor, which is exposed to air through its 2 mm hole? > > Do you know if most modern high-end OCXO, which are solder > sealed, and which have no screwdriver tuning access hole, are > immune from all humidity variations? > > /tvb I did not remove the 10811 from the case. OTOH, I tried some experiments with so-called "hermetic" epoxy. I think I used the 10811 version with the feedthrus in place of the edge connector. I sealed all the holes and seams etc. I am fairly confident the oscillator was "waterproof", meaning you could dunk it in a bucket of water with no ill effects. In any event, what I found was that the epoxy was not only not hermetic, but it virtually didn't even slow down the frequency shift due to humidity. BTW, the individual board components are definitely NOT sealed, being epoxy dipped or plastic molded. Except for the 2N5179 transistors and some of the glass diodes. I am fairly certain that solder sealed oscillators are actually hermetic and will not be influenced by humidity. Rick Karlquist N6RK ___ 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] Aging rate of crystals
After spending lots of time trying to make passive 'scope probes immune to moisture intrusion, I can say that any hole in an OXCO can will result in moisture effects showing up; it's just a matter of time. While there are PCB coating materials aplenty, they only serve to delay the inevitable. I think the same is true of taping over holes in a can; for a time, it helps, but not for long. Fully sealed assemblies are hard to find, but it's the only way to get the job done. Pete Rawson ___ 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] Aging rate of crystals
> Did you look into /why/ the 10811 was humidity sensitive? The > resonator and most individual board components are sealed, so > that doesn't leave too much. Maybe the coarse tuning variable > capacitor, which is exposed to air through its 2 mm hole? When I was reading Rick's post, I immediately thought of the coarse adjustment hole / cap too. I wonder if plugging it up and taping over the hole would help any? > Do you know if most modern high-end OCXO, which are solder > sealed, and which have no screwdriver tuning access hole, are > immune from all humidity variations? MTI-Milliren has some specials right now, someone could get one of their 250 or 260 series sealed oscillators for < $150 and run some tests... ___ 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] Aging rate of crystals
> At the beginning of the E1938A project, I did some humidity > tests on the 10811. It was fairly sensitive to humidity. > I think I remember being able to get parts in 10^8 shift. ... > At the beginning of the E1938A project, I did a bunch of > characterization of 10811 oscillators. At the Santa Clara > Division, we had first class environmental test chambers > with heating, cooling, humidification, de-humidification, > and nitrogen purge. The nitrogen was also available for > fast cooling. The 10811 response to humidity was very rapid, > like 10 or 15 minutes, almost as fast as the chamber > itself could ramp. This occurred whether going from > dry to humid or the other way around. I don't remember > seeing any slow "tails" on the response. The immediate > humidity response was on the order of a month of aging, > so any humidity related aging effects would be masked. > > Rick Karlquist N6RK Rick, For these experiments did you remove the 10811 guts from the outer case? I realize the case is not sealed, but the air gap is very small; how could humidity get inside so rapidly? Did you look into /why/ the 10811 was humidity sensitive? The resonator and most individual board components are sealed, so that doesn't leave too much. Maybe the coarse tuning variable capacitor, which is exposed to air through its 2 mm hole? Do you know if most modern high-end OCXO, which are solder sealed, and which have no screwdriver tuning access hole, are immune from all humidity variations? /tvb ___ 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] Aging rate of crystals
The dielectric constant of air has a tempco of about 5ppm/C The variation of the dielectric constant of air with humidity is about + 1.4ppm per %RH. The dielectric constant of air has a pressure coefficient of about 100ppm/atm. The rapid variations in frequency may be due to variation of fringing capacitances and the capacitance of any air dielectric trimmer caps with humidity. The time constants for the absorption and desorption of water by epoxies and other plastics may be so long that the effects of the variation of water content of circuit board and other plastics surrounding the oscillator components on oscillator frequency are masked by aging. Bruce ___ 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] Aging rate of crystals
Apart from the humidity theory... 20 years ago I did a masters in material science. One of the major sections of this field is the study of what was then composite materials or now amorphous materials. These are defined as materials having an observable glass transition temperature. The glass transition is a secondary physical transition and can be observed as a discontinuity in the rate of change any one of a number of physical properties as temperature is changed. Primary transitions are phenomena like melting and crystalisation. These materials are often described as visco-elastic, when stretched and released they partly recover and then slowly creep back to the original state at a very slow rate. Convolved with the visco-elasticity is a process called physical ageing, where physical properties change with time. The rate of ageing can be very sensitive to other parameters, moisture absorbing polymers, like nylon and keratin, can change their rate of physical ageing over 10 decades of time depending on their moisture content. Now crystaline materials, quartz, ceramics, most metals do not have glass transition temperatures in our set of conditions. But most plastics, tin/lead alloys are amorphous materials and so would have properties that would change on the timescale of oscillator drift when the temperature is changed. So may be that is where our oscillator drift comes from. And it is possible that a zero moisture content might slow it down considerably, that is shift the rate of physical ageing. I was almost starting to forget all that stuff, I have had no application for it for such a long time. cheers, Neville Michie On 18/02/2008, at 5:26 PM, Richard (Rick) Karlquist wrote: > At the beginning of the E1938A project, I did a bunch of > characterization of 10811 oscillators. At the Santa Clara > Division, we had first class environmental test chambers > with heating, cooling, humidification, de-humidification, > and nitrogen purge. The nitrogen was also available for > fast cooling. The 10811 response to humidity was very rapid, > like 10 or 15 minutes, almost as fast as the chamber > itself could ramp. This occurred whether going from > dry to humid or the other way around. I don't remember > seeing any slow "tails" on the response. The immediate > humidity response was on the order of a month of aging, > so any humidity related aging effects would be masked. > > Rick Karlquist N6RK > > Thomas A. Frank wrote: >>> The best experiment I can think of to prove this is to run the >>> oscillator in a paper bag until it is stable, >>> then trickle a flow of dry nitrogen into the bag for a day or two >>> and watch for oscillator drift as the humidity >>> in the oven drops to extremely low values. >>> It is a pity that I do not have bottled gas on tap any more. >>> cheers, Neville Michie >> >> >> I like your theory, it has a marvelous macroscopic physical component >> to it. >> >> A way to run that test without any bottled gas would be start during >> a very humid spell (the stabilize things at a humid level; say 80% >> RH), then to put the crystal assembly into a sealable plastic >> container (Tupperware for US folks) with a bunch of silica gel or >> other desiccant. >> >> The humidity in the container will drop to well below 20%, and stay >> there until you open the container. That's a pretty decent range to >> work over. >> >> Tom Frank, KA2CDK >> >> >> >> >> ___ >> 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] Aging rate of crystals
At the beginning of the E1938A project, I did a bunch of characterization of 10811 oscillators. At the Santa Clara Division, we had first class environmental test chambers with heating, cooling, humidification, de-humidification, and nitrogen purge. The nitrogen was also available for fast cooling. The 10811 response to humidity was very rapid, like 10 or 15 minutes, almost as fast as the chamber itself could ramp. This occurred whether going from dry to humid or the other way around. I don't remember seeing any slow "tails" on the response. The immediate humidity response was on the order of a month of aging, so any humidity related aging effects would be masked. Rick Karlquist N6RK Thomas A. Frank wrote: >> The best experiment I can think of to prove this is to run the >> oscillator in a paper bag until it is stable, >> then trickle a flow of dry nitrogen into the bag for a day or two >> and watch for oscillator drift as the humidity >> in the oven drops to extremely low values. >> It is a pity that I do not have bottled gas on tap any more. >> cheers, Neville Michie > > > I like your theory, it has a marvelous macroscopic physical component > to it. > > A way to run that test without any bottled gas would be start during > a very humid spell (the stabilize things at a humid level; say 80% > RH), then to put the crystal assembly into a sealable plastic > container (Tupperware for US folks) with a bunch of silica gel or > other desiccant. > > The humidity in the container will drop to well below 20%, and stay > there until you open the container. That's a pretty decent range to > work over. > > Tom Frank, KA2CDK > > > > > ___ > 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] Aging rate of crystals
> The best experiment I can think of to prove this is to run the > oscillator in a paper bag until it is stable, > then trickle a flow of dry nitrogen into the bag for a day or two > and watch for oscillator drift as the humidity > in the oven drops to extremely low values. > It is a pity that I do not have bottled gas on tap any more. > cheers, Neville Michie I like your theory, it has a marvelous macroscopic physical component to it. A way to run that test without any bottled gas would be start during a very humid spell (the stabilize things at a humid level; say 80% RH), then to put the crystal assembly into a sealable plastic container (Tupperware for US folks) with a bunch of silica gel or other desiccant. The humidity in the container will drop to well below 20%, and stay there until you open the container. That's a pretty decent range to work over. Tom Frank, KA2CDK ___ 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] Aging rate of crystals
At the beginning of the E1938A project, I did some humidity tests on the 10811. It was fairly sensitive to humidity. I think I remember being able to get parts in 10^8 shift. The E1938A, having the bridge oscillator circuit, is completely insensitive to humidity and nearly so to temperature (10^-13 per degree C). It's aging is basically the same as the 10811, since the crystals are basically the same (different package). Rick Karlquist N6RK Neville Michie wrote: > This is a theory that I have been thinking about for some time. > A possible physical process for crystal ageing is the desorption of > water from > surfaces in the oscillator circuit. > Most solid surfaces, particularly those with oxygen in the molecular > structure, > have at least a monolayer of water over the surface. > In high vacuum laboratory work you bake glassware at 300*C for 4 > hours in a > hard vacuum to remove this water to prevent future degassing. > > When you have an oven with air interchange to the ambient, the > humidity in the oven becomes very low. For example air at 20*C and > 65% RH > drops to 3.2% RH if heated to 80*C. (the vapour pressure of water is > still 1520 Pascals) > > Relative humidity is a good predictor of the amount of moisture > absorbed and adsorbed > by a solid. > The heating of the oven reduces the relative humidity, so much water > would leave a surface > on warm-up but the last of the water is tightly bound and to reach a > thermodynamic equilibrium under > these conditions is very slow. > > If the air at room temperature had the humidity reduced to 32.5%, > then the RH in the oven > would reduce to 1.6%, so the oscillator would still respond to the > change in humidity. > > The main evidence to support this theory is that it is a plausible > physical process with > slow enough time constants and known hysteresis that could explain > the days it takes > for my HP 10811A to return to the control voltage it formerly > required to be on frequency > after it has been allowed to cool down for 2 days. > The best experiment I can think of to prove this is to run the > oscillator in a paper bag until it is stable, > then trickle a flow of dry nitrogen into the bag for a day or two > and watch for oscillator drift as the humidity > in the oven drops to extremely low values. > It is a pity that I do not have bottled gas on tap any more. > cheers, Neville Michie > > On 16/02/2008, at 7:24 AM, Rick Karlquist wrote: > >> For ovenized crystals, any oven temperature change will >> cause aging to temporarily increase (and may change the >> direction as well). Restabilization may take an hour >> to a day, depending on how much the temperature was changed. >> We haven't noticed that powering up the oscillator or not >> makes a big difference. (This refers to leaving the oven >> on, and turning off the oscillator circuitry. This experiment >> This is a theory that I have been thinking about for some time.is >> easy to do on a 10811 since the supplies are separate.) >> Does that answer your question? >> >> Rick Karlquist N6RK >> >> >> [EMAIL PROTECTED] wrote: >>> Hi all, >>> the aging rate of crystals is known to be not constant. >>> Is there any known external cause affecting the rate, or it is only a >>> matter of casuality? >>> Thanks, >>> 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. >>> >>> >> >> >> >> ___ >> 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] Aging rate of crystals
This is a theory that I have been thinking about for some time. A possible physical process for crystal ageing is the desorption of water from surfaces in the oscillator circuit. Most solid surfaces, particularly those with oxygen in the molecular structure, have at least a monolayer of water over the surface. In high vacuum laboratory work you bake glassware at 300*C for 4 hours in a hard vacuum to remove this water to prevent future degassing. When you have an oven with air interchange to the ambient, the humidity in the oven becomes very low. For example air at 20*C and 65% RH drops to 3.2% RH if heated to 80*C. (the vapour pressure of water is still 1520 Pascals) Relative humidity is a good predictor of the amount of moisture absorbed and adsorbed by a solid. The heating of the oven reduces the relative humidity, so much water would leave a surface on warm-up but the last of the water is tightly bound and to reach a thermodynamic equilibrium under these conditions is very slow. If the air at room temperature had the humidity reduced to 32.5%, then the RH in the oven would reduce to 1.6%, so the oscillator would still respond to the change in humidity. The main evidence to support this theory is that it is a plausible physical process with slow enough time constants and known hysteresis that could explain the days it takes for my HP 10811A to return to the control voltage it formerly required to be on frequency after it has been allowed to cool down for 2 days. The best experiment I can think of to prove this is to run the oscillator in a paper bag until it is stable, then trickle a flow of dry nitrogen into the bag for a day or two and watch for oscillator drift as the humidity in the oven drops to extremely low values. It is a pity that I do not have bottled gas on tap any more. cheers, Neville Michie On 16/02/2008, at 7:24 AM, Rick Karlquist wrote: > For ovenized crystals, any oven temperature change will > cause aging to temporarily increase (and may change the > direction as well). Restabilization may take an hour > to a day, depending on how much the temperature was changed. > We haven't noticed that powering up the oscillator or not > makes a big difference. (This refers to leaving the oven > on, and turning off the oscillator circuitry. This experiment > This is a theory that I have been thinking about for some time.is > easy to do on a 10811 since the supplies are separate.) > Does that answer your question? > > Rick Karlquist N6RK > > > [EMAIL PROTECTED] wrote: >> Hi all, >> the aging rate of crystals is known to be not constant. >> Is there any known external cause affecting the rate, or it is only a >> matter of casuality? >> Thanks, >> 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. >> >> > > > > ___ > 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] Aging rate of crystals
Thanks Rick. I will study the matter a bit more. Meantime I would tell where my question originated from. I was referring to a condition where temperature is assumed to be constant. In the article at http://www.agilent.com/metrology/xtal-policy.shtml (fig. 1) Agilent doesn't refer to temperature as a cause of VARIATION of the aging rate, instead they state that "The apparent aging rate would also vary considerably depending when the measurements were made". So, my question would more precisely be: is there any known cause (beyond temperature) that affects aging rate (that is the speed at which a crystal ages)? Regards, Antonio Iovane I8IOV > For ovenized crystals, any oven temperature change will > cause aging to temporarily increase (and may change the > direction as well). Restabilization may take an hour > to a day, depending on how much the temperature was changed. > We haven't noticed that powering up the oscillator or not > makes a big difference. (This refers to leaving the oven > on, and turning off the oscillator circuitry. This experiment > is easy to do on a 10811 since the supplies are separate.) > Does that answer your question? > > Rick Karlquist N6RK > ___ 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] Aging rate of crystals
For ovenized crystals, any oven temperature change will cause aging to temporarily increase (and may change the direction as well). Restabilization may take an hour to a day, depending on how much the temperature was changed. We haven't noticed that powering up the oscillator or not makes a big difference. (This refers to leaving the oven on, and turning off the oscillator circuitry. This experiment is easy to do on a 10811 since the supplies are separate.) Does that answer your question? Rick Karlquist N6RK [EMAIL PROTECTED] wrote: > Hi all, > the aging rate of crystals is known to be not constant. > Is there any known external cause affecting the rate, or it is only a > matter of casuality? > Thanks, > 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. > > ___ 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.
