Re: [time-nuts] Improving the stability of crystal oscillators
: Bruce Griffiths [EMAIL PROTECTED] To: Don Collie [EMAIL PROTECTED] Sent: Wednesday, October 17, 2007 4:35 PM Subject: Re: [time-nuts] Improving the stability of crystal oscillators Don Collie wrote: Dear Dr Bruce, I am partially depantsed [*only* partially]. Do I have your permission to respond to your points on group? This way either you, or I will be fully depantsed. All the best,...Don. Don That would perhaps be a good idea in that it may be educational to others and any delusions etc may be cured. 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Enough speculation on ground temperatures. The attenuation of cyclic variations of surface temperature die away at an exponential rate with depth. The thermal diffusivity of soils does vary but not so you can not generalise. For daily changes, the temperature variation is attenuated to 1% of the surface swing between 0.3 and 0.6 metres. For the annual swing, the distances are about 20 times greater. I once was investigating a limestone cave climate, and I was delighted by a pure sine wave of temperature that showed up on a data logger after a year of measureing the temperature of the cave roof. It would not have been noticed except that the logger was a high resolution model. It was about 15 metres underground. Higher frequencies have much higher attenuation, so the harmonics of daily and annual cycles are quickly lost. Thermal transients propagate into the ground on a different law, Gauss' Error Function. If the ground is cleared of trees, one hundred years later at a depth of 100 metres or so there will be a record of the change in average soil temperature. The Cave was Saltpetre Cave in Carter Caves Park. Just thought you might like to know. Neville Michie On 15/10/2007, at 1:18 PM, Hal Murray wrote: I've heard there is some depth that building foundations need to be so they don't get winter frost heave that might be on the order of a couple of feet, but that's far different from an constant temperature depth. That depends on where you live. I'm guessing that 10 or 15 feet may be required to get fractional degree temp stability where I am. The Wisconsin data was in loam which I think means a fairly good insulator. They had the widest temperature variation (15 c delta @ 120 cm down). I've got sand and clay after the first foot or so which may be a better thermal conductor implying less variation. The math is the same as for skin depth on RF on metal. The temperature fluctuation decays exponentially with depth. Lower frequencies (years vs days) go deeper. -- These are my opinions, not necessarily my employer's. I hate spam. ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY In a message dated 10/14/2007 23:07:04 Pacific Daylight Time, [EMAIL PROTECTED] writes: Thermal transients propagate into the ground on a different law, Gauss' Error Function. If the ground is cleared of trees, one hundred years later at a depth of 100 metres or so there will be a record of the change in average soil temperature. The Cave was Saltpetre Cave in Carter Caves Park. Just thought you might like to know. Neville Michie Hi Neville, your post made me remember stuff from my University days! Gauss' Error Function is also used to calculate diffusion depth of semiconductors. HP/Agilent makes a semiconductor tester to measure this depth. One interesting fact I remember from this: the form of the diffusion profile depends on the speed (time) of the actual diffusion process into the bulk material. I bet there is a nice analog to temperature transients progressing through soil. I love it when micro and macro effects show mathematical similarities. bye, Said ** See what's new at http://www.aol.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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Dear all, the major problem for the use of a Peltier cell with a quartz oscillator is that the cell maximum operating temperature is of the order of 80 degrees Celsius. This is due to the low melting point of the metal pairs suitable to produce the Peltier effect (reversed thermocouple). The resonator inversion temperature occurs at 70-80 degrees Celsius, depending on the cut angles. A more general problem is that a good temperature controlled oven has high thermal resistance, limited by the dissipation inside the oven. Unfortunately, the Peltier cell has low thermal resistance, which means poor isolation from the oven. This problem is made worse by the joule effect, which always go with the Peltier effect. For this reason, the temperature fluctuations of the Peltier heat sink tend to be larger than the environment fluctuations (unless you use water cooling!). Thus, the thermal fluctuations propagating through the Peltier cell tend to be an amplified version of the environment fluctuation. This phenomenon is dramatic when the Peltier cools down, and a minor problem when the Peltier cell heats up. Very best, Enrico On 13 Oct 2007, at 22:13 , Don Collie wrote: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Has anyone concidered using a small Peltier pile to maintain the crystal`s temparature. I understand that these devices will heat or cool, so it would be possible to maintain the crystal temparature at , say, 25 degrees celcius, over a range of ambient temparatures [perhaps 0 to 70 degrees]. There would be several advantages in this approach. Cheers!,Don Collie jnr. ___ 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. Enrico Rubiola professor of electronics web:http://rubiola.org e-mail: [EMAIL PROTECTED] FEMTO-ST Institute 32 av. de l'Observatoire 25044 Besancon, FRANCE voice: +33(0)381.853940 (E.Rubiola) voice: +33(0)381.853999 (switchboard) fax:+33(0)381.853998 ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY The resonator inversion temperature occurs at 70-80 degrees Celsius, depending on the cut angles. Is there something magic about quartz that has a turnover in the region that just happens to be handy for OCXOs? Or is it the other way around: people chose the cut angle to get a temperature that works well for ovens? Could I cut a crystal with a temperature at (say) 0C or something handy for Peltiers? -- These are my opinions, not necessarily my employer's. I hate spam. ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi Hal, I was thinking of attaching a temparature sensor [AKA Star Treck] to the cold side of a Peltier [what`s the other type? Are they available/better?] pile. and driving the pile from the output of some sort of servo loop to maintain a temparature of ,say , 0 Degree C. If you wanted a double oven, you could heatsink a small oven, containing the crystal, the oscillator, and buffer[s] to this, and use a second servo loop to raise the temparature of this to 25 Degrees C working against the Peltier. In this way, you could maintain the crystal, and circuitry at 25 Deg C., over an ambient temparature of 0 to ,say 70 Deg C. Yes, you can cut a crystal to have an inversion temp at 25Deg C. [well certainly with an AT cut - I`m not sure about the SC cut.] Cheers,Don C. - Original Message - From: Hal Murray [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tuesday, October 16, 2007 5:49 AM Subject: Re: [time-nuts] Improving the stability of crystal oscillators ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY The resonator inversion temperature occurs at 70-80 degrees Celsius, depending on the cut angles. Is there something magic about quartz that has a turnover in the region that just happens to be handy for OCXOs? Or is it the other way around: people chose the cut angle to get a temperature that works well for ovens? Could I cut a crystal with a temperature at (say) 0C or something handy for Peltiers? -- These are my opinions, not necessarily my employer's. I hate spam. ___ 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. -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.488 / Virus Database: 269.14.12/1072 - Release Date: 10/15/2007 5:55 PM ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY This is something I have thought about but never did any experimentation. With the low cost and increased availability of thermoelectric coolers, I am interested in pursuing this concept. The unfortunate thing is that the crystals are ground for 25C or the higher turnover temperature point. If someone has a crystal that has drifted, it may be a good candidate for experimentation. Another thought would be to let the crystal operate at its natural frequency, divide it down to 1 or ten Hz and then phase lock a more convenient crystal frequency to the low pulse rate. The idea is to save an otherwise aged and well performing crystal. John WA4WDL - Original Message - From: Tom Van Baak [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Monday, October 15, 2007 10:12 PM Subject: Re: [time-nuts] Improving the stability of crystal oscillators As far as I can tell, temperature curve plots for quartz typically show both an upper and a lower turnover point (for example, see the pages below). Since the upper is well above maximum ambient, it makes sense that this point is used in O[ven]CXO. The question is -- does anyone know if the lower turnover point (LTP) is ever used? I ask because I heard that a quartz oscillator might have slightly better short-term stability at the LTP compared to the UTP. If so, this might argue for the extra trouble of using TEC for cooling in some low-noise applications. /tvb http://www.ieee-uffc.org/freqcontrol/tutorials/vig3/vig3_files/slide0164.htm http://www.ieee-uffc.org/freqcontrol/tutorials/vig3/vig3_files/slide0306.htm ___ 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] Improving the stability of crystal oscillators
Don Collie wrote: Hi Hal, I was thinking of attaching a temparature sensor [AKA Star Treck] to the cold side of a Peltier [what`s the other type? Are they available/better?] pile. and driving the pile from the output of some sort of servo loop to maintain a temparature of ,say , 0 Degree C. If you wanted a double oven, you could heatsink a small oven, containing the crystal, the oscillator, and buffer[s] to this, and use a second servo loop to raise the temparature of this to 25 Degrees C working against the Peltier. In this way, you could maintain the crystal, and circuitry at 25 Deg C., over an ambient temparature of 0 to ,say 70 Deg C. Yes, you can cut a crystal to have an inversion temp at 25Deg C. [well certainly with an AT cut - I`m not sure about the SC cut.] Cheers,Don C. - Original Message - Don With such a wide swing in the temperature differeence across the Peltier stack, you will need to adjust the PID loop parameters to maintain optimum control. A fixed set of parameters is only useful for a temperature range of up to 10C. The Peltier stack performance varies significantly with the temperature difference across the stack. Consequently you also need to sense the peltier device heatsink temperature. 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY The required depth depends on the soil diffusivity and the temperature stability required. It is instructive to install thermometers at depth intervals of a foot or so and record the temperature fluctuations experienced by each thermometer. This was first done around 1860 by Forbes. I repeated the experiment in 1966. There was an interesting bit in the last Agilent Measurement Journal about a product that uses an ordinary communications-grade fiber as a thermometer. From what I remember, they send a laser pulse down the fiber, then look at the backscatter, correlating time-of-flight with the Raman-scattering lines (Stokes and anti-Stokes). One of those spectral lines is temperature-dependent while the other isn't, so by recording the separation, they end up with is a graph of temperature versus distance along the fiber, gathering up to a few kilometers' worth of data with what looked like sub-meter resolution. No doubt this effect is old hat to physicists on the list, but I'd never heard how it worked before. So if you buried a fiber like this, you'd presumably get a great picture of what happens with temperature at various depths. Plotting the temperature-versus-distance on a waterfall display gives a nice diurnal picture. The article used it to study water temperature along the course of a stream, but you could think of plenty of other uses for 2D remote temperature sensing. -- john, KE5FX ___ 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] Improving the stability of crystal oscillators
From: John Miles [EMAIL PROTECTED] Subject: Re: [time-nuts] Improving the stability of crystal oscillators Date: Sun, 14 Oct 2007 14:15:10 -0700 Message-ID: [EMAIL PROTECTED] ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY The required depth depends on the soil diffusivity and the temperature stability required. It is instructive to install thermometers at depth intervals of a foot or so and record the temperature fluctuations experienced by each thermometer. This was first done around 1860 by Forbes. I repeated the experiment in 1966. There was an interesting bit in the last Agilent Measurement Journal about a product that uses an ordinary communications-grade fiber as a thermometer. From what I remember, they send a laser pulse down the fiber, then look at the backscatter, correlating time-of-flight with the Raman-scattering lines (Stokes and anti-Stokes). One of those spectral lines is temperature-dependent while the other isn't, so by recording the separation, they end up with is a graph of temperature versus distance along the fiber, gathering up to a few kilometers' worth of data with what looked like sub-meter resolution. No doubt this effect is old hat to physicists on the list, but I'd never heard how it worked before. So if you buried a fiber like this, you'd presumably get a great picture of what happens with temperature at various depths. Plotting the temperature-versus-distance on a waterfall display gives a nice diurnal picture. The article used it to study water temperature along the course of a stream, but you could think of plenty of other uses for 2D remote temperature sensing. Bell Labs have made measures on soil temperature at different deps and also fiber-delay as it varies with temperature. As it happends, the delay is part due to fiber length change due to temperature and most part due to change of delay due to change in dielectrics which converts into changes in the wave- equation. It naturally depends on temperature, laser wavelength and accumulates over distance. I haven't seen any paper on non-chromatic delay shifts, but I haven't looked too closely. Cheers, Magnus ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi Bruce: All the papers are for depths on the order of a few feet, aimed at plant growth, nevertheless in all cases the temperature was changing by at least 1 deg c at the deepest depth recorded. I've heard there is some depth that building foundations need to be so they don't get winter frost heave that might be on the order of a couple of feet, but that's far different from an constant temperature depth. I'm guessing that 10 or 15 feet may be required to get fractional degree temp stability where I am. The Wisconsin data was in loam which I think means a fairly good insulator. They had the widest temperature variation (15 c delta @ 120 cm down). I've got sand and clay after the first foot or so which may be a better thermal conductor implying less variation. Have Fun, Brooke Clarke http://www.PRC68.com http://www.precisionclock.com http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam Bruce Griffiths wrote: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Brooke Clarke wrote: Hi Bruce: Details on your experiment please. Hole/pipe diameter, material? Depth? Delta T at different depths vs surface ambient? Soil type? Have Fun, Brooke Clarke Brooke Unable as yet to find my data, it was published in some very obscure publication if I remember correctly. However there was extensive series of records kept in England from the time of Lord Kelvin. More recent data is available from the US forest service among others: http://ncrs.fs.fed.us/pubs/rn/rn_nc032.pdf Above is for Wisconsin, not directly applicable to California. http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?letter=.classic=YESbibcode=1952AuSRA...5..303Wpage=type=SCREEN_VIEWdata_type=PDF_HIGHsend=GETfiletype=.pdf http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?letter=.classic=YESbibcode=1952AuSRA...5..303Wpage=type=SCREEN_VIEWdata_type=PDF_HIGHsend=GETfiletype=.pdf Above paper by CSIRO is for an Australian site. Analysis is fairly comprehensive. http://www.mmm.ucar.edu/mm5/lsm/soil.pdf http://www.ias.ac.in/epsci/mar2002/Esb1439.pdf 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. ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I've heard there is some depth that building foundations need to be so they don't get winter frost heave that might be on the order of a couple of feet, but that's far different from an constant temperature depth. That depends on where you live. I'm guessing that 10 or 15 feet may be required to get fractional degree temp stability where I am. The Wisconsin data was in loam which I think means a fairly good insulator. They had the widest temperature variation (15 c delta @ 120 cm down). I've got sand and clay after the first foot or so which may be a better thermal conductor implying less variation. The math is the same as for skin depth on RF on metal. The temperature fluctuation decays exponentially with depth. Lower frequencies (years vs days) go deeper. -- These are my opinions, not necessarily my employer's. I hate spam. ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi Don: They are very inefficient to the point that a system that's supposed to cool something may heat it because of all the heat generated by the module. It takes a huge amount of heat sinking or liquid cooling to get them to work. Have Fun, Brooke Clarke http://www.PRC68.com http://www.precisionclock.com http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam Don Collie wrote: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Has anyone concidered using a small Peltier pile to maintain the crystal`s temparature. I understand that these devices will heat or cool, so it would be possible to maintain the crystal temparature at , say, 25 degrees celcius, over a range of ambient temparatures [perhaps 0 to 70 degrees]. There would be several advantages in this approach. Cheers!,Don Collie jnr. ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Brooke Clarke wrote: Hi: Something I've been thinking about is attaching a large thermal mass of aluminum to the crystal and it's oscillator then surrounding that with insulation. Then surround that with a thin copper layer. Temperature sensors on the copper and aluminum. If the thermal time constant could be made very close to 24 hours, or integer multiples of that, it might be possible to predict the inner temperature allowing compensation. Has this already been done? Brooke Why stop there? Try burying the oscillator under 6ft or so of soil. The daily temperature fluctuations at this depth are very small. 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Nah, not for this application. A Peltier module typically has a COP of 1. That is, it moves a watt of energy for each watt consumed. Thus, for each watt moved, two watts have to be dissipated to air. I can't imagine a well-insulated quartz oscillator needing more than a watt or two of cooling at the most. A heat sink capable of handling 4-5 watts should do the job just fine. Don: I've seen peltier-controlled ambient ovens before but I can't recall the details. I'm fairly sure one was a Fluke precision voltage transfer standard in which the zener reference diode was controlled to a constant temperature. The advantage of using room temperature, e.g., 70 deg F, is that under most conditions, the peltier module is doing little to nothing, perhaps just ridding the ovenized unit of the few milliwatts dissipated in the circuit itself. I've used multiple cascaded modules to cool a nuclear detector (Silicon surface barrier diode) to reduce its noise. Not as good as LN2 but much cheaper to operate. John On Sat, 13 Oct 2007 13:26:52 -0700, Brooke Clarke [EMAIL PROTECTED] wrote: Hi Don: They are very inefficient to the point that a system that's supposed to cool something may heat it because of all the heat generated by the module. It takes a huge amount of heat sinking or liquid cooling to get them to work. Don Collie wrote: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Has anyone concidered using a small Peltier pile to maintain the crystal`s temparature. I understand that these devices will heat or cool, so it would be possible to maintain the crystal temparature at , say, 25 degrees celcius, over a range of ambient temparatures [perhaps 0 to 70 degrees]. There would be several advantages in this approach. -- John De Armond See my website for my current email address http://www.neon-john.com http://www.johndearmond.com -- best little blog on the net! Tellico Plains, Occupied TN I like you ... you remind me of me when I was young and stupid. ___ 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] Improving the stability of crystal oscillators
Brooke Clarke wrote: Hi Don: They are very inefficient to the point that a system that's supposed to cool something may heat it because of all the heat generated by the module. It takes a huge amount of heat sinking or liquid cooling to get them to work. Have Fun, Brooke Clarke Brooke The answer depends on how much heat has to be pumped. Peltier heat pumps are quite effective as long as the amount of heat to be pumped is relatively small. With a 70W module a water cooled or blown heatsink is advisable. With a 1W module an aircooled heatsink is adequate. Small Peltier heatpump have been used to stabilise the temperature of photodiodes etc (HP used them in the 8153 light wave multimeter optical detector heads). They have also been successfully used to stabilise the temperature of a baseplate with devices dissipating 10W or so attached to the baseplate. Peltier modules are also used in small aerogel insulated refrigerators and in drink coolers. One potential problem is that low power peltier modules are very small so that a high thermal conductivity heat spreader is desirable to improve the temperature uniformity. Single stage peltier modules are quite thin so that a thick low thermal resistance heat-spreader/spacer is required to allow a sufficiently thick layer on insulation to be used. 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Don Collie [EMAIL PROTECTED] wrote: Has anyone concidered using a small Peltier pile to maintain the crystal`s temparature. I understand that these devices will heat or cool, so it would be possible to maintain the crystal temparature at , say, 25 degrees celcius, over a range of ambient temparatures [perhaps 0 to 70 degrees]. There would be several advantages in this approach. Cheers!,Don Collie jnr. Overall, the Petier devices don't heat or cool, just heat :-). I don't know about crystal oven applications, but condensation on the cold side has ruled out several applications for Peltiers at my day job. Tim. ___ 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] Improving the stability of crystal oscillators
Sam Harris (SK) did that over 40 years ago. It provided a stable reference for his pioneering work in Moonbounce Communication. 73, Dick, W1KSZ/7 -Original Message- From: Bruce Griffiths [EMAIL PROTECTED] Sent: Oct 13, 2007 2:44 PM To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Improving the stability of crystal oscillators Brooke Clarke wrote: Hi: Something I've been thinking about is attaching a large thermal mass of aluminum to the crystal and it's oscillator then surrounding that with insulation. Then surround that with a thin copper layer. Temperature sensors on the copper and aluminum. If the thermal time constant could be made very close to 24 hours, or integer multiples of that, it might be possible to predict the inner temperature allowing compensation. Has this already been done? Brooke Why stop there? Try burying the oscillator under 6ft or so of soil. The daily temperature fluctuations at this depth are very small. 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. ___ 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] Improving the stability of crystal oscillators
I doug up and included below a time-nuts email from a couple of years ago on improving oscillator stability, with some thoughts from Jack Kusters, Tom Clark, and Brooke Clarke. Also, there's a good history of high precision oscillators at: http://www.ieee-uffc.org/fc_history/norton.html Regards, Bill Powell af4jg FROM: [EMAIL PROTECTED] newmsg.cgi?mbx=Main[EMAIL PROTECTED] | Save Address javascript:document.SaveAddress.submit() DATE: Wed, 26 Oct 2005 13:20:14 -0700 TO: [EMAIL PROTECTED], time-nuts@febo.com SUBJECT: RE: [time-nuts] Xtal Oscillator Aging Hi, I posed this question to Jack Kusters, now retired from HP/Agilent. He and Charles Adams commercialized the SC-cut crystal for HP in the 10811A oscillator. He gave me permission to post his response on the reflector. Jim Johnson [EMAIL PROTECTED] === Hi Jim, In addition to everything Tom Clark said (I agree in general with his explanation), there is another aging mechanism associated with stress. When the crystal blank is manufactured, it is sawn, lapped, ground, etched, and otherwise abused. All of this produces stress in the blank. In addition, there are mounting stresses that arise because of the way the blank is mounted on its header, surface stresses that develop because the electrode material when evaporated and then condensed on the surface shrinks as it cools. All of these result in long-term aging as these stresses need to equilibrate out. In addition, there are other stress related mechanisms that may result in either long- or short- term aging. The quartz material is anisotropic, the mounts, electrode material are isotropic. So, lets assume that we've had the crystal at an elevated, constant temperature. Over a period of time, all stresses, material, mount, electrode, cracks, etc. equilibrate to their lowest energy level and it appears that aging has stopped. Now, take it down in temperature. The anisotropic quartz and the isotropic mount and electrode, have different contraction rates, so the overall system now has a new set of stresses. Let the unit come to full equilibrium at the new, lower temperature. Now take it up in temperature to where it was before. Now we see a whole new set of aging and stress relief. The only virtue is that aging due to cracks and material stress from manufacturing processes should be mostly gone, so the unit should come to equilibrium much faster. One further comment, glass sealed crystals are not necessarily the best way to seal a crystal. It takes heat from a source sufficiently elevated in temperature to melt the glass. This tends to cause contaminents to migrate from the area being sealed to a cooler spot in the package, usually the crystal. Contaminents come from gasses from the torch or from junk trapped in the glass. The cleanest mount one can do is a cold-weld seal under proper conditions. For example, the HP crystals were put into a vacuum furnace, heated to 300+ deg-C overnite at 10E-7 torr with the can stored next to the crystal. After reducing the temperature to about 80-84 deg-C, the crystal was frequency plated to within several parts in 10E7. After that, the mount was placed in the can, the temperature raised up to about 150 deg-C, stabilised in temperature and vacuum, then cold-welded. Done properly, there is essentially no contamination inside the crystal assembly, most of the other stresses are gone, and the typical HP SC-cut would reach an aging rate of better than 1E-7 per day, within the first 5 days. Best regards, Jack Kusters == -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Tom Clark, W3IWI Sent: Sunday, October 23, 2005 9:21 PM To: time-nuts@febo.com Subject: [time-nuts] Xtal Oscillator Aging Brooke (no relation) commented Hi Richard: It's my understanding that this optimization can be done by changing the oscillator power level at the crystal. In the case of the 32768 Hz watch crystal, it must be run a very low power and it has a very low aging rate when compared to higher frequency crystals that are typically run at higher power levels. I think this is related to the crystal throwing off atoms, so more power means more acceleration and more atoms thrown off. Have Fun, Brooke Clarke, N6GCE It has nothing to do with throwing off atoms. A Xtal is actually a mechanical oscillator, with the quartz slab vibrating (in either its fundamental mode, or on an odd overtone); quartz is a piezo-electric material so the voltage across the pins of the xtal has a direct connection to the mechanical vibration. When an xtal oscillator starts up, the associated amplifier generates noise, which then starts the xtal vibrating, which generates signal at the right frequency and a feedback loop is set up. When you
Re: [time-nuts] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi Dick: From what I can Google he built maybe the first parametric amplifier but haven't come across details on the crystal temp stabilization. Do you have info about that? Because of the year involved I think he must have just used the long time constant to slow down the changes, or was he actually using the time of day as a function of frequency? Have Fun, Brooke Clarke, N6GCE http://www.PRC68.com http://www.precisionclock.com http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam Richard W. Solomon wrote: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Sam Harris (SK) did that over 40 years ago. It provided a stable reference for his pioneering work in Moonbounce Communication. 73, Dick, W1KSZ/7 -Original Message- From: Bruce Griffiths [EMAIL PROTECTED] Sent: Oct 13, 2007 2:44 PM To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Improving the stability of crystal oscillators Brooke Clarke wrote: Hi: Something I've been thinking about is attaching a large thermal mass of aluminum to the crystal and it's oscillator then surrounding that with insulation. Then surround that with a thin copper layer. Temperature sensors on the copper and aluminum. If the thermal time constant could be made very close to 24 hours, or integer multiples of that, it might be possible to predict the inner temperature allowing compensation. Has this already been done? Brooke Why stop there? Try burying the oscillator under 6ft or so of soil. The daily temperature fluctuations at this depth are very small. 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. ___ 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] Improving the stability of crystal oscillators
Thanks for that John. I`ve always wanted to play arround with one of these [Peltier] modules. They can now be bought quite cheaply. I envisage a double oven, with the inner oven heated [to 25 degrees], by conventional means, while the Peltier pile cools the inner oven. This way you could use a precision temparature regulator for the inner oven, while the outer oven would only have to cool. You wouldn`t be talking too many pumped watts, here. FWIW etc.,...Don C. - Original Message - From: Neon John [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, October 14, 2007 11:19 AM Subject: Re: [time-nuts] Improving the stability of crystal oscillators ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Nah, not for this application. A Peltier module typically has a COP of 1. That is, it moves a watt of energy for each watt consumed. Thus, for each watt moved, two watts have to be dissipated to air. I can't imagine a well-insulated quartz oscillator needing more than a watt or two of cooling at the most. A heat sink capable of handling 4-5 watts should do the job just fine. Don: I've seen peltier-controlled ambient ovens before but I can't recall the details. I'm fairly sure one was a Fluke precision voltage transfer standard in which the zener reference diode was controlled to a constant temperature. The advantage of using room temperature, e.g., 70 deg F, is that under most conditions, the peltier module is doing little to nothing, perhaps just ridding the ovenized unit of the few milliwatts dissipated in the circuit itself. I've used multiple cascaded modules to cool a nuclear detector (Silicon surface barrier diode) to reduce its noise. Not as good as LN2 but much cheaper to operate. John On Sat, 13 Oct 2007 13:26:52 -0700, Brooke Clarke [EMAIL PROTECTED] wrote: Hi Don: They are very inefficient to the point that a system that's supposed to cool something may heat it because of all the heat generated by the module. It takes a huge amount of heat sinking or liquid cooling to get them to work. Don Collie wrote: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Has anyone concidered using a small Peltier pile to maintain the crystal`s temparature. I understand that these devices will heat or cool, so it would be possible to maintain the crystal temparature at , say, 25 degrees celcius, over a range of ambient temparatures [perhaps 0 to 70 degrees]. There would be several advantages in this approach. -- John De Armond See my website for my current email address http://www.neon-john.com http://www.johndearmond.com -- best little blog on the net! Tellico Plains, Occupied TN I like you ... you remind me of me when I was young and stupid. ___ 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. -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.488 / Virus Database: 269.14.9/1069 - Release Date: 10/13/2007 7:26 PM ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Brooke Clarke wrote: Hi Bruce: I've also looked into drilling a hole (garden hose, 90 deg fitting pipe with end smashed flat to make a nozzle will easily drill as deep as the pipe is long). Then using a short length of capped copper pipe at the bottom and the rest PVC. Like I think here in California wine country 4 feet would be plenty deep. But this method only works at your home location. Not too good for a clock that will be sent to someone else. I think the long time constant method can be done in a few cubic inches. Have Fun, Brooke Clarke Brooke The required depth depends on the soil diffusivity and the temperature stability required. It is instructive to install thermometers at depth intervals of a foot or so and record the temperature fluctuations experienced by each thermometer. This was first done around 1860 by Forbes. I repeated the experiment in 1966. 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] Improving the stability of crystal oscillators
Hi Bruce: Details on your experiment please. Hole/pipe diameter, material? Depth? Delta T at different depths vs surface ambient? Soil type? Have Fun, Brooke Clarke http://www.PRC68.com http://www.precisionclock.com http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam Bruce Griffiths wrote: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Brooke Clarke wrote: Hi Bruce: I've also looked into drilling a hole (garden hose, 90 deg fitting pipe with end smashed flat to make a nozzle will easily drill as deep as the pipe is long). Then using a short length of capped copper pipe at the bottom and the rest PVC. Like I think here in California wine country 4 feet would be plenty deep. But this method only works at your home location. Not too good for a clock that will be sent to someone else. I think the long time constant method can be done in a few cubic inches. Have Fun, Brooke Clarke Brooke The required depth depends on the soil diffusivity and the temperature stability required. It is instructive to install thermometers at depth intervals of a foot or so and record the temperature fluctuations experienced by each thermometer. This was first done around 1860 by Forbes. I repeated the experiment in 1966. 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. ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Brooke Clarke wrote: Hi Bruce: Details on your experiment please. Hole/pipe diameter, material? Depth? Delta T at different depths vs surface ambient? Soil type? Have Fun, Brooke Clarke Booke I will try to find the data, but it was 41 years ago and may take some time. Location was Palmerston North NZ. Not sure of soil type, however flat region not too far (within 1km or so) from a river. If I remember correctly an access shaft was dug and thermometers were inserted into the soil at the sides of the hole. The leads were bought to the surface and the shaft/hole carefully backfilled and left to settle for some weeks. All measurements were logged manually. 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] Improving the stability of crystal oscillators
Brooke Clarke wrote: Hi Bruce: Details on your experiment please. Hole/pipe diameter, material? Depth? Delta T at different depths vs surface ambient? Soil type? Have Fun, Brooke Clarke Brooke Unable as yet to find my data, it was published in some very obscure publication if I remember correctly. However there was extensive series of records kept in England from the time of Lord Kelvin. More recent data is available from the US forest service among others: http://ncrs.fs.fed.us/pubs/rn/rn_nc032.pdf Above is for Wisconsin, not directly applicable to California. http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?letter=.classic=YESbibcode=1952AuSRA...5..303Wpage=type=SCREEN_VIEWdata_type=PDF_HIGHsend=GETfiletype=.pdf http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?letter=.classic=YESbibcode=1952AuSRA...5..303Wpage=type=SCREEN_VIEWdata_type=PDF_HIGHsend=GETfiletype=.pdf Above paper by CSIRO is for an Australian site. Analysis is fairly comprehensive. http://www.mmm.ucar.edu/mm5/lsm/soil.pdf http://www.ias.ac.in/epsci/mar2002/Esb1439.pdf 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I used to use the clipon posistors to stabilise my crystals (the Murata BM500N previously mentioned) but after seeing some results on what temperature they really stabilise at versus what they should stabilise at i moved on to the heater controller design by John Hazell at http://www.microwaves.dsl.pipex.com/mk2/mk2.pdf note in recent iterations the crystal is embedded in the aluminium block After using the calibration technique he mentions to operate the crystal at the knee point oscillators have had adequate stability for 134GHz local oscillator usage Dave Message: 1 Date: Wed, 10 Oct 2007 10:14:28 -0700 (PDT) From: Tom Clifton [EMAIL PROTECTED] Subject: [time-nuts] Improving the stability of crystal oscillators To: time-nuts@febo.com Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=iso-8859-1 While the website is not explicitly about frequency measurement, there is an interesting bit on improving the stability of crystal oscillators with external heater controllers. While it may not be suitable for long term high stability control it might be suitable for many other purposes. http://www.qrss.thersgb.net/Crystal-Ovens.html The main page is also a good read: http://www.qrss.thersgb.net/Receiving-QRSS.html#Introduction ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi All, I am not trying to start an argument, but I would like to point out that PID controllers are only good at controlling a certain class of system. For a system that has a coal truck that must dump its coal down a hole, the system has mass, velocity and distance, all the qualities to get a perfectly damped system with PID control. For thermal control, the function is more likely to be a Bessel Function, and a Z transform filter is more likely to find a match. In any case, PID controllers are often to be found in totally unsuitable situations giving worse control than even a bang-bang controller. The thermal block controllers work well because of the dominant integrating effect of the block, the time delay for a heat front to propagate through the block is the only concern for instability. When instability is a problem I relocate the thermistor closer to the heater, giving a marginal degree of under- control. Because the block is well insulated it soon becomes very close to isothermal. cheers, Neville Michie On 11/10/2007, at 3:08 PM, Bruce Griffiths wrote: Neville Michie wrote: I have made several ovens for oscillators over the years. The recipe is: get a piece of aluminium big enough to contain the oscillator, voltage regulator and first stage amplifier. With a mill remove the shapes of each component. Bolt a large power transistor, large power fets are best, to the outside of the block as a heater, and it is run off the unregulated input power. Judicious selection of a component decides the start-up current. Make a plate to cover the excavation for the components, and bolt it down. The circuit can be made with discrete transistors in the most unstable looking amplifier ever seen, alternating NPN and PNP transistors, connected directly to each other with load resistors. The main temperature sensor is a resistor bridge with a high value glass encapsulated thermistor. These are available a several trade houses. The amplifier is also temperature sensitive, but is within the thermal loop. The thermistor bridge gives a very large signal ~ 50mV per degree. Gain may have to be backed off if thermal oscillations do not die down, but the metal block acts as an integrator and the circuits are very easy to get high gain and sensitivity. The whole block is packed in two inches of foam insulation, my 1MHz oscillator only draws about 80 mA at 12 volts. The temperature is set to 40 C. The stability of the oscillator is very good, but as I have not yet got a disciplined oscillator going I dont know which is drifting, the HP 10811 in my frequency counter or the 1MHz oscillator. After a year, the difference is currently 0.3 ppm. cheers Neville Michie Neville A correctly tuned PID control loop should allow even tighter temperature control. A boostrapped oven like that used by Wenzel should be even better. (http://www.wenzel.com/documents/Sub-pico%20Multiplier.pdf). Despite Wenzel's claims this type of oven isn't new it was used for portable standard cell enclosures decades ago. 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. ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Maybe because it was written back in 1930's, but one of the better discussions of quartz temperature control, including considerations of insulation and isothermal layers (attenuation and conduction) are in the patents for the old double oven General Radio frequency standard: http://www.leapsecond.com/museum/gr676b-50kc/ http://www.leapsecond.com/museum/gr676b-50kc/US1967185.pdf /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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Neville Michie wrote: Hi All, I am not trying to start an argument, but I would like to point out that PID controllers are only good at controlling a certain class of system. For a system that has a coal truck that must dump its coal down a hole, the system has mass, velocity and distance, all the qualities to get a perfectly damped system with PID control. For thermal control, the function is more likely to be a Bessel Function, and a Z transform filter is more likely to find a match. In any case, PID controllers are often to be found in totally unsuitable situations giving worse control than even a bang-bang controller. The thermal block controllers work well because of the dominant integrating effect of the block, the time delay for a heat front to propagate through the block is the only concern for instability. When instability is a problem I relocate the thermistor closer to the heater, giving a marginal degree of under- control. Because the block is well insulated it soon becomes very close to isothermal. cheers, Neville Michie Neville If a purely proportional control loop has such great performance why does the 10811A use a PI temperature controller and the E1938A use a PII^2 D controller? Surely the finite offset between the setpoint and actual temperature achieved by a proportional controller is a source of long term temperature instability? If one uses resistive heating then some linearisation improves the performance as the heat from the heating element is proportional to the square of the voltage across the heating element. A state space controller may give improved performance but PI(10811A), PID and PII^2 D(E1938A) controllers seem to work well when used to regulate crystal oscillator temperatures. 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] Improving the stability of crystal oscillators
Neville Michie wrote: I am not trying to start an argument, but I would like to point out that PID controllers are only good at controlling a certain class of system. The thermal block controllers work well because of the dominant integrating effect of the block, the time delay for a heat front to propagate through the block is the only concern for instability. When instability is a problem I relocate the thermistor closer to the heater, giving a marginal degree of under- control. Because the block is well insulated it soon becomes very close to isothermal. cheers, Neville Michie I would like to point out that the E1938A uses a PID controller and has a *transient* thermal gain of many 1000's not to mention a static gain that has in some cases exceeded 1,000,000 for a single oven. Your last statement is not generally true. The block cannot be well insulated because of the thermal overhead of the oven circuitry (the heat has to escape). I explained in my 1997 FCS paper how to achieve the isothermal condition, which is achieved by symmetry rather than high amounts of insulation. The E1938A oven works quite well if the insulation is omitted or replaced by poor insulation, except that it consumes more power. 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY The 10811 has an ANALOG oven control loop. The gain is set to be just below the oscillation point. This is due to the stability limits dictated by the oven mass and (believe it or not) the size of integrator capacitor that can physically fit. If you want to soup up at 10811 oven, externally wire in a larger capacitor in parallel and change the resistors to increase the gain. The 10811 designers did the best they could with what they had to work with, but you don't want to blindly copy them in new applications. BTW, do not use a metalized plastic integrator capacitor. Must be foil type. I am extremely happy with the PII^2D control loop on the E1938A (I didn't design it, only tested it). I can't imagine anything being better. Rick Karlquist N6RK Bruce Griffiths wrote: If a purely proportional control loop has such great performance why does the 10811A use a PI temperature controller and the E1938A use a PII^2 D controller? Surely the finite offset between the setpoint and actual temperature achieved by a proportional controller is a source of long term temperature instability? If one uses resistive heating then some linearisation improves the performance as the heat from the heating element is proportional to the square of the voltage across the heating element. A state space controller may give improved performance but PI(10811A), PID and PII^2 D(E1938A) controllers seem to work well when used to regulate crystal oscillator temperatures. 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. ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY At HP, in the 90's, we did a lot of brainstorming about vacuum ovens. This never seemed to make sense to us. If you actually achieve high amounts of thermal resistance, then you can't get the heat out of the oven. And if you don't, why bother with a vacuum. Also, a vacuum only helps if you do everything else you need to do to make a true Dewar (thermos bottle), like having mirrored surfaces, etc. Finally, having a vacuum means that nothing that outgasses can be used in the oscillator. Maybe Vectron has figured out something we didn't think of or has sufficiently difference constraints that a vacuum makes sense for them. Rick Karlquist N6RK [EMAIL PROTECTED] wrote: Today there are some interesting new technologies which allow small double, or even tripple (not sure if that makes sense) ovens to be built. Vectron for example just had a lead-article in RFDesign magazine introducing their newest evacuated OCXO's. _http://rfdesign.com/vlf_to_uhf/time_and_frequency/709RFDF1.pdf_ (http://rfdesign.com/vlf_to_uhf/time_and_frequency/709RFDF1.pdf) They claim stabilities on the order of 2E-07 over a very wide temp range of -40 to +85C in a DIP14 can. The 1/2 size DIP8 can is supposed to be available end of the year with similar performance. Those small cans and wide operating ranges should make it possible to build a nice small and inexpensive oven. If one can get a true thermal gain of 1000+, then that would theoretically mean stabilities approaching 2E-010 over temperature. That's 1.6E-012 per degree Celcius. bye, Said ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi Tom: Very interesting. How about building a circuit to drive those GR crystals? The same man is the inventor of all four of the early GR patents, James Kilton Clapp, of Clapp Oscillator fame. http://en.wikipedia.org/wiki/Clapp_oscillator In the 1930s GR patents he's showing an inductor in series with the crystal and Wiki dates the Clapp Oscillator 1948 where a capacitor is in series. Have Fun, Brooke Clarke http://www.PRC68.com http://www.precisionclock.com http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam Tom Van Baak wrote: Maybe because it was written back in 1930's, but one of the better discussions of quartz temperature control, including considerations of insulation and isothermal layers (attenuation and conduction) are in the patents for the old double oven General Radio frequency standard: http://www.leapsecond.com/museum/gr676b-50kc/ http://www.leapsecond.com/museum/gr676b-50kc/US1967185.pdf /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. ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY On 11/10/2007, at 10:23 PM, Bruce Griffiths wrote: If one uses resistive heating then some linearisation improves the performance as the heat from the heating element is proportional to the square of the voltage across the heating element. If you use a transistor as a heater, the full supply voltage is across the element all the time, so heating is proportional to the current flowing. Neville ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Neville Michie wrote: If you use a transistor as a heater, the full supply voltage is across the element all the time, so heating is proportional to the current flowing. Neville Neville However using a transistor has the disadvantage of a small area heat source rather than the large area heat source possible with a heater winding. Using a small area heat source produces significant temperature gradients. 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY [EMAIL PROTECTED] wrote: Hi Rick, thanks for the pointers to the E1938A oven quality. Today there are some interesting new technologies which allow small double, or even tripple (not sure if that makes sense) ovens to be built. Vectron for example just had a lead-article in RFDesign magazine introducing their newest evacuated OCXO's. _http://rfdesign.com/vlf_to_uhf/time_and_frequency/709RFDF1.pdf_ (http://rfdesign.com/vlf_to_uhf/time_and_frequency/709RFDF1.pdf) They claim stabilities on the order of 2E-07 over a very wide temp range of -40 to +85C in a DIP14 can. The 1/2 size DIP8 can is supposed to be available end of the year with similar performance. Those small cans and wide operating ranges should make it possible to build a nice small and inexpensive oven. If one can get a true thermal gain of 1000+, then that would theoretically mean stabilities approaching 2E-010 over temperature. That's 1.6E-012 per degree Celcius. bye, Said Said The lack of radiation shields and an isothermal block enclosing the oscillator components within the vacuum will surely reduce the performance somewhat. 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] Improving the stability of crystal oscillators
We went through this tradeoff on the E1938A. Resistive heaters can be distributed. However, it is very inefficient to drive them with transistors, because then you waste a lot of power heating the transistors, which is waste heat if resistive heating is used. Prior to the 10544, they just put up with this. The 10544 used a switching regulator for up the efficiency, but it put a 1 kHz spur on the oscillator. The 10811 used two transistors on opposite sides to try to sort of distribute the heat. On the E1938A, we looked at an array of small surface mount transistors to have the best of both worlds. However, this turned out not to be manufacturable and we settled for resistive heaters (back to 1970!). Rick Karlquist N6RK Bruce Griffiths wrote: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Neville Michie wrote: If you use a transistor as a heater, the full supply voltage is across the element all the time, so heating is proportional to the current flowing. Neville Neville However using a transistor has the disadvantage of a small area heat source rather than the large area heat source possible with a heater winding. Using a small area heat source produces significant temperature gradients. 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. ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Rick Karlquist N6RK wrote: If you want to soup up at 10811 oven, externally wire in a larger capacitor in parallel and change the resistors to increase the gain. The 10811 designers did the best they could with what they had to work with, but you don't want to blindly copy them in new applications. That would be an interesting experiment. Hmmm ... I suppose we can presume that the 10811 tempco wasn't good enough for the requirements for the Z3801A, given that in that application the 10811 was placed inside of another oven. I now have both a Z3801A and a Z3815A w/E1938A. But I haven't yet compared them head to head. Tom: I presume the Z3801A is included in your GPSDO comparison project. Is the Z3815A included, too? What's your status? -ch ___ 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] Improving the stability of crystal oscillators
From: Bruce Griffiths [EMAIL PROTECTED] Subject: Re: [time-nuts] Improving the stability of crystal oscillators Date: Fri, 12 Oct 2007 10:08:34 +1300 Message-ID: [EMAIL PROTECTED] Hej Bruce and Neville, Neville Michie wrote: If you use a transistor as a heater, the full supply voltage is across the element all the time, so heating is proportional to the current flowing. Neville Neville However using a transistor has the disadvantage of a small area heat source rather than the large area heat source possible with a heater winding. Using a small area heat source produces significant temperature gradients. Using a single transistor yes. Spread out transistors can provide significantly less gradients. Cheers, Magnus ___ 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] Improving the stability of crystal oscillators
In a message dated 10/11/2007 14:31:04 Pacific Daylight Time, [EMAIL PROTECTED] writes: The lack of radiation shields and an isothermal block enclosing the oscillator components within the vacuum will surely reduce the performance somewhat. Bruce Hi Bruce, yes I would agree, the spec of 2E-07 is not that great by itself. But if we look at their market which seems to be space/military/Telecom mostly for this part, then it starts to make sense. Not many DIP size OCXO's out there, Micro Crystal makes one as well. I wonder how expensive these parts will be. If they are in the $30 to $75 range they could be a good match for a lot of apps. Nice building blocks nonetheless, and their phase noise is very acceptable for the size as well. No ADEV specs unfortunately. bye, Said ** See what's new at http://www.aol.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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY In a message dated 10/11/2007 11:52:37 Pacific Daylight Time, [EMAIL PROTECTED] writes: Maybe Vectron has figured out something we didn't think of or has sufficiently difference constraints that a vacuum makes sense for them. Rick Karlquist N6RK Hi Rick, they get 0.2ppm with it over -45C to 85C, I think that's a pretty acceptable performance in a small DIP-8 can which is not much bigger than a penny really, including all the circuitry! Probably the best insulator to use in that small of a case, where you only have a millimeter or two between the crystal blank and the housing. Any other material would probably have much less insulation. One interesting fact to mention is the +85C upper limit, there are very few OCXO's out there that run their crystals over 90C as would be required. Most seem to run between 80C and 90C and it get's really expensive if one looks for an OCXO that is speced to operate above +75C. Then again the DIP-8 is still vapor-ware... bye, Said ** See what's new at http://www.aol.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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi Tom: That's a cleaver improvement to a non ovenized crystal. Usually crystals are ground to have a temp vs freq turnover point occur at a specified temperature. The common one is to be on frequency at room temperature. So if a room temperature crystal is heated it's no longer operating at the turnover temperature and so there is a steep delta frequency vs. temperature slope. Did you get a crystal cut for your heater temperature or somehow match the heaters temperature to a turnover point on your crystal? I spent many many hours adjusting the oven temperature of a Gibbs frequency standard to get it right on the turnover point. Since the improvement in frequency stability depends on minimizing the temperature excursions it's good to have as much gain as possible in the heater feedback circuitry. This was done for the HP E1938 10 MHz oscillator, see: http://www.prc68.com/I/HPE1938.shtml and the paper: The Theory Of Zero Gradient Crystal Ovens, R.K. Karlquist, L.S. Cutler, E.M. Ingman, J.L. Johnson, T. Parisek Have Fun, Brooke Clarke, N6GCE http://www.PRC68.com http://www.precisionclock.com http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam Tom Clifton wrote: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY While the website is not explicitly about frequency measurement, there is an interesting bit on improving the stability of crystal oscillators with external heater controllers. While it may not be suitable for long term high stability control it might be suitable for many other purposes. http://www.qrss.thersgb.net/Crystal-Ovens.html The main page is also a good read: http://www.qrss.thersgb.net/Receiving-QRSS.html#Introduction Need a vacation? Get great deals to amazing places on Yahoo! Travel. http://travel.yahoo.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. ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY This is getting off topic (because it's far to practical!) but hanging heaters on crystals is a time-honored activity for hams. Many of the surplus FM rigs for VHF and UHF that we obtained from the likes of Motorola, GE, RCA, etc. that were made B.S. (before synthesizers) had ovens, or later channel elements that were actually TCXOs. This was particularly necessary for UHF systems that operated in rugged environments. But most ham-grade gear didn't have anything like this. I spent quite a bit of time 15 years ago building a packet radio network that linked Columbus, Dayton, and Cincinnati Ohio using UHF (440 MHz) 19.2 kbps data radios made by Kantronics, a company with limited RF experience. The data transmission scheme we used required a frequency tolerance of about +/- 2 kHz at 440 MHz (i.e., about 5x10e-6). The standard crystals could almost maintain that tolerance in a nicely regulated room, but we had these radios out in transmitter shacks in the middle of corn fields, and with wide temperature swings the radio links would die completely. We first built a small proportional heater circuit that we could shove in next to the crystal, and that worked OK. We finally found a source for thermistors spot welded to a spring clip that would mount snugly directly to the crystal case. With 12 volts applied, these heated the crystals very nicely. With the heaters, we were able to keep the systems running year round with about 1/10 the service calls. The original crystals (designed for room temperature) worked OK and we could warp them onto frequency even with the heaters installed, but we noticed what seemed to be accelerated aging; after a couple of years, the crystals could no longer be brought onto frequency. Later, we ordered some crystals designed for higher temperature (I think it was something like 50 degrees C) and those were both easier to trim, and didn't seem to suffer the rapid aging. That network is now dead and gone, victim of single-source components (Kantronics stopped making or supporting the radios, and some of the transistors became Unobtanium) as well as the death of traditional packet radio in the face of the internet. Sigh... John Brooke Clarke said the following on 10/10/2007 01:52 PM: Hi Tom: That's a cleaver improvement to a non ovenized crystal. Usually crystals are ground to have a temp vs freq turnover point occur at a specified temperature. The common one is to be on frequency at room temperature. So if a room temperature crystal is heated it's no longer operating at the turnover temperature and so there is a steep delta frequency vs. temperature slope. Did you get a crystal cut for your heater temperature or somehow match the heaters temperature to a turnover point on your crystal? I spent many many hours adjusting the oven temperature of a Gibbs frequency standard to get it right on the turnover point. Since the improvement in frequency stability depends on minimizing the temperature excursions it's good to have as much gain as possible in the heater feedback circuitry. This was done for the HP E1938 10 MHz oscillator, see: http://www.prc68.com/I/HPE1938.shtml and the paper: The Theory Of Zero Gradient Crystal Ovens, R.K. Karlquist, L.S. Cutler, E.M. Ingman, J.L. Johnson, T. Parisek Have Fun, Brooke Clarke, N6GCE http://www.PRC68.com http://www.precisionclock.com http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam Tom Clifton wrote: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY While the website is not explicitly about frequency measurement, there is an interesting bit on improving the stability of crystal oscillators with external heater controllers. While it may not be suitable for long term high stability control it might be suitable for many other purposes. http://www.qrss.thersgb.net/Crystal-Ovens.html The main page is also a good read: http://www.qrss.thersgb.net/Receiving-QRSS.html#Introduction ___ 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] Improving the stability of crystal oscillators
In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, [EMAIL PROTECTED] writes: We first built a small proportional heater circuit that we could shove in next to the crystal, and that worked OK. We finally found a source for thermistors spot welded to a spring clip that would mount snugly directly to the crystal case. With 12 volts applied, these heated the crystals very nicely. With the heaters, we were able to keep the systems running year round with about 1/10 the service calls. Hi John, interesting anecdote! Would you know if the thermistors are still available? Who made them? Thanks Said ** See what's new at http://www.aol.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] Improving the stability of crystal oscillators
[EMAIL PROTECTED] said the following on 10/10/2007 02:17 PM: In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, [EMAIL PROTECTED] writes: We first built a small proportional heater circuit that we could shove in next to the crystal, and that worked OK. We finally found a source for thermistors spot welded to a spring clip that would mount snugly directly to the crystal case. With 12 volts applied, these heated the crystals very nicely. With the heaters, we were able to keep the systems running year round with about 1/10 the service calls. Hi John, interesting anecdote! Would you know if the thermistors are still available? Who made them? We bought them as a replacement part from Yaesu USA. This data is 10 years or more old, but here you go: Part Name Yaesu Part Number Murata Part Number PosistorG9090019PTH507A01BG330N020 They used to be about $7.00 each. Yaesu's parts-order phone number at the time was (800) 255-9237. I'm not sure if there's another source for the Murata part; back then, we couldn't find one. Amazingly, I still have a web page documenting all that we learned about those cursed radios, including the schematic of our original homebrew heater design: http://www.febo.com/hamdocs/d4art.html. The quality of the heater schematic isn't very good, but it's all I have. John ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY [EMAIL PROTECTED] said the following on 10/10/2007 02:39 PM: BTW: I wonder how much effect thermistor and resistor-bridge aging as well as opamp offset drift has on the long term aging of typical OCXO's since it will shift the temperature setpoint of the crystal. I think this is an issue that's not receiving a lot of attention in the literature.. More anecdotes. I have a bunch of old Sulzer 2.5 and 5 oscillators. As Tom will happily tell you, one of these guys that still works well can be one of the best pieces of quartz you'll ever find (and a great toilet flush detector!). But most of mine are a bit flaky, and the thermistors seem to be the main problem. Each unit has at least two -- one is inside the inner oven and is part of a bridge that drives the TEMP meter position; it's supposed to read 0 when the oven is at temperature. Another is part of the bridge that sets the oven temperature; there are hand-chosen components designed to work with the thermistor to drive the heater to the right temperature. I've seen units where one or both was so far off, you couldn't really tell what the oven was doing. In at least one case, there was an open that drove the oven full blast continuously. Someday I'd like to build a test fixture that would allow measuring the crystal turning point and setting the ovens back to optimal temperature... So, aging of these parts can certainly be an issue. John ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY In a message dated 10/10/2007 11:34:43 Pacific Daylight Time, [EMAIL PROTECTED] writes: heater design: http://www.febo.com/hamdocs/d4art.html. The quality of the heater schematic isn't very good, but it's all I have. John Thanks John! BTW: I wonder how much effect thermistor and resistor-bridge aging as well as opamp offset drift has on the long term aging of typical OCXO's since it will shift the temperature setpoint of the crystal. I think this is an issue that's not receiving a lot of attention in the literature.. Said ** See what's new at http://www.aol.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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Try DigiKey pn: 235-1123-ND for a simple PTC Thermistor that can be soldered to the xtal case if one were so inclined. Do so at your own risk to the xtal! -Brian -- Original message -- From: John Ackermann N8UR [EMAIL PROTECTED] [EMAIL PROTECTED] said the following on 10/10/2007 02:17 PM: In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, [EMAIL PROTECTED] writes: We first built a small proportional heater circuit that we could shove in next to the crystal, and that worked OK. We finally found a source for thermistors spot welded to a spring clip that would mount snugly directly to the crystal case. With 12 volts applied, these heated the crystals very nicely. With the heaters, we were able to keep the systems running year round with about 1/10 the service calls. Hi John, interesting anecdote! Would you know if the thermistors are still available? Who made them? We bought them as a replacement part from Yaesu USA. This data is 10 years or more old, but here you go: Part Name Yaesu Part Number Murata Part Number Posistor G9090019PTH507A01BG330N020 They used to be about $7.00 each. Yaesu's parts-order phone number at the time was (800) 255-9237. I'm not sure if there's another source for the Murata part; back then, we couldn't find one. Amazingly, I still have a web page documenting all that we learned about those cursed radios, including the schematic of our original homebrew heater design: http://www.febo.com/hamdocs/d4art.html. The quality of the heater schematic isn't very good, but it's all I have. John ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY In a message dated 10/10/2007 19:34:55 GMT Daylight Time, [EMAIL PROTECTED] writes: We bought them as a replacement part from Yaesu USA. This data is 10 years or more old, but here you go: Part NameYaesu Part NumberMurata Part Number Posistor G9090019PTH507A01BG330N020 - I don't know if this is the same part, Ebay Ref...110177471348, but this seller has been selling these two at a time for quite a while. Might be ok if you just want a couple to play with, probably not ideal for planning a production run:-) regards Nigel GM8PZR ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi Brian: I used to use Balco (as far as I can remember) positive coefficient resistors that had specs similar to the Digikey units you linked to. These were only available in values under 200 Ohms and have a positive linear coefficient. The more common negative coefficient type like: http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1storeId=10001catalogId=10001productId=207036 have a much larger change with temperature and so are a very common way to sense a set point. When a resistor with the same value is used to make a half bridge the voltage change around the balance point is nearly linear. There's a way to fit a third order polynomial to the data and once you have the coefficients it's only a linear equation to solve for converting resistance back to temperature. Have Fun, Brooke Clarke http://www.PRC68.com http://www.precisionclock.com http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam [EMAIL PROTECTED] wrote: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Try DigiKey pn: 235-1123-ND for a simple PTC Thermistor that can be soldered to the xtal case if one were so inclined. Do so at your own risk to the xtal! -Brian -- Original message -- From: John Ackermann N8UR [EMAIL PROTECTED] [EMAIL PROTECTED] said the following on 10/10/2007 02:17 PM: In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, [EMAIL PROTECTED] writes: We first built a small proportional heater circuit that we could shove in next to the crystal, and that worked OK. We finally found a source for thermistors spot welded to a spring clip that would mount snugly directly to the crystal case. With 12 volts applied, these heated the crystals very nicely. With the heaters, we were able to keep the systems running year round with about 1/10 the service calls. Hi John, interesting anecdote! Would you know if the thermistors are still available? Who made them? We bought them as a replacement part from Yaesu USA. This data is 10 years or more old, but here you go: Part Name Yaesu Part Number Murata Part Number Posistor G9090019PTH507A01BG330N020 They used to be about $7.00 each. Yaesu's parts-order phone number at the time was (800) 255-9237. I'm not sure if there's another source for the Murata part; back then, we couldn't find one. Amazingly, I still have a web page documenting all that we learned about those cursed radios, including the schematic of our original homebrew heater design: http://www.febo.com/hamdocs/d4art.html. The quality of the heater schematic isn't very good, but it's all I have. John ___ 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] Improving the stability of crystal oscillators
From: [EMAIL PROTECTED] Subject: Re: [time-nuts] Improving the stability of crystal oscillators Date: Wed, 10 Oct 2007 14:17:24 EDT Message-ID: [EMAIL PROTECTED] John, In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, [EMAIL PROTECTED] writes: We first built a small proportional heater circuit that we could shove in next to the crystal, and that worked OK. We finally found a source for thermistors spot welded to a spring clip that would mount snugly directly to the crystal case. With 12 volts applied, these heated the crystals very nicely. With the heaters, we were able to keep the systems running year round with about 1/10 the service calls. Hi John, interesting anecdote! Agree! Thanks! Cheers, Magnus ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I bought 10kohm nominal NTC thermistors from Digikey, P/N 490-4653-ND. They are very small, 1/10th of an inch long or so. I have used those (or similar parts) in projects both at home and at work (in military equipment...) for about 15 years. Didier KO4BB -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Wednesday, October 10, 2007 1:17 PM To: time-nuts@febo.com Subject: Re: [time-nuts] Improving the stability of crystal oscillators In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, [EMAIL PROTECTED] writes: We first built a small proportional heater circuit that we could shove in next to the crystal, and that worked OK. We finally found a source for thermistors spot welded to a spring clip that would mount snugly directly to the crystal case. With 12 volts applied, these heated the crystals very nicely. With the heaters, we were able to keep the systems running year round with about 1/10 the service calls. Hi John, interesting anecdote! Would you know if the thermistors are still available? Who made them? Thanks Said ** See what's new at http://www.aol.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. ___ 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] Improving the stability of crystal oscillators
I have made several ovens for oscillators over the years. The recipe is: get a piece of aluminium big enough to contain the oscillator, voltage regulator and first stage amplifier. With a mill remove the shapes of each component. Bolt a large power transistor, large power fets are best, to the outside of the block as a heater, and it is run off the unregulated input power. Judicious selection of a component decides the start-up current. Make a plate to cover the excavation for the components, and bolt it down. The circuit can be made with discrete transistors in the most unstable looking amplifier ever seen, alternating NPN and PNP transistors, connected directly to each other with load resistors. The main temperature sensor is a resistor bridge with a high value glass encapsulated thermistor. These are available a several trade houses. The amplifier is also temperature sensitive, but is within the thermal loop. The thermistor bridge gives a very large signal ~ 50mV per degree. Gain may have to be backed off if thermal oscillations do not die down, but the metal block acts as an integrator and the circuits are very easy to get high gain and sensitivity. The whole block is packed in two inches of foam insulation, my 1MHz oscillator only draws about 80 mA at 12 volts. The temperature is set to 40 C. The stability of the oscillator is very good, but as I have not yet got a disciplined oscillator going I dont know which is drifting, the HP 10811 in my frequency counter or the 1MHz oscillator. After a year, the difference is currently 0.3 ppm. cheers Neville Michie On 11/10/2007, at 9:24 AM, Didier Juges wrote: I bought 10kohm nominal NTC thermistors from Digikey, P/N 490-4653- ND. They are very small, 1/10th of an inch long or so. I have used those (or similar parts) in projects both at home and at work (in military equipment...) for about 15 years. Didier KO4BB -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Wednesday, October 10, 2007 1:17 PM To: time-nuts@febo.com Subject: Re: [time-nuts] Improving the stability of crystal oscillators In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, [EMAIL PROTECTED] writes: We first built a small proportional heater circuit that we could shove in next to the crystal, and that worked OK. We finally found a source for thermistors spot welded to a spring clip that would mount snugly directly to the crystal case. With 12 volts applied, these heated the crystals very nicely. With the heaters, we were able to keep the systems running year round with about 1/10 the service calls. Hi John, interesting anecdote! Would you know if the thermistors are still available? Who made them? Thanks Said ** See what's new at http://www.aol.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. ___ 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] Improving the stability of crystal oscillators
Neville Michie wrote: I have made several ovens for oscillators over the years. The recipe is: get a piece of aluminium big enough to contain the oscillator, voltage regulator and first stage amplifier. With a mill remove the shapes of each component. Bolt a large power transistor, large power fets are best, to the outside of the block as a heater, and it is run off the unregulated input power. Judicious selection of a component decides the start-up current. Make a plate to cover the excavation for the components, and bolt it down. The circuit can be made with discrete transistors in the most unstable looking amplifier ever seen, alternating NPN and PNP transistors, connected directly to each other with load resistors. The main temperature sensor is a resistor bridge with a high value glass encapsulated thermistor. These are available a several trade houses. The amplifier is also temperature sensitive, but is within the thermal loop. The thermistor bridge gives a very large signal ~ 50mV per degree. Gain may have to be backed off if thermal oscillations do not die down, but the metal block acts as an integrator and the circuits are very easy to get high gain and sensitivity. The whole block is packed in two inches of foam insulation, my 1MHz oscillator only draws about 80 mA at 12 volts. The temperature is set to 40 C. The stability of the oscillator is very good, but as I have not yet got a disciplined oscillator going I dont know which is drifting, the HP 10811 in my frequency counter or the 1MHz oscillator. After a year, the difference is currently 0.3 ppm. cheers Neville Michie Neville A correctly tuned PID control loop should allow even tighter temperature control. A boostrapped oven like that used by Wenzel should be even better. (http://www.wenzel.com/documents/Sub-pico%20Multiplier.pdf). Despite Wenzel's claims this type of oven isn't new it was used for portable standard cell enclosures decades ago. 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.
