Re: [time-nuts] Thunderbolt stability and ambient temperature
Bruce Griffiths wrote: Rex wrote: Now, back to the subject of heat, I have a strange observation that I posted on the web a few years ago. A few people thought they had seen the same thing, but most thought what I noticed was not real. I posted because, if it was true, it seemed unexpected and I had never heard anything that could explain it. I was welding or heat treating steel. Imagine a steel bar about 1 inch (2.54 cm) in diameter and a foot to 18 (30-40 cm) long. The bar is clamped in a vise and with a torch one end is quickly brought up to red heat. The other end is still cool enough that with my bare hand I can hold the bar by the cool end and carry it into the next room. I carry it there to cool it in the sink. A stream of cold water turned on, I quickly cool the hot end in the water. My observation, from doing this several times, is that the cold water quickly absorbes heat from the red end, but also seems to chase a lot of the heat quickly up toward the cold end, making the bar rapidly uncomfortable to hold. So that's my observation. I think the sudden cooling of the very hot end has somehow chased a glob of heat toward the cool end. If true, I have no explanation. I don't think it is related to steam; it seems to me to be something happening inside the bar. Most people thought it was coincidence of heat propagating up the bar just at that time, or steam. Could be, but I still think it is real. The cold end of the bar was slowly getting warmer as I carried it, but after the sudden cooling of the hot end, the cold end seemed to get hot fast. I meant to try an experiment with two bars and dual thermocouples, but I never got around to it. The main problem is getting things close enough to compare without questioning the heated states. My plan would have been: attach two themocouples to the cold end of two identical bars. Heat the two other ends rapidly to red heat (that is the very hard part to get right and balanced) and then just cool one bar rapidly while recording both temp profiles of the cold ends. If I figure out how to do the heating quick and balanced, I may still try the experiment. So I started with a bit of complaining about the rambling of the thread, and now I've rambled it in a whole nother direction. Sorry, I guess. Rex your experience with the hot bar is quite common. Bruce Bruce, Good to hear someone with your credentials validate my heat-chasing observation. I am not aware of anything in common physics that explains the phenomina. Is there some kind of thermodynamic or atomic explanation? Got any leads? -Rex ___ 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] Thunderbolt stability and ambient temperature
Rex your experience with the hot bar is quite common. Sounds like a pretty reasonable manifestation of the Leidenfrost effect. The water in contact with the hot end of the bar vaporizes, and the resulting steam layer (which might be microscopic) does a good job insulating the bar. There's nowhere else for the heat to radiate or conduct to, except towards the cold end of the bar. -- 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] Thunderbolt stability and ambient temperature
2009/6/11 Chuck Harris cfhar...@erols.com: Joseph M Gwinn wrote: ... Yes, but water is so much easier to find, and easier to package, plus it has a great storage capability. And evaporates and leaks. But yes, I've used water for quick jobs. I just don't know what to say to that! Even a child can put a case of bottled water in a box, and not have it evaporate or leak. I would venture that said case of bottled water will still be full up when the child graduates from college, and has kids of his own. But goodness knows what sort of a biological hazard it will be by then :-) -Chuck Harris ___ 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. -- Steve Rooke - ZL3TUV G8KVD JAKDTTNW A man with one clock knows what time it is; A man with two clocks is never quite sure. ___ 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] Thunderbolt stability and ambient temperature
Rex skrev: Now, back to the subject of heat, I have a strange observation that I posted on the web a few years ago. A few people thought they had seen the same thing, but most thought what I noticed was not real. I posted because, if it was true, it seemed unexpected and I had never heard anything that could explain it. I was welding or heat treating steel. Imagine a steel bar about 1 inch (2.54 cm) in diameter and a foot to 18 (30-40 cm) long. The bar is clamped in a vise and with a torch one end is quickly brought up to red heat. The other end is still cool enough that with my bare hand I can hold the bar by the cool end and carry it into the next room. I carry it there to cool it in the sink. A stream of cold water turned on, I quickly cool the hot end in the water. My observation, from doing this several times, is that the cold water quickly absorbes heat from the red end, but also seems to chase a lot of the heat quickly up toward the cold end, making the bar rapidly uncomfortable to hold. So that's my observation. I think the sudden cooling of the very hot end has somehow chased a glob of heat toward the cool end. If true, I have no explanation. I don't think it is related to steam; it seems to me to be something happening inside the bar. The propagation speed for the heat comes into play. It takes time for the heat from the hot end to reach the cold end. As we are fairly off track here, let me relay a similar story. My mother has been working with food all her professional life. A christmas tradition here in Sweden is to have big lumps of ham from which you carve slices. However, the damn thing needs to be cooked. If you do it in the oven it dries out, if you only boil it you do not get that crisp surface people want. You can do a bit of both. However, one year she thought about cooking it in the microwave oven. She has no formal training in thermodynamics and didn't really involve me in the thought process, but she figured that if she ran the microwave for half an hour, after wrapping the ham in microwave-grade plastic, just to avoid it to dry out, and then just let it sit on the bench, then it would hit those 70 degrees in the core after a while anyway. Sure thing, it did. Worked like a charm. Perfectly cooked, juicy. What happends is that it takes time for the heat-wave to reach the core, so even if she stopped providing more heat the heat-wave was still in progress and just could not be stopped. Most people thought it was coincidence of heat propagating up the bar just at that time, or steam. Could be, but I still think it is real. The cold end of the bar was slowly getting warmer as I carried it, but after the sudden cooling of the hot end, the cold end seemed to get hot fast. Yes... it would have got hot regardless of cooling or not at the hot end. Also, the heat-wave wavefront isn't a flat surface... I meant to try an experiment with two bars and dual thermocouples, but I never got around to it. The main problem is getting things close enough to compare without questioning the heated states. My plan would have been: attach two themocouples to the cold end of two identical bars. Heat the two other ends rapidly to red heat (that is the very hard part to get right and balanced) and then just cool one bar rapidly while recording both temp profiles of the cold ends. If I figure out how to do the heating quick and balanced, I may still try the experiment. That would be a neat exercise to demonstrate things... So I started with a bit of complaining about the rambling of the thread, and now I've rambled it in a whole nother direction. Sorry, I guess. I guess it is an interesting side topic, the food aside. 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] Thunderbolt stability and ambient temperature
In message 4a30457e.9060...@erols.com, Chuck Harris writes: And evaporates and leaks. But yes, I've used water for quick jobs. I just don't know what to say to that! Even a child can put a case of bottled water in a box, and not have it evaporate or leak. I would venture that said case of bottled water will still be full up when the child graduates from college, and has kids of his own. Unless UPS or DHL decides to leave your package stranded on a loading dock in -20°C for a couple of days. In the lab I *might* use water, for shipping I never would. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] Thunderbolt stability and ambient temperature
In message 4a309b30.7000...@sonic.net, Rex writes: My observation, from doing this several times, is that the cold water quickly absorbes heat from the red end, but also seems to chase a lot of the heat quickly up toward the cold end, making the bar rapidly uncomfortable to hold. I've seen the effect you describe explained in an article somewhere, very likely New Scientist or SciAm about five years ago. When you rapidly heat or cool metals, very often changes in crystal lattice structure is involved some of them resulting in quite drastic changes to volume. Heat is essentially atoms wiggling about, and when you change the modes of freedom for the atoms, they may have to wiggle harder. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] AD9548 - Clock IC Generates Up to 400 MHz from 1 PPSGPS Signal
However it does discipline the DDS outputs as intended. It is somewhat akin to Ulrich's approach perhaps without the robust outlier rejection. Surely AD has not copied from me, but yes indeed this looks similar to my approach. The output noise may by tamed by loosely coupling a high quality OCXO to the output. Perhaps one should think over a circuit that a) surpresses PPS outliers and b) applies sawtooth correction to the PPS Best regads Ulrich Bangert -Ursprüngliche Nachricht- Von: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] Im Auftrag von Bruce Griffiths Gesendet: Donnerstag, 11. Juni 2009 07:42 An: les...@veenstras.com; Discussion of precise time and frequency measurement Betreff: Re: [time-nuts] AD9548 - Clock IC Generates Up to 400 MHz from 1 PPSGPS Signal However it does discipline the DDS outputs as intended. It is somewhat akin to Ulrich's approach perhaps without the robust outlier rejection. This approach would allow a wide range of relatively stable low noise sources to be used including those that may have drifted out of adjustment range. One drawback for some applications is the relatively high phase noise floor. Bruce Lester Veenstra wrote: Sync to 1 pps but will not discipline the frequency source Lester B Veenstra MØYCM K1YCM les...@veenstras.com m0...@veenstras.com k1...@veenstras.com US Postal Address: PSC 45 Box 781 APO AE 09468 USA UK Postal Address: Dawn Cottage Norwood, Harrogate HG3 1SD, UK Telephones: Office: +44-(0)1423-846-385 Home: +44-(0)1943-880-963 Guam Cell: +1-671-788-5654 UK Cell: +44-(0)7716-298-224 US Cell: +1-240-425-7335 Jamaica: +1-876-352-7504 This e-mail and any documents attached hereto contain confidential or privileged information. The information is intended to be for use only by the individual or entity to whom they are addressed. If you are not the intended recipient or the person responsible for delivering the e-mail to the intended recipient, be aware that any disclosure, copying, distribution or use of the contents of this e-mail or any documents attached hereto is prohibited. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of christopher hoover Sent: Thursday, June 11, 2009 5:26 AM To: time-nuts@febo.com Subject: [time-nuts] AD9548 - Clock IC Generates Up to 400 MHz from 1 PPSGPS Signal [fyi -- this may be of general interest, but n.b. that this A.D. marketing - ch] Clock IC Generates Up to 400 MHz from 1 PPS GPS Signal The AD9548 http://www.analog.com/en/clock-and-timing/clock-generation-an d-distribution /ad9548/products/product.html is the first clock chip in the industry to directly generate up to a 400 MHz output clock, with extremely low phase noise, that is locked to a standard one pulse-per-second (PPS) GPS clock signal. This performance is a result of combining Analog Devices' proprietary direct digital synthesis (DDS) technology with a state-of-the-art digital phase-locked loop (DPLL). Other solutions for synchronizing to the GPS 1 PPS source typically rely on one or more frequency upconversion steps. Maintaining low output noise, while providing over eight orders of magnitude of frequency scaling (1 Hz input to over 100 MHz output), is a significant challenge. The AD9548 is able to mitigate this effect thanks to a digital loop filter capable of bandwidths as low as 1 MHz (10 Hz to 3 Hz). / / ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Thunderbolt stability and ambient temperature
John Miles wrote: Rex your experience with the hot bar is quite common. Sounds like a pretty reasonable manifestation of the Leidenfrost effect. The water in contact with the hot end of the bar vaporizes, and the resulting steam layer (which might be microscopic) does a good job insulating the bar. There's nowhere else for the heat to radiate or conduct to, except towards the cold end of the bar. -- john, KE5FX John, You too never cease to impress by providing bits of knowledege I've never heard about. Leidenfrost effect. My first instinct was to dismember the German word, which was a bad idea. Wiki told me about the relevant meaning. Yes, that is a possibility about what I may have observed. Let's see. I should produce the same efffect by jamming the hot end into a tight insulating hole. Shouldn't be too hard to test subjectively. My guess -- there is more than that involved. But just speculation so far. I haven't even proved my initial observation. ___ 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] Thunderbolt stability and ambient temperature
Poul-Henning Kamp wrote: In message 4a309b30.7000...@sonic.net, Rex writes: My observation, from doing this several times, is that the cold water quickly absorbes heat from the red end, but also seems to chase a lot of the heat quickly up toward the cold end, making the bar rapidly uncomfortable to hold. I've seen the effect you describe explained in an article somewhere, very likely New Scientist or SciAm about five years ago. When you rapidly heat or cool metals, very often changes in crystal lattice structure is involved some of them resulting in quite drastic changes to volume. Heat is essentially atoms wiggling about, and when you change the modes of freedom for the atoms, they may have to wiggle harder. Thanks, that sounds like the most likely explanation I have heard. If you find a more complete citation, I'd be interested to hear about it. ___ 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] Thunderbolt stability and ambient temperature
For PLL steered devices, you want your device enclosed by a thermal mass which is again enclosed by a layer of thermal isolation. The goal is to filter/average all rapid (daily ?) external temperature influences, only letting through such slow variations (seasonal ?) which the PLL can comfortably cope with. My impression with this thread is that two sligthly different things are being discussed here: Some posters explain how a crystal oven shall be designed as Poul-Henning does with his words above. Absolute correct, no doubt about it! Nevertheless only a VERY few of us (Rick for example) have real experience in designing ovens and most of us are confronted with a existent ready to go OCXOs. That is why one can start a discussion about the question whether the thermal properties of an existing OCXO can be improved which is what the second group of posters has done starting with the Thunderbolt. The situation with the ready to go OCXO is a bit different than starting from scratch: The OCXO DOES already have a certain thermal mass inside and it DOES already have a certain thermal insulation of this mass against the ambient. BOTH of these parameters have been important properties for the designer of the oven's temperature controller. The temperature controller's properties must match EXACTLY the thermal mass as well as the amount of insulation in order to work as expected. If one of you has personal experience with high precision temperature controllers I am sure he can second this claim. The situation gets the harder the better the thermal insulation is: You need to avoid every kind of regulation overshot because it is only the high insulation that allows energy to leak out of the thermal mass. Which in turn requires high regulator time constants. By the way: That is also the reason for the heat sinks on rubidium standards. They form a good coupling to the ambient (=small insulation) making the design of the lamp's temperature controller much more easy and much faster than with a good insulation. With a ready OCXO in your hand like the 10811 or the FTS1200 or anything else: You can't improve the beast by simply better insulation or by simply higher thermal mass, because every change in this will have worse impacts on the action of the temperature controller. However, there ARE ways to improve the thermal behavour of an ready to go OCXO: First rule: Allow the temperature controller to see the original thermal mass, i.e. don't open the enclosure and don't change anything, just leave everything as it is. Second rule: Allow the temperature controller to see the original thermal insulation, i.e. allow for some cubic centimeters of air around the OCXO's outer enclosure. It was engineered with that surrounding in mind! Third rule: Outside of the these few cubic centimeters of air around the OCXO you are allowed ANYTHING. You can for example put a big thermal mass like a massive aluminium enclosure around the OCXO (but please don't forget the few cubic centimeters of air between this and the surface of the OCXO). THIS thermal mass in conjunction with the air around it will work as the thermal lowpass filter that some posters talked about but WITHOUT worrying the OCXO's temperature controller because it sees the original thermal mass and the original thermal insulation. But it sees smaller ambient temperature variations than before. This would be a passive solution where the aim were to get high time constants for the combination of the outer enclosure and the surrounding air making as much thermal mass as possible the prefered way. One of my 10811 resides in a 12 X 12 X 12 cm aluminium enclosure with 2 cm wall thickness. This has given a thermal time constant in the order of precious few hours if i remember correctly and was far from averaging daily temperature changes. It might however be helpful for the discussed problem of Thunderbolt reactions to short time temperature changes. Or one can decide for a active solution. This would call for an outer enclosure where not high thermal mass but high thermal conductivity were the aim which is brought to a constant temperature by means of a second temperature controller, the famous double oven principle if you like. As in the passive case there must be enough air between OCXO and the outer controller in order to avoid any interaction between the temperature controllers. Best regards Ulrich Bangert -Ursprungliche Nachricht- Von: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] Im Auftrag von Poul-Henning Kamp Gesendet: Donnerstag, 11. Juni 2009 00:43 An: Discussion of precise time and frequency measurement Betreff: Re: [time-nuts] Thunderbolt stability and ambient temperature In message 4a3033fc.6070...@xtra.co.nz, Bruce Griffiths writes: Hal Murray wrote: Thermal wave reflection at boundaries/interfaces does occur: If your frequency or voltage standard is in a physical environment where these
Re: [time-nuts] Thunderbolt stability and ambient temperature
In message e182724b9fce4b9f9e914bcc4f374...@athlon, Ulrich Bangert writes: For PLL steered devices, you want your device enclosed by a thermal mass which is again enclosed by a layer of thermal isolation. The goal is to filter/average all rapid (daily ?) external temperature influences, only letting through such slow variations (seasonal ?) which the PLL can comfortably cope with. My impression with this thread is that two sligthly different things are being discussed here: Some posters explain how a crystal oven shall be designed as Poul-Henning does with his words above. Absolute correct, no doubt about it! I'm not talking about crystal ovens, I'm talking about timekeeping kit in general: how to filter high frequency temperature fluctuations out, so the PLL does not have to deal with them. The above advice applies to GPSDO's and Rb's and Cs's as well as TCXOs, OCXOs and voltage references. Poul-Henning -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] Thunderbolt stability and ambient temperature
I'm not talking about crystal ovens, I'm talking about timekeeping kit in general: how to filter high frequency temperature fluctuations out, so the PLL does not have to deal with them. Ok, but in this general case you have to accept the fact, that filtering high temperature fluctuations is only ONE part of the engineering job. The second task (which I tried to point at) is: When you do already have a closed loop temperature regulation system inside what you plan to built around it, then you need to manage the filtering without mal interaction of the local temperature controller with your additional filtering stuff. The art is to make the closed temperature loop inside see only smaller temperature fluctuations but No changes otherwise. If you apply an overall change in temperature insulation to the ambient you will make the work of the inside temperature controller a lot harder because it is not prepared for that. In the aluminium box that i wrote about I have for an experiment replaced the air between the 10811 and the outer box with a material that has a significant lower temperature conductivity than standing air. You can easily watch the temperature controller go crazy with that. For a second experiment I have replaced the air with a material having lots more of thermal conductivity than air and you can watch the temperature controller go crazy with that too. You don't need sophisticated temperature measurement equipment to see the controller go crazy, just watch the frequency of the oscillator. This will tell you all about it. Things are different, if you have an influence on the controller's regulation parameters (which you do not have with a ready bought device). If you do have, then your additional provisions for filtering and insulation can easily be included into the thermal model that the temperature controller has to handle and will lead to different operation parameters of the controller. That will of course work and that is why I compared your suggestions to designing a new oven (for xtal or rubidium or whatever). Best regards Ulrich Bangert -Ursprungliche Nachricht- Von: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] Im Auftrag von Poul-Henning Kamp Gesendet: Donnerstag, 11. Juni 2009 12:50 An: Discussion of precise time and frequency measurement Betreff: Re: [time-nuts] Thunderbolt stability and ambient temperature In message e182724b9fce4b9f9e914bcc4f374...@athlon, Ulrich Bangert writes: For PLL steered devices, you want your device enclosed by a thermal mass which is again enclosed by a layer of thermal isolation. The goal is to filter/average all rapid (daily ?) external temperature influences, only letting through such slow variations (seasonal ?) which the PLL can comfortably cope with. My impression with this thread is that two sligthly different things are being discussed here: Some posters explain how a crystal oven shall be designed as Poul-Henning does with his words above. Absolute correct, no doubt about it! I'm not talking about crystal ovens, I'm talking about timekeeping kit in general: how to filter high frequency temperature fluctuations out, so the PLL does not have to deal with them. The above advice applies to GPSDO's and Rb's and Cs's as well as TCXOs, OCXOs and voltage references. Poul-Henning -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] Thunderbolt stability and ambient temperature
I didn't try it but if You want to average daily (or even seasonal) temperature changes, one could drill the floor of a cellar ( Your time-nuts gear is in the cellar, isn't it?) with the geotechnical drill used for core samples of soil and rock . 3-4 inch diameter drills are standard, and surely make enough space for 10811. Few meters down, I expect seasonal changes 1-2 deg with 50 deg external winter-summer change. Under buildings probably even less...(permafrost story...) Plastic sewage pipe inserted in to keep water out, and You have thermal mass as much as You like. P. Dukic At 12:46 11.6.2009, you wrote: For PLL steered devices, you want your device enclosed by a thermal mass which is again enclosed by a layer of thermal isolation. The goal is to filter/average all rapid (daily ?) external temperature influences, only letting through such slow variations (seasonal ?) which the PLL can comfortably cope with. My impression with this thread is that two sligthly different things are being discussed here: Some posters explain how a crystal oven shall be designed as Poul-Henning does with his words above. Absolute correct, no doubt about it! Nevertheless only a VERY few of us (Rick for example) have real experience in designing ovens and most of us are confronted with a existent ready to go OCXOs. That is why one can start a discussion about the question whether the thermal properties of an existing OCXO can be improved which is what the second group of posters has done starting with the Thunderbolt. The situation with the ready to go OCXO is a bit different than starting from scratch: The OCXO DOES already have a certain thermal mass inside and it DOES already have a certain thermal insulation of this mass against the ambient. BOTH of these parameters have been important properties for the designer of the oven's temperature controller. The temperature controller's properties must match EXACTLY the thermal mass as well as the amount of insulation in order to work as expected. If one of you has personal experience with high precision temperature controllers I am sure he can second this claim. The situation gets the harder the better the thermal insulation is: You need to avoid every kind of regulation overshot because it is only the high insulation that allows energy to leak out of the thermal mass. Which in turn requires high regulator time constants. By the way: That is also the reason for the heat sinks on rubidium standards. They form a good coupling to the ambient (=small insulation) making the design of the lamp's temperature controller much more easy and much faster than with a good insulation. With a ready OCXO in your hand like the 10811 or the FTS1200 or anything else: You can't improve the beast by simply better insulation or by simply higher thermal mass, because every change in this will have worse impacts on the action of the temperature controller. However, there ARE ways to improve the thermal behavour of an ready to go OCXO: First rule: Allow the temperature controller to see the original thermal mass, i.e. don't open the enclosure and don't change anything, just leave everything as it is. Second rule: Allow the temperature controller to see the original thermal insulation, i.e. allow for some cubic centimeters of air around the OCXO's outer enclosure. It was engineered with that surrounding in mind! Third rule: Outside of the these few cubic centimeters of air around the OCXO you are allowed ANYTHING. You can for example put a big thermal mass like a massive aluminium enclosure around the OCXO (but please don't forget the few cubic centimeters of air between this and the surface of the OCXO). THIS thermal mass in conjunction with the air around it will work as the thermal lowpass filter that some posters talked about but WITHOUT worrying the OCXO's temperature controller because it sees the original thermal mass and the original thermal insulation. But it sees smaller ambient temperature variations than before. This would be a passive solution where the aim were to get high time constants for the combination of the outer enclosure and the surrounding air making as much thermal mass as possible the prefered way. One of my 10811 resides in a 12 X 12 X 12 cm aluminium enclosure with 2 cm wall thickness. This has given a thermal time constant in the order of precious few hours if i remember correctly and was far from averaging daily temperature changes. It might however be helpful for the discussed problem of Thunderbolt reactions to short time temperature changes. Or one can decide for a active solution. This would call for an outer enclosure where not high thermal mass but high thermal conductivity were the aim which is brought to a constant temperature by means of a second temperature controller, the famous double oven principle if you like. As in the passive case there must be enough air between OCXO and the outer controller in
Re: [time-nuts] Thunderbolt stability and ambient temperature
Poul-Henning Kamp wrote: In message 4a30457e.9060...@erols.com, Chuck Harris writes: And evaporates and leaks. But yes, I've used water for quick jobs. I just don't know what to say to that! Even a child can put a case of bottled water in a box, and not have it evaporate or leak. I would venture that said case of bottled water will still be full up when the child graduates from college, and has kids of his own. Unless UPS or DHL decides to leave your package stranded on a loading dock in -20°C for a couple of days. In the lab I *might* use water, for shipping I never would. I thought we were talking about stabilizing the temperature environment around frequency/time standards? I recall the discussion talking of big hunks of aluminum, copper, cast-iron engine blocks bought at scrap yards, and other such unshippable things. The nice thing about using water as a thermal ballast is you don't have to ship it specially. It is available everywhere humans go. If you are worried about it freezing, a 50-50 mix with ethylene glycol will protect it from freezing down to -40C, or so, though if we are talking about temperatures like that, it is unlikely that your precision clock is going to work very well down there. -Chuck ___ 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] Thunderbolt stability and ambient temperature
Hey Bruce, Your answers seem somewhat 'mechanical'. Are you a 'bot? Not a joke... REAL question. -John == Rex wrote: Hal Murray wrote: p...@phk.freebsd.dk said: Can I get reflections without some inductance? Is there any inductance in a system of alternating layers of insulation/storage? I think you are overstretching the badly chosen nomenclatures parallels to electricity. It was actually a (somewhat?) serious question on several grounds. Can I get reflections from a lumped circuit model of a transmission line made out of just Rs and Cs? If so, I can probably do the same in the thermal world. Can I get reflections in a thermal context? Bruce's URLs say yes, but my math is rusty enough that I can't quickly understand what's going on. If a thermal problem can generate reflections, does that mean it also has something corresponding to inductance? If so, what is it? It's possible that the key idea is time-delay. In the electrical world, a delay is a transmission line which has both C and L. I'm not sure what the one-dimensional equivalent in the thermal world is. What's the speed-of-light equivalent in the thermal world? Why were you somewhat serious about this? If you want to extropolate heat into electromagnestic waves, what would be the analog of frequency? There are a few parallels in the two realms by analogy but that doesn't mean they map in all aspects. Sometimes, to help learning ohms law, the analogy of water is used with pressure = voltage, flow = current, resistance = narrow pipes. It sort of makes the concepts easier to grasp, but when you get to AC and wave reflections I think one has to struggle to make the water analogy useful. For heat, I think the water analog might be more useful than trying to map the EM waves to heat. The reflection idea did remind me of something that occurred to me, a gallows-humor joke from years back. I'm sure most of you remember hearing about the 1989 San Francisco earthquake. The earthquake epicenter was between Santa Cruz and San Jose, about 40 miles south of San Francisco, but a lot of the serious damage and fires occurred in San Francisco near the tip of the penninsula at the bay shore. There was a lot of discussion about this localized damage so far away, and how that could happen. San Francisco is at the tip of a peninsula that forms the Bay. I immediately thought that the problem was obvious. The penninsula was excited at its bottom end and was left improperly terminated at San Francisco. I couldn't tell this joke for two reasons, one: it was in bad taste, but two: I only knew a few people who would get it -- the mismatch/termination joke. Now, back to the subject of heat, I have a strange observation that I posted on the web a few years ago. A few people thought they had seen the same thing, but most thought what I noticed was not real. I posted because, if it was true, it seemed unexpected and I had never heard anything that could explain it. I was welding or heat treating steel. Imagine a steel bar about 1 inch (2.54 cm) in diameter and a foot to 18 (30-40 cm) long. The bar is clamped in a vise and with a torch one end is quickly brought up to red heat. The other end is still cool enough that with my bare hand I can hold the bar by the cool end and carry it into the next room. I carry it there to cool it in the sink. A stream of cold water turned on, I quickly cool the hot end in the water. My observation, from doing this several times, is that the cold water quickly absorbes heat from the red end, but also seems to chase a lot of the heat quickly up toward the cold end, making the bar rapidly uncomfortable to hold. So that's my observation. I think the sudden cooling of the very hot end has somehow chased a glob of heat toward the cool end. If true, I have no explanation. I don't think it is related to steam; it seems to me to be something happening inside the bar. Most people thought it was coincidence of heat propagating up the bar just at that time, or steam. Could be, but I still think it is real. The cold end of the bar was slowly getting warmer as I carried it, but after the sudden cooling of the hot end, the cold end seemed to get hot fast. I meant to try an experiment with two bars and dual thermocouples, but I never got around to it. The main problem is getting things close enough to compare without questioning the heated states. My plan would have been: attach two themocouples to the cold end of two identical bars. Heat the two other ends rapidly to red heat (that is the very hard part to get right and balanced) and then just cool one bar rapidly while recording both temp profiles of the cold ends. If I figure out how to do the heating quick and balanced, I may still try the experiment. So I started with a bit of complaining about the rambling of the thread, and now I've rambled it in a whole nother direction.
Re: [time-nuts] Thunderbolt stability and ambient temperature
This is an absolutely standard problem in an undergraduate Heat Transfer course. Look for heating or cooling a block of material and thermal diffusivity. Take a look at most any decent text (Rosenow(?) Choi, 'Heat, Mass, Momentom Transfer') for example) That said, the geometry of a ham makes a closed form solution more difficult, requiring numerical methods. -John As we are fairly off track here, let me relay a similar story. My mother has been working with food all her professional life. A christmas tradition here in Sweden is to have big lumps of ham from which you carve slices. However, the damn thing needs to be cooked. If you do it in the oven it dries out, if you only boil it you do not get that crisp surface people want. You can do a bit of both. However, one year she thought about cooking it in the microwave oven. She has no formal training in thermodynamics and didn't really involve me in the thought process, but she figured that if she ran the microwave for half an hour, after wrapping the ham in microwave-grade plastic, just to avoid it to dry out, and then just let it sit on the bench, then it would hit those 70 degrees in the core after a while anyway. Sure thing, it did. Worked like a charm. Perfectly cooked, juicy. What happends is that it takes time for the heat-wave to reach the core, so even if she stopped providing more heat the heat-wave was still in progress and just could not be stopped. ___ 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] Thunderbolt stability and ambient temperature
It has nothing to do with this. A long (length width) bar can simply be modeled as a long ladder of series resistors's and capacitors to ground: ---zzz---zzz---zzz ... ---zzz--- _|_ _|_ _|_ _|_ ___ ___ ___ ___ | |-|- ... |- If you put a rectangular pulse in the left end, it will emerge later and very much rounded at the right end. Either do the math or simulate it in Spice or with a handful of R's and C's and a pulse generator and scope. No inductors needed. PERIOD. That model fully accounts for your observations with the bar heated at one end. -John = In message 4a309b30.7000...@sonic.net, Rex writes: My observation, from doing this several times, is that the cold water quickly absorbes heat from the red end, but also seems to chase a lot of the heat quickly up toward the cold end, making the bar rapidly uncomfortable to hold. I've seen the effect you describe explained in an article somewhere, very likely New Scientist or SciAm about five years ago. When you rapidly heat or cool metals, very often changes in crystal lattice structure is involved some of them resulting in quite drastic changes to volume. Heat is essentially atoms wiggling about, and when you change the modes of freedom for the atoms, they may have to wiggle harder. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] Thunderbolt stability and ambient temperature
Ed, and the big group I did run such a 10811 without the outer heater connected and without any insulation around as replacement for the original insulation and box but I did not see any fluctuations beside the normal behaviour of a 10811. (I have to admit that I did not yet run precision records, neither for the heater current nor for the frequency output. I see what I have to do soon!) This model is obviously adjusted inside to work best in an encreased environment of around 40 to 45 deg. C . I think as Ulrich does explain, blocking the heat flow significantly must deteriorate the regulating loop parameters. The life time of the oscillator electronics outside the stabilized crystal element will as well decrease... A good idea in fact to put the standard in a stable area and very slow varying temp range of around 15 deg. C underneath the house fundaments...I will think about! Did anybody ever think to apply wood as stabilizing element around an oscillator? Wood behaves a bit strange, it is on one side a not bad insulator and it does have as well a quite high heat storage capacity! (Oak with around 2.4 J/g, K., Lambda 0.17 W/m.K,, Pine around 2.7 J/g.K., Lambda 0.14 W/m.K. Water around 4.18 J/g.K., Lambda 0,604 W/m.K. Copper has 0.385 2.4 J/g, K., Lambda 401 W/m.K. at 25 deg. C. ) I consider wood a very intersting material, cheap and easy to work... Arnold On Thu, 11 Jun 2009 09:22:00 -0600, Ed Palmer wrote: Ulrich, when you changed the thermal characteristics around your 10811, how 'crazy' did it become? According to your theory, there should be differences in the schematics of the oven controllers between the single and double oven variants of the 10811. Last year I picked up a couple of those double oven 10811s from China that had the outer insulation removed. I wonder if I could see any anomalies in its operation with no outer insulation and only the inner oven operating. Ed Ulrich Bangert wrote: I'm not talking about crystal ovens, I'm talking about timekeeping kit in general: how to filter high frequency temperature fluctuations out, so the PLL does not have to deal with them. Ok, but in this general case you have to accept the fact, that filtering high temperature fluctuations is only ONE part of the engineering job. The second task (which I tried to point at) is: When you do already have a closed loop temperature regulation system inside what you plan to built around it, then you need to manage the filtering without mal interaction of the local temperature controller with your additional filtering stuff. The art is to make the closed temperature loop inside see only smaller temperature fluctuations but No changes otherwise. If you apply an overall change in temperature insulation to the ambient you will make the work of the inside temperature controller a lot harder because it is not prepared for that. In the aluminium box that i wrote about I have for an experiment replaced the air between the 10811 and the outer box with a material that has a significant lower temperature conductivity than standing air. You can easily watch the temperature controller go crazy with that. For a second experiment I have replaced the air with a material having lots more of thermal conductivity than air and you can watch the temperature controller go crazy with that too. You don't need sophisticated temperature measurement equipment to see the controller go crazy, just watch the frequency of the oscillator. This will tell you all about it. Things are different, if you have an influence on the controller's regulation parameters (which you do not have with a ready bought device). If you do have, then your additional provisions for filtering and insulation can easily be included into the thermal model that the temperature controller has to handle and will lead to different operation parameters of the controller. That will of course work and that is why I compared your suggestions to designing a new oven (for xtal or rubidium or whatever). Best regards Ulrich Bangert -Ursprungliche Nachricht- Von: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] Im Auftrag von Poul-Henning Kamp Gesendet: Donnerstag, 11. Juni 2009 12:50 An: Discussion of precise time and frequency measurement Betreff: Re: [time-nuts] Thunderbolt stability and ambient temperature In message e182724b9fce4b9f9e914bcc4f374...@athlon, Ulrich Bangert writes: For PLL steered devices, you want your device enclosed by a thermal mass which is again enclosed by a layer of thermal isolation. The goal is to filter/average all rapid (daily ?) external temperature influences, only letting through such slow variations (seasonal ?) which the PLL can comfortably cope with. My impression with this thread is that two sligthly different things are being discussed here: Some posters explain how a crystal oven shall be
Re: [time-nuts] Thunderbolt stability and ambient temperature
I have a General Radio 100KHz crystal oven that is inside a crafted wood box. The oven uses a mercury thermometer with a pair of wires sealed in the side to implement a bang-bang servo. The wood box will thus smooth out the square wave heat pulse. I think it came from something like an LR-1 Navy signal generator as a calibration standard. I need to put an oscillator circuit on it in order to characterize its behavior. It's on the FIFO to-do stack... Don Arnold Tibus Ed, and the big group I did run such a 10811 without the outer heater connected and without any insulation around as replacement for the original insulation and box but I did not see any fluctuations beside the normal behaviour of a 10811. (I have to admit that I did not yet run precision records, neither for the heater current nor for the frequency output. I see what I have to do soon!) This model is obviously adjusted inside to work best in an encreased environment of around 40 to 45 deg. C . I think as Ulrich does explain, blocking the heat flow significantly must deteriorate the regulating loop parameters. The life time of the oscillator electronics outside the stabilized crystal element will as well decrease... A good idea in fact to put the standard in a stable area and very slow varying temp range of around 15 deg. C underneath the house fundaments...I will think about! Did anybody ever think to apply wood as stabilizing element around an oscillator? Wood behaves a bit strange, it is on one side a not bad insulator and it does have as well a quite high heat storage capacity! (Oak with around 2.4 J/g, K., Lambda 0.17 W/m.K,, Pine around 2.7 J/g.K., Lambda 0.14 W/m.K. Water around 4.18 J/g.K., Lambda 0,604 W/m.K. Copper has 0.385 2.4 J/g, K., Lambda 401 W/m.K. at 25 deg. C. ) I consider wood a very intersting material, cheap and easy to work... Arnold On Thu, 11 Jun 2009 09:22:00 -0600, Ed Palmer wrote: Ulrich, when you changed the thermal characteristics around your 10811, how 'crazy' did it become? According to your theory, there should be differences in the schematics of the oven controllers between the single and double oven variants of the 10811. Last year I picked up a couple of those double oven 10811s from China that had the outer insulation removed. I wonder if I could see any anomalies in its operation with no outer insulation and only the inner oven operating. Ed Ulrich Bangert wrote: I'm not talking about crystal ovens, I'm talking about timekeeping kit in general: how to filter high frequency temperature fluctuations out, so the PLL does not have to deal with them. Ok, but in this general case you have to accept the fact, that filtering high temperature fluctuations is only ONE part of the engineering job. The second task (which I tried to point at) is: When you do already have a closed loop temperature regulation system inside what you plan to built around it, then you need to manage the filtering without mal interaction of the local temperature controller with your additional filtering stuff. The art is to make the closed temperature loop inside see only smaller temperature fluctuations but No changes otherwise. If you apply an overall change in temperature insulation to the ambient you will make the work of the inside temperature controller a lot harder because it is not prepared for that. In the aluminium box that i wrote about I have for an experiment replaced the air between the 10811 and the outer box with a material that has a significant lower temperature conductivity than standing air. You can easily watch the temperature controller go crazy with that. For a second experiment I have replaced the air with a material having lots more of thermal conductivity than air and you can watch the temperature controller go crazy with that too. You don't need sophisticated temperature measurement equipment to see the controller go crazy, just watch the frequency of the oscillator. This will tell you all about it. Things are different, if you have an influence on the controller's regulation parameters (which you do not have with a ready bought device). If you do have, then your additional provisions for filtering and insulation can easily be included into the thermal model that the temperature controller has to handle and will lead to different operation parameters of the controller. That will of course work and that is why I compared your suggestions to designing a new oven (for xtal or rubidium or whatever). Best regards Ulrich Bangert -Ursprungliche Nachricht- Von: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] Im Auftrag von Poul-Henning Kamp Gesendet: Donnerstag, 11. Juni 2009 12:50 An: Discussion of precise time and frequency measurement Betreff: Re: [time-nuts] Thunderbolt stability and ambient temperature In message e182724b9fce4b9f9e914bcc4f374...@athlon, Ulrich Bangert writes: For PLL
[time-nuts] E1938 question
I have one of the Chinese E1938 modules I bought about a month ago. I just tried it out on the bench, and have not had much luck with it. The 5 Volt supply never goes above 50 mA or so, none of the heaters seem to be powered looking at the hockey puck D-sub connector pins. The four leds up by the PIC (?) seem to flash once on switch on and then pulse about once a second. The other led which seems to be on the 5 V supply is on. It does oscillate, but very low since it never warms up. Is there any point in my trying to go any further with this? It seems pretty dead to me, the PIC maybe? :^( Nice museum piece perhaps, but a bit expensive for only that... Dan ac6ao ___ 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] Thunderbolt stability and ambient temperature
According to your theory, there should be differences in the schematics of the oven controllers between the single and double oven variants of the 10811. Last year I picked up a couple of those double oven 10811s from China that had the outer insulation removed. I wonder if I could see any anomalies in its operation with no outer insulation and only the inner oven operating. My understanding is that the unique double oven 10811 found in the Z3801A is not there for improved temperature stability, but simply so that this first-generation GPSDO can power up within spec in ultra cold (like minus 40) telecom environments. No other hp/Agilent instrument uses an external outer oven around the 10811 as far as I know. Does anyone on the list have access to a low temperature test chamber? It would be interesting to see how slowly a 10544 or 10811 warms up from that cold environment as compared to a more modern and compact E1938 or MTI or TBolt-style OCXO. /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] Thunderbolt stability and ambient temperature
I use to have a similar on from GR but was lost in a fire. It had a large GR metal name plate on one side. I sanded and varnished the box and had it on display for quite a long time. GR was great at stretching the mechanical limits of material to get electrical specs. -pete I have a General Radio 100KHz crystal oven that is inside a crafted wood box. The oven uses a mercury thermometer with a pair of wires sealed in the side to implement a bang-bang servo. The wood box will thus smooth out the square wave heat pulse. I think it came from something like an LR-1 Navy signal generator as a calibration standard. I need to put an oscillator circuit on it in order to characterize its behavior. It's on the FIFO to-do stack... Don Arnold Tibus Ed, and the big group I did run such a 10811 without the outer heater connected and without any insulation around as replacement for the original insulation and box but I did not see any fluctuations beside the normal behaviour of a 10811. (I have to admit that I did not yet run precision records, neither for the heater current nor for the frequency output. I see what I have to do soon!) This model is obviously adjusted inside to work best in an encreased environment of around 40 to 45 deg. C . I think as Ulrich does explain, blocking the heat flow significantly must deteriorate the regulating loop parameters. The life time of the oscillator electronics outside the stabilized crystal element will as well decrease... A good idea in fact to put the standard in a stable area and very slow varying temp range of around 15 deg. C underneath the house fundaments...I will think about! Did anybody ever think to apply wood as stabilizing element around an oscillator? Wood behaves a bit strange, it is on one side a not bad insulator and it does have as well a quite high heat storage capacity! (Oak with around 2.4 J/g, K., Lambda 0.17 W/m.K,, Pine around 2.7 J/g.K., Lambda 0.14 W/m.K. Water around 4.18 J/g.K., Lambda 0,604 W/m.K. Copper has 0.385 2.4 J/g, K., Lambda 401 W/m.K. at 25 deg. C. ) I consider wood a very intersting material, cheap and easy to work... Arnold On Thu, 11 Jun 2009 09:22:00 -0600, Ed Palmer wrote: Ulrich, when you changed the thermal characteristics around your 10811, how 'crazy' did it become? According to your theory, there should be differences in the schematics of the oven controllers between the single and double oven variants of the 10811. Last year I picked up a couple of those double oven 10811s from China that had the outer insulation removed. I wonder if I could see any anomalies in its operation with no outer insulation and only the inner oven operating. Ed Ulrich Bangert wrote: I'm not talking about crystal ovens, I'm talking about timekeeping kit in general: how to filter high frequency temperature fluctuations out, so the PLL does not have to deal with them. Ok, but in this general case you have to accept the fact, that filtering high temperature fluctuations is only ONE part of the engineering job. The second task (which I tried to point at) is: When you do already have a closed loop temperature regulation system inside what you plan to built around it, then you need to manage the filtering without mal interaction of the local temperature controller with your additional filtering stuff. The art is to make the closed temperature loop inside see only smaller temperature fluctuations but No changes otherwise. If you apply an overall change in temperature insulation to the ambient you will make the work of the inside temperature controller a lot harder because it is not prepared for that. In the aluminium box that i wrote about I have for an experiment replaced the air between the 10811 and the outer box with a material that has a significant lower temperature conductivity than standing air. You can easily watch the temperature controller go crazy with that. For a second experiment I have replaced the air with a material having lots more of thermal conductivity than air and you can watch the temperature controller go crazy with that too. You don't need sophisticated temperature measurement equipment to see the controller go crazy, just watch the frequency of the oscillator. This will tell you all about it. Things are different, if you have an influence on the controller's regulation parameters (which you do not have with a ready bought device). If you do have, then your additional provisions for filtering and insulation can easily be included into the thermal model that the temperature controller has to handle and will lead to different operation parameters of the controller. That will of course work and that is why I compared your suggestions to designing a new oven (for xtal or rubidium or whatever). Best regards Ulrich Bangert -Ursprungliche Nachricht- Von: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]
[time-nuts] IEEE - Fifty Years of Progress in Quartz Crystal Frequency Standards
maybe of interest IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society Fifty Years of Progress in Quartz Crystal Frequency Standards http://www.ieee-uffc.org/main/history.asp?file=frerking and some other historical pubs http://www.ieee-uffc.org/main/history.asp -pete ___ 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] Thunderbolt stability and ambient temperature
In message ac8514a8eeb148259e3cd49b8e468...@athlon, Ulrich Bangert writes: I'm not talking about crystal ovens, I'm talking about timekeeping kit in general: how to filter high frequency temperature fluctuations out, so the PLL does not have to deal with them. If you apply an overall change in temperature insulation to the ambient [...] Which is why I suggested using an old, unplugged fridge. Your typical time-nuts kit will not have a heatflow that can warm the interior of a fridge signifiantly, but the thermal inertia of the fridge is perfect for reducing temperature fluctuations. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] Thunderbolt stability and ambient temperature
Poul-Henning Kamp wrote: In message ac8514a8eeb148259e3cd49b8e468...@athlon, Ulrich Bangert writes: I'm not talking about crystal ovens, I'm talking about timekeeping kit in general: how to filter high frequency temperature fluctuations out, so the PLL does not have to deal with them. If you apply an overall change in temperature insulation to the ambient [...] Which is why I suggested using an old, unplugged fridge. Your typical time-nuts kit will not have a heatflow that can warm the interior of a fridge signifiantly, but the thermal inertia of the fridge is perfect for reducing temperature fluctuations. I really hate the idea of using an old fridge. After any amount of use, they have enough spilled food and drink in the cracks and crevices to smell really funky if you let them warm up with the door closed. I would much rather bang together a small closet out of 2x4's and insulate it with fiber glass than use a fridge. That said, the welding shops often use an old fridge for storage of welding rods. They rewire the door switch so that the light stays on all the time, and replace the bulb with a 100W bulb. The fridge will heat up to near the boiling point of water from just the heat of the light bulb. My environmental chamber will heat up to 70C from just the heat of the 60W bulb in the chamber. -Chuck Harris ___ 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] E1938 question
Dan Rae wrote: I have one of the Chinese E1938 modules I bought about a month ago. I just tried it out on the bench, and have not had much luck with it. The 5 Volt supply never goes above 50 mA or so, none of the heaters seem to be powered looking at the hockey puck D-sub connector pins. The four leds up by the PIC (?) seem to flash once on switch on and then pulse about once a second. The other led which seems to be on the 5 V supply is on. It does oscillate, but very low since it never warms up. Is there any point in my trying to go any further with this? It seems pretty dead to me, the PIC maybe? :^( Nice museum piece perhaps, but a bit expensive for only that... Dan ac6ao ___ 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. You did connect the 12V supply as well? The output signal level is only about +4dBm. 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] E1938 question
Dan Rae wrote: I have one of the Chinese E1938 modules I bought about a month ago. I just tried it out on the bench, and have not had much luck with it. The 5 Volt supply never goes above 50 mA or so, none of the heaters seem to be powered looking at the hockey puck D-sub connector pins. The four leds up by the PIC (?) seem to flash once on switch on and then pulse about once a second. The other led which seems to be on the 5 V supply is on. It does oscillate, but very low since it never warms up. Is there any point in my trying to go any further with this? It seems pretty dead to me, the PIC maybe? :^( Nice museum piece perhaps, but a bit expensive for only that... Dan ac6ao ___ 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. When operating correctly: 1) The green power led near the heater PMOSFETS should be on continuously 2) The green led at the other end of the board should flash at 1Hz. 3) The oven takes several minutes to warm up and the outer oven shell should be noticeably warm. If other LEDs are flashing the PIC may be locked in the wrong mode. This state can sometimes be cleared by resetting the PIC by powering it down and restarting. 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] E1938 question
Dan Rae wrote: I have one of the Chinese E1938 modules I bought about a month ago. I just tried it out on the bench, and have not had much luck with it. The 5 Volt supply never goes above 50 mA or so, none of the heaters seem to be powered looking at the hockey puck D-sub connector pins. The four leds up by the PIC (?) seem to flash once on switch on and then pulse about once a second. The other led which seems to be on the 5 V supply is on. It does oscillate, but very low since it never warms up. Is there any point in my trying to go any further with this? It seems pretty dead to me, the PIC maybe? :^( Nice museum piece perhaps, but a bit expensive for only that... Dan ac6ao ___ 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. Have you checked that the outputs of all the regulators on the board are OK. In particular the -5V rail used by the heater PMOSFET driver opamps? 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] E1938 question
Dan Rae wrote: I have one of the Chinese E1938 modules I bought about a month ago. I just tried it out on the bench, and have not had much luck with it. The 5 Volt supply never goes above 50 mA or so, none of the heaters seem to be powered looking at the hockey puck D-sub connector pins. The four leds up by the PIC (?) seem to flash once on switch on and then pulse about once a second. The other led which seems to be on the 5 V supply is on. It does oscillate, but very low since it never warms up. Is there any point in my trying to go any further with this? It seems pretty dead to me, the PIC maybe? :^( Nice museum piece perhaps, but a bit expensive for only that... Dan ac6ao ___ 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. You can also try pushing the PIC reset button near the front of the board. 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] Thunderbolt stability and ambient temperature
Most people thought it was coincidence of heat propagating up the bar just at that time, or steam. Could be, but I still think it is real. The cold end of the bar was slowly getting warmer as I carried it, but after the sudden cooling of the hot end, the cold end seemed to get hot fast. Rex, We know each material has it's own thermal conductivity. Copper is 401 W/m-K and steel only about 1/10th that, etc. It would appear from conductivity tables in books that these are fixed constants. But I wonder if near-liquid (red hot) steel has a different (e.g., even lower) value than warm or cold steel? Is metal thermal conductivity actually a fixed constant or is it a function of temperature over a wide range of temperature? If so, not only is the temperature changing when you drop the steel in water, but also the thermal conductivity of the steel. Thus, depending on how fast or slowly you cool it vs. how non-linear the conductivity is as a function of temperature, I imagine you could observe the very effect you describe. /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] Thunderbolt stability and ambient temperature
Tom Van Baak wrote: Most people thought it was coincidence of heat propagating up the bar just at that time, or steam. Could be, but I still think it is real. The cold end of the bar was slowly getting warmer as I carried it, but after the sudden cooling of the hot end, the cold end seemed to get hot fast. Rex, We know each material has it's own thermal conductivity. Copper is 401 W/m-K and steel only about 1/10th that, etc. It would appear from conductivity tables in books that these are fixed constants. But I wonder if near-liquid (red hot) steel has a different (e.g., even lower) value than warm or cold steel? Is metal thermal conductivity actually a fixed constant or is it a function of temperature over a wide range of temperature? If so, not only is the temperature changing when you drop the steel in water, but also the thermal conductivity of the steel. Thus, depending on how fast or slowly you cool it vs. how non-linear the conductivity is as a function of temperature, I imagine you could observe the very effect you describe. /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. Tom The thermal conductivity isnt constant with temperature. It also varies between different crystalline forms of the same material. This can be seen in more comprehensive tables of thermal conductivity. In particular at cryogenic temperatures the thermal conductivity can change dramatically (eg in superconductors) 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] Thunderbolt stability and ambient temperature
Thermal conductivity even varies with the same crystalline forms of the same element. Diamond has the highest known conductivity of any natural substance. Isotopically pure carbon-12 diamond has twice the conductivity of natural diamond. The thermal conductivity isnt constant with temperature. It also varies between different crystalline forms of the same material. _ Insert movie times and more without leaving Hotmail®. http://windowslive.com/Tutorial/Hotmail/QuickAdd?ocid=TXT_TAGLM_WL_HM_Tutorial_QuickAdd_062009 ___ 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] Thunderbolt stability and ambient temperature
Tom The thermal conductivity isnt constant with temperature. It also varies between different crystalline forms of the same material. This can be seen in more comprehensive tables of thermal conductivity. In particular at cryogenic temperatures the thermal conductivity can change dramatically (eg in superconductors) Bruce Excellent. Not constant; and perhaps not even linear? If you run across a thermal conductivity table for steel from say 0 to 1000 C let us know. From that graph we should be able to calculate what Rex felt when he put the red hot (1500 F?) end of the 1 inch bar into cold water. Better yet, if some metal or material has an even more pronounced thermal conductivity function it would make a great party trick. /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] Thunderbolt stability and ambient temperature
How about magnetic effects such as those seen with Galfenol etc. ? Steve --- On Thu, 6/11/09, Tom Van Baak t...@leapsecond.com wrote: From: Tom Van Baak t...@leapsecond.com Subject: Re: [time-nuts] Thunderbolt stability and ambient temperature To: Discussion of precise time and frequency measurement time-nuts@febo.com Date: Thursday, June 11, 2009, 5:54 PM Tom The thermal conductivity isnt constant with temperature. It also varies between different crystalline forms of the same material. This can be seen in more comprehensive tables of thermal conductivity. In particular at cryogenic temperatures the thermal conductivity can change dramatically (eg in superconductors) Bruce Excellent. Not constant; and perhaps not even linear? If you run across a thermal conductivity table for steel from say 0 to 1000 C let us know. From that graph we should be able to calculate what Rex felt when he put the red hot (1500 F?) end of the 1 inch bar into cold water. Better yet, if some metal or material has an even more pronounced thermal conductivity function it would make a great party trick. /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] Thunderbolt stability and ambient temperature
Thermal conductivity of iron is 0..161 at 18C, and .191 from 100C to 1245C according to my Handbook (conditions are calories per second through a plate 1 cm thick across an area of one sq. cm when the temperature difference is one deg C). Point is, that's only 3 parts per 100, not enough for the crude sensing system employed? Don Latham Tom Van Baak Tom The thermal conductivity isnt constant with temperature. It also varies between different crystalline forms of the same material. This can be seen in more comprehensive tables of thermal conductivity. In particular at cryogenic temperatures the thermal conductivity can change dramatically (eg in superconductors) Bruce Excellent. Not constant; and perhaps not even linear? If you run across a thermal conductivity table for steel from say 0 to 1000 C let us know. From that graph we should be able to calculate what Rex felt when he put the red hot (1500 F?) end of the 1 inch bar into cold water. Better yet, if some metal or material has an even more pronounced thermal conductivity function it would make a great party trick. /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. -- Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Thunderbolt stability and ambient temperature
The effect that was described was absolutely NOT a result of thermal conductivity being a function of temperature. It was a dynamic effect... a transient condition. The result of applying a short heat pulse to a long Time Constant, distributed system. Do the simulation I suggested hours ago. -John == Tom The thermal conductivity isnt constant with temperature. It also varies between different crystalline forms of the same material. This can be seen in more comprehensive tables of thermal conductivity. In particular at cryogenic temperatures the thermal conductivity can change dramatically (eg in superconductors) Bruce Excellent. Not constant; and perhaps not even linear? If you run across a thermal conductivity table for steel from say 0 to 1000 C let us know. From that graph we should be able to calculate what Rex felt when he put the red hot (1500 F?) end of the 1 inch bar into cold water. Better yet, if some metal or material has an even more pronounced thermal conductivity function it would make a great party trick. /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] Thunderbolt stability and ambient temperature
The effect that was described was absolutely NOT a result of thermal conductivity being a function of temperature. It was a dynamic effect... a transient condition. The result of applying a short heat pulse to a long Time Constant, distributed system. Do the simulation I suggested hours ago. -John == Tom The thermal conductivity isnt constant with temperature. It also varies between different crystalline forms of the same material. This can be seen in more comprehensive tables of thermal conductivity. In particular at cryogenic temperatures the thermal conductivity can change dramatically (eg in superconductors) Bruce Excellent. Not constant; and perhaps not even linear? If you run across a thermal conductivity table for steel from say 0 to 1000 C let us know. From that graph we should be able to calculate what Rex felt when he put the red hot (1500 F?) end of the 1 inch bar into cold water. Better yet, if some metal or material has an even more pronounced thermal conductivity function it would make a great party trick. /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] Thunderbolt stability and ambient temperature
J. Forster wrote: It has nothing to do with this. A long (length width) bar can simply be modeled as a long ladder of series resistors's and capacitors to ground: ---zzz---zzz---zzz ... ---zzz--- _|_ _|_ _|_ _|_ ___ ___ ___ ___ | |-|- ... |- If you put a rectangular pulse in the left end, it will emerge later and very much rounded at the right end. Either do the math or simulate it in Spice or with a handful of R's and C's and a pulse generator and scope. No inductors needed. PERIOD. That model fully accounts for your observations with the bar heated at one end. -John = Ok, but isn't that propagation rate constant? Obviously, the heat from the hot end will eventually propagate with some attenuation to the cold end. My observation was that shoving cold into the hot end seems to accelerate the propagation of heat toward the cold end. This model won't show that effect, will it? This would be a double step something like this: |--- | \ ---|\ + time | / || That 2nd opposite step won't make the first pulse propagate faster or with more apparent intensity, will it? -Rex In message 4a309b30.7000...@sonic.net, Rex writes: My observation, from doing this several times, is that the cold water quickly absorbes heat from the red end, but also seems to chase a lot of the heat quickly up toward the cold end, making the bar rapidly uncomfortable to hold. I've seen the effect you describe explained in an article somewhere, very likely New Scientist or SciAm about five years ago. When you rapidly heat or cool metals, very often changes in crystal lattice structure is involved some of them resulting in quite drastic changes to volume. Heat is essentially atoms wiggling about, and when you change the modes of freedom for the atoms, they may have to wiggle harder. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] Thunderbolt stability and ambient temperature
John That doesn't appear to reproduce what was claimed to have been observed at all. The input is more like a step function that switches from hot to cold. This allows the simulated bar to reach a steady state temperature distribution before decaying smoothly to a lower temperature. Bruce J. Forster wrote: The effect that was described was absolutely NOT a result of thermal conductivity being a function of temperature. It was a dynamic effect... a transient condition. The result of applying a short heat pulse to a long Time Constant, distributed system. Do the simulation I suggested hours ago. -John == Tom The thermal conductivity isnt constant with temperature. It also varies between different crystalline forms of the same material. This can be seen in more comprehensive tables of thermal conductivity. In particular at cryogenic temperatures the thermal conductivity can change dramatically (eg in superconductors) Bruce Excellent. Not constant; and perhaps not even linear? If you run across a thermal conductivity table for steel from say 0 to 1000 C let us know. From that graph we should be able to calculate what Rex felt when he put the red hot (1500 F?) end of the 1 inch bar into cold water. Better yet, if some metal or material has an even more pronounced thermal conductivity function it would make a great party trick. /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. ___ 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] Thunderbolt stability and ambient temperature
Perhaps the answer is somewhat more prosaic. Radiation and convective losses from the hot end of the bar are significant. In particular the radiative loss is (as a first approximation) proportional to the difference of the 4th powers of the bar temperature and ambient temperature. When one modifies the model to include radiative losses near the hot end that are in effect switched off by cooling then some overshoot can occur at the hand held end of the bar. Bruce Bruce Griffiths wrote: John That doesn't appear to reproduce what was claimed to have been observed at all. The input is more like a step function that switches from hot to cold. This allows the simulated bar to reach a steady state temperature distribution before decaying smoothly to a lower temperature. Bruce J. Forster wrote: The effect that was described was absolutely NOT a result of thermal conductivity being a function of temperature. It was a dynamic effect... a transient condition. The result of applying a short heat pulse to a long Time Constant, distributed system. Do the simulation I suggested hours ago. -John == Tom The thermal conductivity isnt constant with temperature. It also varies between different crystalline forms of the same material. This can be seen in more comprehensive tables of thermal conductivity. In particular at cryogenic temperatures the thermal conductivity can change dramatically (eg in superconductors) Bruce Excellent. Not constant; and perhaps not even linear? If you run across a thermal conductivity table for steel from say 0 to 1000 C let us know. From that graph we should be able to calculate what Rex felt when he put the red hot (1500 F?) end of the 1 inch bar into cold water. Better yet, if some metal or material has an even more pronounced thermal conductivity function it would make a great party trick. /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. ___ 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] Thunderbolt stability and ambient temperature
The problem may be due to the subjectivity of the observer, not a real effect. One dimensional heat flow along a bar will be close to the simple step function in an infinite one dimensional medium. The solution is in the form of Gauss's Error Function, and any cooling can only reduce the rate of progress and/or amplitude of the heat front. Unless heat is added to the cold end of the bar there is no way that it will heat quicker. The radiation can only be switched off by reducing the surface temperature which in turn rapidly reduces the temperature gradient driving the heat front. Thats my 2c worth, Cheers, Neville Michie On 12/06/2009, at 12:36 PM, Bruce Griffiths wrote: Perhaps the answer is somewhat more prosaic. Radiation and convective losses from the hot end of the bar are significant. In particular the radiative loss is (as a first approximation) proportional to the difference of the 4th powers of the bar temperature and ambient temperature. When one modifies the model to include radiative losses near the hot end that are in effect switched off by cooling then some overshoot can occur at the hand held end of the bar. Bruce Bruce Griffiths wrote: John That doesn't appear to reproduce what was claimed to have been observed at all. The input is more like a step function that switches from hot to cold. This allows the simulated bar to reach a steady state temperature distribution before decaying smoothly to a lower temperature. Bruce J. Forster wrote: The effect that was described was absolutely NOT a result of thermal conductivity being a function of temperature. It was a dynamic effect... a transient condition. The result of applying a short heat pulse to a long Time Constant, distributed system. Do the simulation I suggested hours ago. -John == Tom The thermal conductivity isnt constant with temperature. It also varies between different crystalline forms of the same material. This can be seen in more comprehensive tables of thermal conductivity. In particular at cryogenic temperatures the thermal conductivity can change dramatically (eg in superconductors) Bruce Excellent. Not constant; and perhaps not even linear? If you run across a thermal conductivity table for steel from say 0 to 1000 C let us know. From that graph we should be able to calculate what Rex felt when he put the red hot (1500 F?) end of the 1 inch bar into cold water. Better yet, if some metal or material has an even more pronounced thermal conductivity function it would make a great party trick. /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. ___ 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] Thunderbolt stability and ambient temperature
- Original Message - From: Bruce Griffiths bruce.griffi...@xtra.co.nz To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thursday, June 11, 2009 10:36 PM Subject: Re: [time-nuts] Thunderbolt stability and ambient temperature Perhaps the answer is somewhat more prosaic. Radiation and convective losses from the hot end of the bar are significant. In particular the radiative loss is (as a first approximation) proportional to the difference of the 4th powers of the bar temperature and ambient temperature. When one modifies the model to include radiative losses near the hot end that are in effect switched off by cooling then some overshoot can occur at the hand held end of the bar. Bruce Bruce Griffiths wrote: John That doesn't appear to reproduce what was claimed to have been observed at all. The input is more like a step function that switches from hot to cold. This allows the simulated bar to reach a steady state temperature distribution before decaying smoothly to a lower temperature. Bruce J. Forster wrote: The effect that was described was absolutely NOT a result of thermal conductivity being a function of temperature. It was a dynamic effect... a transient condition. The result of applying a short heat pulse to a long Time Constant, distributed system. Do the simulation I suggested hours ago. -John == Tom The thermal conductivity isnt constant with temperature. It also varies between different crystalline forms of the same material. This can be seen in more comprehensive tables of thermal conductivity. In particular at cryogenic temperatures the thermal conductivity can change dramatically (eg in superconductors) Bruce Excellent. Not constant; and perhaps not even linear? If you run across a thermal conductivity table for steel from say 0 to 1000 C let us know. From that graph we should be able to calculate what Rex felt when he put the red hot (1500 F?) end of the 1 inch bar into cold water. Better yet, if some metal or material has an even more pronounced thermal conductivity function it would make a great party trick. /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. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] need programmable pulse output
Hi, I am looking for a GPS module or receiver that has a programmable pulse output in time. I am trying to start two data captures a couple of hundred miles appart for a bistatic RADAR. I need to program the UTC time and maybe the increment when I want the pulses to come out. I am trying to find something relatively cheap before I go layout a board that looks at the NMEA output and gates the 1pps. Thanks, Pieter - N4IP ___ 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] Thunderbolt stability and ambient temperature
Tom Van Baak wrote: Most people thought it was coincidence of heat propagating up the bar just at that time, or steam. Could be, but I still think it is real. The cold end of the bar was slowly getting warmer as I carried it, but after the sudden cooling of the hot end, the cold end seemed to get hot fast. Rex, We know each material has it's own thermal conductivity. Copper is 401 W/m-K and steel only about 1/10th that, etc. It would appear from conductivity tables in books that these are fixed constants. But I wonder if near-liquid (red hot) steel has a different (e.g., even lower) value than warm or cold steel? Is metal thermal conductivity actually a fixed constant or is it a function of temperature over a wide range of temperature? If so, not only is the temperature changing when you drop the steel in water, but also the thermal conductivity of the steel. Thus, depending on how fast or slowly you cool it vs. how non-linear the conductivity is as a function of temperature, I imagine you could observe the very effect you describe. Tom, Red hot steel bars are quite far from being molten. They are just black body emitting a more visible light range. It is not until the bar is almost white hot that it is going to melt... generally a very bright yellow. Your bare eyes won't like it! I have heated and held all manner of steel bars in the process of welding and working steel. It always seems to me that it takes about the same amount of time for me to feel the heat. Unlike aluminum, it takes minutes for the heat of a red hot end of a steel bar to travel 2-3 feet and make that end too hot to handle. It always gets there, though. When you stick a bar in water, it lets loose a great burst of steam. The steam is hot enough to burn you quite soundly. Think about this: If your threshold for heat pain is 160F, and the bar is at 130F, how much additional heat does some 500F steam need to your hand add to make your hand uncomfortably hot? I never harden steel in water or oil with a bare hand. Always pliers. Steam does a much better job of burning you than does steel. -Chuck Harris ___ 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] Thunderbolt stability and ambient temperature
Bruce Griffiths wrote: John That doesn't appear to reproduce what was claimed to have been observed at all. The input is more like a step function that switches from hot to cold. This allows the simulated bar to reach a steady state temperature distribution before decaying smoothly to a lower temperature. Bruce Humans are terrible witnesses when it comes to judging lengths of time, and degrees of temperature. That's probably why clocks and thermometers were invented. -Chuck Harris ___ 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] Thunderbolt stability and ambient temperature
Bruce Griffiths wrote: Perhaps the answer is somewhat more prosaic. Radiation and convective losses from the hot end of the bar are significant. In particular the radiative loss is (as a first approximation) proportional to the difference of the 4th powers of the bar temperature and ambient temperature. When one modifies the model to include radiative losses near the hot end that are in effect switched off by cooling then some overshoot can occur at the hand held end of the bar. Yeah, when you dunk the rod in water, the relatively small radiative and convective losses of heat are replaced by a terrifically large conductive loss of heat. The extremely quick cooling is why you dunk the bar in water in the first place. -Chuck Harris ___ 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] need programmable pulse output
Hi Pieter, Is this what you're looking for? 1PPS TIME OFFSET COMMAND (@@Ay) The GPS receiver outputs a one pulse-per second (1PPS) signal with the rising edge placed on top of the GPS/UTC one second tic mark. The 1PPS Offset command allows the user to offset the 1PPS time mark in one nanosecond increments. This offset can be used to place the 1PPS signal anywhere within the one second epoch. This command is available in the Motorola M12T, M12+, UT+, and VP boards. For more modern boards, the same command is implemented in the I-Lotus M12M and the Navsync CW-25 module with the Motorola firmware load. Be careful if the programmable 10 MHz output on the CW-25 is of interest to you. I bought it last year and at that time it was NOT programmable with the Motorola firmware load. It's fixed at 10 MHz unless you get Navsync to do some custom development. The speed is only programmable with the NMEA firmware load. Ed RFSPACE wrote: Hi, I am looking for a GPS module or receiver that has a programmable pulse output in time. I am trying to start two data captures a couple of hundred miles appart for a bistatic RADAR. I need to program the UTC time and maybe the increment when I want the pulses to come out. I am trying to find something relatively cheap before I go layout a board that looks at the NMEA output and gates the 1pps. Thanks, Pieter - N4IP ___ 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] Thunderbolt stability and ambient temperature
Hi Tom, I do have such temperature chambers. I wil do the test with a 10544 and a 10811 over teh comming wekeend probably. Regards Bernd Neubig (DK1AG) __ AXTAL GmbH Co. KG www.axtal.com Tom Van Baak wrote: Does anyone on the list have access to a low temperature test chamber? It would be interesting to see how slowly a 10544 or 10811 warms up from that cold environment as compared to a more modern and compact E1938 or MTI or TBolt-style OCXO. ___ 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.
