Re: [time-nuts] temperature stability basics
In message 4cf1d64e.2010...@earthlink.net, jimlux writes: Poul-Henning Kamp wrote: We use aerogel for insulation in Mars rovers.. Those little RHUs don't put out a lot of heat, and you don't have much electronics on at night. Do you know if that is in big blocks or in granular form ? -- 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] temperature stability basics
Poul-Henning Kamp wrote: In message 4cf1d64e.2010...@earthlink.net, jimlux writes: Poul-Henning Kamp wrote: We use aerogel for insulation in Mars rovers.. Those little RHUs don't put out a lot of heat, and you don't have much electronics on at night. Do you know if that is in big blocks or in granular form ? Blocks.. They cast it (well.. more like do the reaction which makes the stuff in a sort of tray... think baking dish), then trim to size. There's a fair number of recipes around to make your own aerogel. I haven't tried it, but it seems fairly straightforward, and non-exotic. There are some process controls you need to figure out, but, hey, the same applies to baking chocolate cakes and cookies. ___ 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] temperature stability basics
In message 4cf26fe2.40...@earthlink.net, jimlux writes: Poul-Henning Kamp wrote: There's a fair number of recipes around to make your own aerogel. The CO2 route is pretty safe, but be very carefull with the alcohol route, the swedes blew up a lab with supercritical alcohol once... -- 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] temperature stability basics
jimlux wrote: Poul-Henning Kamp wrote: In message 4cf1d64e.2010...@earthlink.net, jimlux writes: Poul-Henning Kamp wrote: We use aerogel for insulation in Mars rovers.. Those little RHUs don't put out a lot of heat, and you don't have much electronics on at night. Do you know if that is in big blocks or in granular form ? Blocks.. They cast it (well.. more like do the reaction which makes the stuff in a sort of tray... think baking dish), then trim to size. There's a fair number of recipes around to make your own aerogel. I haven't tried it, but it seems fairly straightforward, and non-exotic. There are some process controls you need to figure out, but, hey, the same applies to baking chocolate cakes and cookies. Making it isnt a problem. Removing the water from it (result of the fabrication technique) without destroying its mechanical integrity is. One method is to use supercritical liquid carbon dioxide. 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] temperature stability basics
In message 4cf29e0a.2020...@xtra.co.nz, Bruce Griffiths writes: jimlux wrote: Removing the water from it (result of the fabrication technique) without destroying its mechanical integrity is. One method is to use supercritical liquid carbon dioxide. I don't think there is any other method than supercritical evaporation, but you can use any liquid which can dissolve or replace the water seamlessly. CO2 is the preference because the triplepoint is convenient, but until somebody figured that out, alcohol was used. -- 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] temperature stability basics
The two (before and after ?) pics look like they have different contrast settings. -John === In message 013e01cb8dc6$41b038a0$4001a...@lark, Alan Melia writes: I believe there is a reflective/foam insulator that is sold for setting behind (what we in UK call ) CH radiators when the are mounted on outer walls. That would meed Poul-Henning's temperature difference criteria, I think. Interesting topic may me revise some 50 year old very rusty physics Not only does it meet my criteria, I've used airflex for exactly that myself, and proven that it works with a thermal camera: http://ing.dk/artikel/96840-airflex-bag-radiatorer -- 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] temperature stability basics
FWIW: During the development of the E1938A, we tried replacing the foam insulation with a skeleton plastic frame with knife edges. The idea was that the plastic would have negligible heat conduction, leaving only air convection and radiation. We didn't see much difference between this set up and the regular foam, in terms of heater power. It also didn't make much difference with thermal gain. Also, with both this oscillator and the 10811, different kinds of foam were tried. The general consensus was that all foams were more or less similar thermally, and the important characteristics differentiating them were mechanical (ability to not maintain shape after long exposure to oven temperatures) and various other manufacturing, supply chain, regulatory and environmental issues. Rick Karlquist N6RK ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] temperature stability basics
In message 05fb5f7f819d035fdc8556f9b4842b98.squir...@webmail.sonic.net, Rick Karlquist writes: The general consensus was that all foams were more or less similar thermally, There is indeed very little difference, in particular if the foam is encapsulated so the open/closed bubble difference is eliminated. These days aerogel is the big thing, and Aspen Aerogel's spaceloft series of products are seeing a lot of use in tight spaces. It is also possible to buy aerogel as granulate, for instance from United Nuclear, but be aware that it will draw moisture like there is no water tomorrow, so always use gloves and a respiratory filter. I'm not sure the mechanical strength of aerogel would be any use for military OCXO's[1], but for lab-settings, it would work fine. Poul-Henning [1] People tend to forget that aerogel is one of the strongest materials *relative to its weight*, and at the same time the solid with the lowest density. The first thing people do on picking up a piece of aerogel is typically to crush it. -- 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] temperature stability basics
In message 52830.12.6.201.2.1290877633.squir...@popaccts.quikus.com, J. Fors ter writes: The two (before and after ?) pics look like they have different contrast settings. They are actually not before and after, they are the same image in four different representations. The first (set of four) images show the front side, where one window has an insulated radiator, and the other does not have a radiator The Second set shows the other side of the house, where one window has a uninsulated radiator, while the other window have no radiator. If you look carefully at the first set, you can even see that the insulated patch of the wall is colder than the uninsulated patch... Highly recommended way to reduce heat-loss from behind radiators. -- 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] temperature stability basics
You could probably buy enough pink fiberglass to insulate a house for what one of those cost. They might even cost more on eBay -John === How about surplus HRSI tiles off the Shuttle? On Sat, Nov 27, 2010 at 1:47 PM, Poul-Henning Kamp p...@phk.freebsd.dkwrote: In message 05fb5f7f819d035fdc8556f9b4842b98.squir...@webmail.sonic.net, Rick Karlquist writes: The general consensus was that all foams were more or less similar thermally, There is indeed very little difference, in particular if the foam is encapsulated so the open/closed bubble difference is eliminated. These days aerogel is the big thing, and Aspen Aerogel's spaceloft series of products are seeing a lot of use in tight spaces. It is also possible to buy aerogel as granulate, for instance from United Nuclear, but be aware that it will draw moisture like there is no water tomorrow, so always use gloves and a respiratory filter. I'm not sure the mechanical strength of aerogel would be any use for military OCXO's[1], but for lab-settings, it would work fine. Poul-Henning [1] People tend to forget that aerogel is one of the strongest materials *relative to its weight*, and at the same time the solid with the lowest density. The first thing people do on picking up a piece of aerogel is typically to crush it. -- 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] temperature stability basics
No more costly than big pieces of aerogel and, since NASA's acceptance standards are so high there has to be some around that failed quality checks On Sat, Nov 27, 2010 at 6:30 PM, J. Forster j...@quik.com wrote: You could probably buy enough pink fiberglass to insulate a house for what one of those cost. They might even cost more on eBay -John === How about surplus HRSI tiles off the Shuttle? On Sat, Nov 27, 2010 at 1:47 PM, Poul-Henning Kamp p...@phk.freebsd.dkwrote: In message 05fb5f7f819d035fdc8556f9b4842b98.squir...@webmail.sonic.net, Rick Karlquist writes: The general consensus was that all foams were more or less similar thermally, There is indeed very little difference, in particular if the foam is encapsulated so the open/closed bubble difference is eliminated. These days aerogel is the big thing, and Aspen Aerogel's spaceloft series of products are seeing a lot of use in tight spaces. It is also possible to buy aerogel as granulate, for instance from United Nuclear, but be aware that it will draw moisture like there is no water tomorrow, so always use gloves and a respiratory filter. I'm not sure the mechanical strength of aerogel would be any use for military OCXO's[1], but for lab-settings, it would work fine. Poul-Henning [1] People tend to forget that aerogel is one of the strongest materials *relative to its weight*, and at the same time the solid with the lowest density. The first thing people do on picking up a piece of aerogel is typically to crush it. -- 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. ___ 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] temperature stability basics
Poul-Henning Kamp wrote: In message 05fb5f7f819d035fdc8556f9b4842b98.squir...@webmail.sonic.net, Rick Karlquist writes: The general consensus was that all foams were more or less similar thermally, There is indeed very little difference, in particular if the foam is encapsulated so the open/closed bubble difference is eliminated. These days aerogel is the big thing, and Aspen Aerogel's spaceloft series of products are seeing a lot of use in tight spaces. It is also possible to buy aerogel as granulate, for instance from United Nuclear, but be aware that it will draw moisture like there is no water tomorrow, so always use gloves and a respiratory filter. I'm not sure the mechanical strength of aerogel would be any use for military OCXO's[1], but for lab-settings, it would work fine. We use aerogel for insulation in Mars rovers.. Those little RHUs don't put out a lot of heat, and you don't have much electronics on at night. ___ 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] temperature stability basics
J. Forster wrote: At this point, bits of the Shuttle are collectibles and are priced accordingly. Just like genuine Apollo bits, they aren't making it any more. What was a couple of bucks surplus in the 1960s now brings far more. FWIW, -John = No more costly than big pieces of aerogel and, since NASA's acceptance standards are so high there has to be some around that failed quality checks I don't know that you need that particular material, either. It's big claim to fame is that it's refractory.. I doubt you're going to be turning a torch on your oscillator can. In any case, the stuff is avaiablee in commercial forms from the usual sources I'd start with Thermal Ceramics ___ 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] temperature stability basics
There is a very similar material used to line restaurant vent hoods. It is some sort of ceramic foam insulation board. -Chuck Harris In any case, the stuff is avaiablee in commercial forms from the usual sources I'd start with Thermal Ceramics ___ 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] temperature stability basics
Hi Beale, From: beale be...@bealecorner.com I assume dewar flasks are limited to aerospace applications. :-) You keep your coffee hot in it! Bye, Jean-Louis Noel, OO1J ___ 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] temperature stability basics
Hi, I have been looking at a similar problem. What I have found is: many plastic foam materials have very low conduction but are transparent to long wavelength radiation, so thermal heating/cooling through them is mainly by thermal radiation. If you wrap an item in plastic foam, then a radiation barrier like aluminium foil, then more plastic then more foil etc. you can seriously reduce the heat transfer. Air is an excellent insulator if it is in cells too small to allow convection, (less than say 5mm). However light air filled materials transmit thermal radiation. The CFC gasses are used in some foams to partly absorb this radiation, but reflective foil is even better as it is shiny and emits less radiation in the first place. The sandwich idea works like this; the amount of radiative transfer (in Watts) depends on the temperature difference of two layers of foil. The distance between the layers does not affect the quantity of energy radiated. So if a shiny box with one inch of air insulation around it losses 8 watts by radiation to a surrounding box, then by putting a layer of foil in the middle you halve the temperature differences and so only have 4 watts of radiative transfer. Place 3 layers of foil (with intermediate foam layers) and it drops to 2 watts. Still in the same one inch space. Find some closed cell polyethylene that is quite thin and some very light aluminium foil and you could make many layers. Just make sure that the foil is always normal to the thermal gradient. The project is not finished yet but the thermal insulation is now going to be many times better than with just thick slabs of foam. cheers, Neville Michie On 26/11/2010, at 6:24 PM, beale wrote: In an attempt to educate myself about temperature stability, I put a temperature sensor in a 1 cube of brass wrapped in plastic packing-type bubble wrap, and compared that with another sensor outside the bubble wrap, with the whole combination in a thin nylon case just to slow down direct air drafts. I put it on the bench in the office where the ambient temperature varies up and down by a few degrees over the day. I recorded both temperatures with milli- degree resolution. Looking at the resulting plots, it looks like my thermal mass and thermal insulation on the inside sensor gives me only about a half hour lag at most relative to the outside sensor (hard to say exactly, it doesn't look like a simple one-pole filter). Note, I am not attempting any kind of ovenized control as yet, just measuring some time constants. I've read that plain bubble wrap has an R value of about 2 ft^2·° F·h/(BTU·in), while some types of rigid foam building insulation go up to R=8 (at least until the CFC gases used to blow the foam leak out). What is done in real instruments that need good thermal insulation? I assume dewar flasks are limited to aerospace applications. Photo of the block prior to bubble wrap: http://picasaweb.google.com/bealevideo/2010_11_18TempExperiment (live) plot of temperatures: http://www.pachube.com/feeds/12988 ___ 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] temperature stability basics
beale wrote: In an attempt to educate myself about temperature stability, I put a temperature sensor in a 1 cube of brass wrapped in plastic packing-type bubble wrap, and compared that with another sensor outside the bubble wrap, with the whole combination in a thin nylon case just to slow down direct air drafts. I put it on the bench in the office where the ambient temperature varies up and down by a few degrees over the day. I recorded both temperatures with milli-degree resolution. Looking at the resulting plots, it looks like my thermal mass and thermal insulation on the inside sensor gives me only about a half hour lag at most relative to the outside sensor (hard to say exactly, it doesn't look like a simple one-pole filter). Note, I am not attempting any kind of ovenized control as yet, just measuring some time constants. I've read that plain bubble wrap has an R value of about 2 ft^2·°F·h/(BTU·in), while some types of rigid foam building insulation go up to R=8 (at least until the CFC gases used to blow the foam leak out). What is done in real instruments that need good thermal insulation? I assume dewar flasks are limited to aerospace applications. foam and foil are your friends. Typically, you'll have multiple layers of foam, then foil, then foam, etc. Mass also has an effect (in increasing the time constant.. the C, as opposed to the insulation which increases the R) John Strong's Procedures in Experimental Physics has a section on thermal design (for furnaces and ovens), and is worth having a copy of.' Moore, et.al., building scientific apparatus is another winner, and has a whole chapter on precision temperature control (I have to warn you.. get these two books, and you'll contemplate, or worse, actually start, a whole raft of really interesting things to do. Everyone needs a duoplasmatron ion source, don't they? Or a 6 foot tall Geiger-Muller tube made from copper pipe and mixing bowls.) And, as you get better insulation, heat leaks (whether conducted by, say, the wires, or by air, or by IR radiation) become a bigger relative problem. ___ 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] temperature stability basics
Thermos flasks were pretty common on early crystal oscillatots, including GR, HP 107(?), and Sultzer at least. -John In an attempt to educate myself about temperature stability, I put a temperature sensor in a 1 cube of brass wrapped in plastic packing-type bubble wrap, and compared that with another sensor outside the bubble wrap, with the whole combination in a thin nylon case just to slow down direct air drafts. I put it on the bench in the office where the ambient temperature varies up and down by a few degrees over the day. I recorded both temperatures with milli-degree resolution. Looking at the resulting plots, it looks like my thermal mass and thermal insulation on the inside sensor gives me only about a half hour lag at most relative to the outside sensor (hard to say exactly, it doesn't look like a simple one-pole filter). Note, I am not attempting any kind of ovenized control as yet, just measuring some time constants. I've read that plain bubble wrap has an R value of about 2 ft^2·°F·h/(BTU·in), while some types of rigid foam building insulation go up to R=8 (at least until the CFC gases used to blow the foam leak out). What is done in real instruments that need good thermal insulation? I assume dewar flasks are limited to aerospace applications. Photo of the block prior to bubble wrap: http://picasaweb.google.com/bealevideo/2010_11_18TempExperiment (live) plot of temperatures: http://www.pachube.com/feeds/12988 ___ 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] temperature stability basics
Worse. Those books will start you thinking about home brew H MASERS. T^hey make UHV seem doable. -John === John Strong's Procedures in Experimental Physics has a section on thermal design (for furnaces and ovens), and is worth having a copy of.' Moore, et.al., building scientific apparatus is another winner, and has a whole chapter on precision temperature control (I have to warn you.. get these two books, and you'll contemplate, or worse, actually start, a whole raft of really interesting things to do. Everyone needs a duoplasmatron ion source, don't they? Or a 6 foot tall Geiger-Muller tube made from copper pipe and mixing bowls.) And, as you get better insulation, heat leaks (whether conducted by, say, the wires, or by air, or by IR radiation) become a bigger relative problem. ___ 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] temperature stability basics
In message 4cefd115.5030...@earthlink.net, jimlux writes: beale wrote: What is done in real instruments that need good thermal insulation? I assume dewar flasks are limited to aerospace applications. One good allround foam material is Armaflex -- 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] temperature stability basics
Hi The other answer is to let the temperature control electronics take care of the problem. If you are doing something inside that uses energy (like an oscillator) it have generate a heat rise through the insulation. Bob Sent from my iPhone On Nov 26, 2010, at 2:24 AM, beale be...@bealecorner.com wrote: In an attempt to educate myself about temperature stability, I put a temperature sensor in a 1 cube of brass wrapped in plastic packing-type bubble wrap, and compared that with another sensor outside the bubble wrap, with the whole combination in a thin nylon case just to slow down direct air drafts. I put it on the bench in the office where the ambient temperature varies up and down by a few degrees over the day. I recorded both temperatures with milli-degree resolution. Looking at the resulting plots, it looks like my thermal mass and thermal insulation on the inside sensor gives me only about a half hour lag at most relative to the outside sensor (hard to say exactly, it doesn't look like a simple one-pole filter). Note, I am not attempting any kind of ovenized control as yet, just measuring some time constants. I've read that plain bubble wrap has an R value of about 2 ft^2·°F·h/(BTU·in), while some types of rigid foam building insulation go up to R=8 (at least until the CFC gases used to blow the foam leak out). What is done in real instruments that need good thermal insulation? I assume dewar flasks are limited to aerospace applications. Photo of the block prior to bubble wrap: http://picasaweb.google.com/bealevideo/2010_11_18TempExperiment (live) plot of temperatures: http://www.pachube.com/feeds/12988 ___ 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] temperature stability basics
One thing to be aware of with the LM35 type of sensors in the TO92 package is that virtually all of the temperature input to the chip is via the leads (fine print in the data sheet). I have seen several places with the device package epoxied to some surface or embedded in some insulation with the leads hanging out in the air. ___ 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] temperature stability basics
namic...@gmail.com said: Find some closed cell polyethylene that is quite thin and some very light aluminium foil and you could make many layers. How about aluminized Mylar? If the many-reflective-layers idea really works, I'd expect somebody to sell foam built that way. Why don't they? -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] temperature stability basics
That's what those golden thermal blankets are on spacecraft and in cryostats. I'm not quite sure whether the golden color comes from a deposited film of Au, or whether it's color comes from the Mylar. It's more likely the former. I've seen the stuff up close, but have not worked wit it personally. Anyway, the blankets are made of a mulit-layer sandwich of the film and something like spider web as spacers between layers. In vacuum there is no convective transfer, the spider spacers reduce conduction, and the metalization reduces radiation. Best, -John . namic...@gmail.com said: Find some closed cell polyethylene that is quite thin and some very light aluminium foil and you could make many layers. How about aluminized Mylar? If the many-reflective-layers idea really works, I'd expect somebody to sell foam built that way. Why don't they? -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] temperature stability basics
Hal Murray wrote: namic...@gmail.com said: Find some closed cell polyethylene that is quite thin and some very light aluminium foil and you could make many layers. How about aluminized Mylar? If the many-reflective-layers idea really works, I'd expect somebody to sell foam built that way. Why don't they? Maybe demand is small for such a product? They do make thin metal/fabric multi layer stuff (for things like exhaust systems) where the fabric is something moderately refractory (fiberglass? ceramic wool?) And, for spacecraft (a very small volume application) look up multilayer insulation or MLI. ___ 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] temperature stability basics
J. Forster wrote: That's what those golden thermal blankets are on spacecraft and in cryostats. I'm not quite sure whether the golden color comes from a deposited film of Au, or whether it's color comes from the Mylar. It's more likely the former. I've seen the stuff up close, but have not worked wit it personally. Anyway, the blankets are made of a mulit-layer sandwich of the film and something like spider web as spacers between layers. In vacuum there is no convective transfer, the spider spacers reduce conduction, and the metalization reduces radiation. http://en.wikipedia.org/wiki/Multi-layer_insulation I like the pseudo technical phrase constructed with sewing technology.. rather than the simpler sewn. Spacesuits use it too. beta cloth as the separator in a lot of cases. ___ 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] temperature stability basics
Hi The gold color in a space thermal blanket is from - gold. The normal formula is to use gold leaf and tissue paper (not quite the Kleenex variety, but similar) in layers. The gold leaf is *very* good for IR reflection. The tissue paper is porous enough that there's very little air trapped in it. The real insulation is the vacuum (courtesy of mother nature). The gold leaf and the spacer material just take care of the IR part of the equation without adding a lot of conductivity. Bob On Nov 26, 2010, at 5:43 PM, J. Forster wrote: That's what those golden thermal blankets are on spacecraft and in cryostats. I'm not quite sure whether the golden color comes from a deposited film of Au, or whether it's color comes from the Mylar. It's more likely the former. I've seen the stuff up close, but have not worked wit it personally. Anyway, the blankets are made of a mulit-layer sandwich of the film and something like spider web as spacers between layers. In vacuum there is no convective transfer, the spider spacers reduce conduction, and the metalization reduces radiation. Best, -John . namic...@gmail.com said: Find some closed cell polyethylene that is quite thin and some very light aluminium foil and you could make many layers. How about aluminized Mylar? If the many-reflective-layers idea really works, I'd expect somebody to sell foam built that way. Why don't they? -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ 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] temperature stability basics
Aren't the space blankets use in survival packs pretty much the same stuff? The mylar-air space-mylar construction seems pretty rational, and they are windproof. -John === Hal Murray wrote: namic...@gmail.com said: Find some closed cell polyethylene that is quite thin and some very light aluminium foil and you could make many layers. How about aluminized Mylar? If the many-reflective-layers idea really works, I'd expect somebody to sell foam built that way. Why don't they? Maybe demand is small for such a product? They do make thin metal/fabric multi layer stuff (for things like exhaust systems) where the fabric is something moderately refractory (fiberglass? ceramic wool?) And, for spacecraft (a very small volume application) look up multilayer insulation or MLI. ___ 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] temperature stability basics
Not leaf in the ones I've seen. It's very clearly a metalized plastic film. Gold leaf has virtually no structural strength. A breeze will tear it. I also doubt any tissue paper usage. Best, -John = Hi The gold color in a space thermal blanket is from - gold. The normal formula is to use gold leaf and tissue paper (not quite the Kleenex variety, but similar) in layers. The gold leaf is *very* good for IR reflection. The tissue paper is porous enough that there's very little air trapped in it. The real insulation is the vacuum (courtesy of mother nature). The gold leaf and the spacer material just take care of the IR part of the equation without adding a lot of conductivity. Bob On Nov 26, 2010, at 5:43 PM, J. Forster wrote: That's what those golden thermal blankets are on spacecraft and in cryostats. I'm not quite sure whether the golden color comes from a deposited film of Au, or whether it's color comes from the Mylar. It's more likely the former. I've seen the stuff up close, but have not worked wit it personally. Anyway, the blankets are made of a mulit-layer sandwich of the film and something like spider web as spacers between layers. In vacuum there is no convective transfer, the spider spacers reduce conduction, and the metalization reduces radiation. Best, -John . namic...@gmail.com said: Find some closed cell polyethylene that is quite thin and some very light aluminium foil and you could make many layers. How about aluminized Mylar? If the many-reflective-layers idea really works, I'd expect somebody to sell foam built that way. Why don't they? -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ 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] temperature stability basics
I believe there is a reflective/foam insulator that is sold for setting behind (what we in UK call ) CH radiators when the are mounted on outer walls. That would meed Poul-Henning's temperature difference criteria, I think. Interesting topic may me revise some 50 year old very rusty physics :-)) Alan G3NYK - Original Message - From: jimlux jim...@earthlink.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, November 26, 2010 11:41 PM Subject: Re: [time-nuts] temperature stability basics Hal Murray wrote: namic...@gmail.com said: Find some closed cell polyethylene that is quite thin and some very light aluminium foil and you could make many layers. How about aluminized Mylar? If the many-reflective-layers idea really works, I'd expect somebody to sell foam built that way. Why don't they? Maybe demand is small for such a product? They do make thin metal/fabric multi layer stuff (for things like exhaust systems) where the fabric is something moderately refractory (fiberglass? ceramic wool?) And, for spacecraft (a very small volume application) look up multilayer insulation or MLI. ___ 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] temperature stability basics
Hi The ones I'm talking about aren't used anywhere there's air to create any wind Bob On Nov 26, 2010, at 6:52 PM, J. Forster wrote: Not leaf in the ones I've seen. It's very clearly a metalized plastic film. Gold leaf has virtually no structural strength. A breeze will tear it. I also doubt any tissue paper usage. Best, -John = Hi The gold color in a space thermal blanket is from - gold. The normal formula is to use gold leaf and tissue paper (not quite the Kleenex variety, but similar) in layers. The gold leaf is *very* good for IR reflection. The tissue paper is porous enough that there's very little air trapped in it. The real insulation is the vacuum (courtesy of mother nature). The gold leaf and the spacer material just take care of the IR part of the equation without adding a lot of conductivity. Bob On Nov 26, 2010, at 5:43 PM, J. Forster wrote: That's what those golden thermal blankets are on spacecraft and in cryostats. I'm not quite sure whether the golden color comes from a deposited film of Au, or whether it's color comes from the Mylar. It's more likely the former. I've seen the stuff up close, but have not worked wit it personally. Anyway, the blankets are made of a mulit-layer sandwich of the film and something like spider web as spacers between layers. In vacuum there is no convective transfer, the spider spacers reduce conduction, and the metalization reduces radiation. Best, -John . namic...@gmail.com said: Find some closed cell polyethylene that is quite thin and some very light aluminium foil and you could make many layers. How about aluminized Mylar? If the many-reflective-layers idea really works, I'd expect somebody to sell foam built that way. Why don't they? -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ 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] temperature stability basics
Dont get the idea that radiation is only significant for large temperature differences. For two parallel surfaces at any distance apart the black body radiation between them (around room temperature 300K) is near to 6 watts per square metre per degree (C*) of temperature difference. That is an R rating of 0.14 in parallel with the conduction through the insulation that is IR transparent. The rate is proportional to the temperature difference. The fourth power law only becomes significant when the temperature difference is quite large. If the surface is clean and polished the emmissivity of the surface can be significantly reduced, hence the silver lining in a dewar. With sheet materials, an oil film, corrosion and dust can rapidly increase the emmisivity. Gold is good because of its freedom from oxidation and discolouring and ease of flashing onto any surface. If you make a sandwich with N layers of metal foil, the radiation transmission is reduced by 1/N. Cheers, Neville Michie ___ 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] temperature stability basics
Bob Camp wrote: Hi The gold color in a space thermal blanket is from - gold. The normal formula is to use gold leaf and tissue paper (not quite the Kleenex variety, but similar) in layers. The gold leaf is *very* good for IR reflection. The tissue paper is porous enough that there's very little air trapped in it. The real insulation is the vacuum (courtesy of mother nature). The gold leaf and the spacer material just take care of the IR part of the equation without adding a lot of conductivity. Bob I'm pretty sure they don't use tissue paper anymore.. Too many particulates and/or outgassing.. (and, cynically, too cheap) But really, if you've got optical instruments on the spacecraft, particulates and outgassing are a big, big deal. And, if you're heading to somewhere interesting, planetary protection means that you need to be able to cook it at a high temperature to kill everything. ___ 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] temperature stability basics
Bob Camp wrote: Hi The ones I'm talking about aren't used anywhere there's air to create any wind Bob yeah, but there's plenty of handling and air currents before it gets launched...grin These days, I'd vote for evaporated metal on some substrate. ___ 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] temperature stability basics
I'm virtually certain by 1968 they were using some plastic film. Maybe Mylar, maybe Kapton, but metalized plastic. I was doing optics and telemetry so was not really involved in other areas, but I babysat our payload on that bird first bird for 5 months -John Bob Camp wrote: Hi The ones I'm talking about aren't used anywhere there's air to create any wind Bob yeah, but there's plenty of handling and air currents before it gets launched...grin These days, I'd vote for evaporated metal on some substrate. ___ 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] temperature stability basics
Hi It's a fused fiber material, more like the stuff they make overnight shipping envelopes out of than a normal paper. It looks and feels more like tissue paper than anything else though. The same outgassing and particles floating around issues mess up the gaps in the sandwich. There are indeed papers on the stuff. It's pretty common. Bob On Nov 26, 2010, at 9:34 PM, jimlux wrote: Bob Camp wrote: Hi The ones I'm talking about aren't used anywhere there's air to create any wind Bob yeah, but there's plenty of handling and air currents before it gets launched...grin These days, I'd vote for evaporated metal on some substrate. ___ 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] temperature stability basics
In message 013e01cb8dc6$41b038a0$4001a...@lark, Alan Melia writes: I believe there is a reflective/foam insulator that is sold for setting behind (what we in UK call ) CH radiators when the are mounted on outer walls. That would meed Poul-Henning's temperature difference criteria, I think. Interesting topic may me revise some 50 year old very rusty physics Not only does it meet my criteria, I've used airflex for exactly that myself, and proven that it works with a thermal camera: http://ing.dk/artikel/96840-airflex-bag-radiatorer -- 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] temperature stability basics
In an attempt to educate myself about temperature stability, I put a temperature sensor in a 1 cube of brass wrapped in plastic packing-type bubble wrap, and compared that with another sensor outside the bubble wrap, with the whole combination in a thin nylon case just to slow down direct air drafts. I put it on the bench in the office where the ambient temperature varies up and down by a few degrees over the day. I recorded both temperatures with milli-degree resolution. Looking at the resulting plots, it looks like my thermal mass and thermal insulation on the inside sensor gives me only about a half hour lag at most relative to the outside sensor (hard to say exactly, it doesn't look like a simple one-pole filter). Note, I am not attempting any kind of ovenized control as yet, just measuring some time constants. I've read that plain bubble wrap has an R value of about 2 ft^2·°F·h/(BTU·in), while some types of rigid foam building insulation go up to R=8 (at least until the CFC gases used to blow the foam leak out). What is done in real instruments that need good thermal insulation? I assume dewar flasks are limited to aerospace applications. Photo of the block prior to bubble wrap: http://picasaweb.google.com/bealevideo/2010_11_18TempExperiment (live) plot of temperatures: http://www.pachube.com/feeds/12988 ___ 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.
