Hi The short term stability *may* improve with temperature stabilization, even if the static temperature performance is fairly good.
Since all of the rubidium guys sell parts with many different options. Trying to find out exactly what the rubidium you have in your hand does can be difficult. I suspect that testing the actual device may be the only sure way to do it. Bob On Dec 28, 2009, at 10:52 AM, ewkeh...@aol.com wrote: > Hi > With all the dialog on controlling temperature of the Rb unit I decided to > take my Frequency Electronics Inc. 5062B apart since the Oven Controlled > Oscillator and Rb Physics Package are separate and I may want to replace the > oscillator with a HP 10811 that Corby has tested to be better than 1 E 12 > from 1 to 100 sec. > In order to proceed it would help if any one out there has any information > on the circuitry, the unit has two modules and two PC boards. The boards > are power supply and synthesizer and the modules are Rb unit and oscillator. > I have opened the Rb unit and I am convinced that it can be a candidate for > heat pipe cooling. Since it can be operated separate from the rest of the > unit it will be possible to measure heat rise. > The published plot of a 5600 shows a temp performance of +- 3 E -11 from > -5 to +45 C. I am not sure if there is room for improvement. > Any help would be greatly appreciated. > > > Bert Kehren WB5MZJ Miami > > > > In a message dated 12/27/2009 2:18:14 P.M. Eastern Standard Time, > li...@cq.nu writes: > > Hi > > The tip it and listen to it slam test is a standard way of checking out a > triple point of water cell for basically the same reason (you check the > vacuum. Of course since a TWP cell is thin glass and not a nice metal pipe, > you *may* break the seal by testing it .... > > Bob > > > On Dec 27, 2009, at 9:33 AM, Joe Gwinn wrote: > >> At 12:00 PM +0000 12/27/09, time-nuts-requ...@febo.com wrote: >>> >>> Date: Sat, 26 Dec 2009 17:04:46 -0700 >>> From: Robert Darlington <rdarling...@gmail.com> >>> Subject: Re: [time-nuts] Cheap Rubidium (heatpipe cooling for) >>> To: Discussion of precise time and frequency measurement >>> <time-nuts@febo.com> >>> >>> My comments are in-line, below.... >>> >>> On Fri, Dec 25, 2009 at 4:38 PM, Joe Gwinn <joegw...@comcast.net> wrote: >>> >>>> At 12:45 AM +0000 12/25/09, time-nuts-requ...@febo.com wrote: >>>> >>>>> >>>>> Date: Thu, 24 Dec 2009 17:14:38 -0700 >>>>> From: Robert Darlington <rdarling...@gmail.com> >>>>> Subject: Re: [time-nuts] Cheap Rubidium (heatpipe cooling for) >>>>> To: Discussion of precise time and frequency measurement >>>>> <time-nuts@febo.com> >>>>> >>>>> >>>>> On Thu, Dec 24, 2009 at 1:32 PM, Bob Camp <li...@cq.nu> wrote: >>>>> >>>>> Hi >>>>>> >>>>>> A heat pipe might work if the fluid had a sufficiently low boiling >>>>>> point. >>>>>> >>>>> >>>>> >>>>> The working fluid in a heat pipe will boil at every temperature above > its >>>>> melting point. >>>>> >>>> >>>> Well, I've been thinking about this, and I used the term "heat pipe" > too >>>> loosely. Both the one- and two-pipe systems mentioned here have no > wicks, >>>> and so technically are two-phase thermosyphons, which depend on > gravity to >>>> circulate vapor and condensate. A true heat pipe has a wick, and will > work >>>> in zero gravity. >>>> >>>> One gets significant heat transfer by phase change so long as the vapor >>>> pressure in the heat input end is high enough to generate enough vapor > to >>>> carry the thermal power flow, and this makes the pipe isothermal. > However >>>> the temperature (although constant along the pipe) varies with the > thermal >>>> power flow (in thermal watts) being carried. >>>> >>>> What I'm looking for is related but different: A device where the > heat >>>> transfer capacity varies sharply with temperature, so that there is a > range >>>> of heat transfer rates over which the input-end temperature will be >>>> substantially constant. This is why I envision the fluid boiling > (versus >>>> evaporating), which is actually out of the operating regime of a true > heat >>>> pipe. >>>> >>>> >>>>> I tend to use water because it's cheap, but have made them >>>>> with 3M "engineered fluids", Fluorinert, and denatured alcohol. >>>> >>>> Fluorinert. I think that's what the expensive commercial CPU-cooling >>>> heatpipes use. >>>> >>> $1000 a gallon! Or $5 a drum when you buy it at a salvage auction. >> >> That explains why low-end heatpipes use alcohol or acetone. >> >> Actually, one ought to be able to use the freon intended for automobile > air conditioners, for a whole lot less money, even new. >> >> >>>>> I've found >>>>> that ordinary solder works just fine. A trick to make these things > easy >>>>> to build is to use a ball valve at the top (I'm assuming there is a > top and >>>>> we're going with gravity return because it's simple). I've got a few > that >>>>> are still under vacuum for several years now in this configuration. > My >>>>> giant heat pipe of doom is a 10 foot stick of 1/2" copper with a ball > valve >>>>> at one end and an end cap at the other. There is perhaps 100ml water > in >>>>> there total, and no air. You can either boil the liquid until it > builds up >>>>> a nice head of steam, or go the easy way and pull a vacuum with a > pump and >>>>> just close the valve. >>>> >>>> I wouldn't have thought that an ordinary ball valve would be tight > enough, >>>> allowing the water to escape and the air enter, slowly, although I > suppose >>>> one can replace the water if it comes to that. >>>> >>> Mine have been running for a few years with no sign of needing to be > pumped >>> down again. They just work. >>> >>>> But I think people want to build this exactly once, so I followed >>>> refrigeration practice. A properly made hermetically sealed > refrigeration >>>> system keeps its working fluid essentially forever. I suppose one can > use a >>>> refrigeration fill valve, say from an automobile air conditioning > system, >>>> but these all leak to some degree. >>>> >>>> Is the ball valve anything special? >>>> >>> Nope, just whatever was on the shelf at the local hardware store. >>> Stainless ball with brass valve body. Teflon bearing surface. >> >> Ahh. A quarter-turn ball valve, used as a cutoff. The term "ball > valve" isn't quite precise in plumbing parlance. >> >> These are very good, but still they are not hermetic, and will over > decades (if not a few years) lose their working fluid. I bet that while > water > will be contained, freon will diffuse right through the teflon seal of the > ball valve. So, there's the tradeoff. >> >> >>>>> These things are incredible. If you pack snow around >>>>> the end of this thing, the other end that is ten feet away gets cold > almost >>>>> immediately. They want to stay isothermal and the heat transfer is > at the >>>>> speed of sound through the working fluid. Delays are introduced > because >>>>> you're dealing with a thermal mass of copper pipe that needs to change >>>>> temperature along with the working fluid so it's not quite instant, > but >>>>> still about 10,000 times faster heat transfer than copper by itself. > They >>>>> are certainly handy for getting heat out of confined spaces. >>>>> >>>> >>>> What is the purpose of the heatpipe of doom? Education? >>>> >>> Education, fun, and then later a demonstration piece. It's fun to > rapidly >>> move the thing along its axis, upward and then stop. The slug of water >>> moves up and then slams back down to the bottom and sounds like a steel > ball >>> in the pipe. It makes a satisfying clang sound. A couple of years > back >>> when I did a demo, people were convinced I had a metal part in there > that >>> was loose. I opened the valve and out came a 100ml water and nothing >>> else. Too cool, and you can make them at home for next to nothing. >> >> This definitely sounds like a good physics demo for school use. >> >> >>> Before >>> I started using vacuum pumps to pump them down, I'd use a blowtorch to > boil >>> the water and use the valve to throttle the steam coming out. Once the >>> steam is coming out really fast you basically just quickly close the > valve >>> and remove from the heat source. That's it! For smaller diameter > pipes I >>> use other methods and other working fluids because heating tends to > just >>> eject the sometimes very expensive fluid. >> >> What sizes, what fluids, what purposes? >> >> >> Joe >> >> _______________________________________________ >> 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.
