Hi A few words of caution here.
I have run compact rubidiums for a number of years. It is *very* tempting to skimp on the heat sink. Cooling something that's heating it's self up sounds silly. Having tried the "not much heat sink" approach several times (I'm a slow learner). The rubidium does die fairly soon. Properly cooled they last for a long time. You need to get the baseplate below 40 C. Getting it below 30 C might be better, but that's impractical in most settings. The units dump around 10 watts of heat. The number will vary depending on the supply voltage, the exact baseplate temperature, and the exact model. If your normal room temperature is 20 C, 10 watts and a rise to 40 gives you 2 C/W. In a tightly packed rack, in the summer, at high supply voltage, the heat sink required can easily get to < 1 C/W. My answer to that is to move the rubidium out of the rack or simply turn it off when things get that warm. Fans are a good way to improve the efficiency of any heat sink. The problem here is that rubidiums are sensitive to magnetic field. Having a device with a magnetic motor in it right next to one probably is a bad idea. If you put in fans, put them in the back of the case, and keep them away from the rubidium. Bob On Feb 28, 2010, at 10:55 AM, Joe Gwinn wrote: > At 2:02 AM +0000 2/28/10, time-nuts-requ...@febo.com wrote: >> Date: Sat, 27 Feb 2010 20:02:05 -0600 >> From: Ed Palmer <ed_pal...@sasktel.net> >> Subject: Re: [time-nuts] Rack-mounting an LPRO? >> To: Discussion of precise time and frequency measurement >> <time-nuts@febo.com> >> Message-ID: <4b89ce9d.4060...@sasktel.net> >> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed" >> >> Sorry, the pictures got lost. Let's try again. >> >> Ed Palmer wrote: >>> What else is going to be in the rack? If your 1U enclosure is packed >>> in tight between other devices there might be no cooling at all. You >>> might need a fan to move some air. >>> >>> I don't know if you can find something like this, but I scavenged heat >>> sinks from an old Compaq DL760 server that might fit your situation. >>> Here's what the heat sink looks like. The aluminum plate is about >>> 1/4" (6.4 mm) thick. Notice the heat pipes. >>> >>> >>> >>> Here's what it looks like on the LPRO. You'll have to drill holes in >>> the plate to match the LPRO. >>> >>> >>> >>> It's not perfect, but it certainly does the job - particularly if you >>> had a fan blowing through the fins. The total height is about 1.75" >>> (45 mm). >>> >>> But remember, the more you cool the LPRO, the more power it will draw >>> to keep itself warm so you don't want to overdo the cooling. >>> >> > Ed >>> >> [snip] >> -------------- next part -------------- >> A non-text attachment was scrubbed... >> Name: 1.jpg >> Type: image/jpeg >> Size: 37469 bytes >> Desc: not available >> URL: >> <http://www.febo.com/pipermail/time-nuts/attachments/20100227/9f21a5a8/attachment.jpg> >> -------------- next part -------------- >> A non-text attachment was scrubbed... >> Name: 2.jpg >> Type: image/jpeg >> Size: 33025 bytes >> Desc: not available >> URL: >> <http://www.febo.com/pipermail/time-nuts/attachments/20100227/9f21a5a8/attachment-0001.jpg> > > The aluminum fin and copper pipe assembly integrated with the heatsink plate > is most likely a heat pipe of some kind, as that's what Thermacore makes. > It's a model 2644, from the nameplate, but no joy at the Thermacore.com > website. > > Joe Gwinn > > _______________________________________________ > 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.
