[time-nuts] Heating or Cooling an LPRO (was Re: chip scale atomic clock)

Bob Camp lists at cq.nu
Thu Dec 31 20:33:45 UTC 2009


Hi

If you separate the the electronics from the physics package then you will need to think pretty hard about magnetic shielding. 

It is clear though that if you are going to run an LPRO off of batteries, you want to let it warm up. The energy savings likely outweigh the loss of reliability. 

The reliability penalty is real. I have indeed "cooked" rubidiums. In each case it was not the heater circuits or the lamp that failed. 

Bob


On Dec 31, 2009, at 3:26 PM, Magnus Danielson wrote:

> Dear Peter,
> 
> Peter Vince wrote:
>>> ...5-6 W is significantly lower than 12-13 W and should allow for simpler solutions.
>> Thanks Magnus.  If saving 7 watts is important, then OK, but I am more
>> concerned about the significantly lower MTBF quoted on page 4 of the
>> manual (the ninth page in the PDF file):
>> Amb. Temp:	20°C 	25°C 	30°C 	40°C 	50°C 	60°C
>> MTBF (hrs)	381,000	351,000	320,000	253,000	189,000	134,000
> 
> Well, the junction temperature of the heaters will lower as they burn less temperature. But the LPRO design is such that the physical package is very tightly connected to the electronics board. Separation of them would allow better temperature of those while the physical package would see about the same temperature regardless. But anyway, the point of the excersize was to show just how much cooling needs could be reduced if an external oven is applied.
> 
> Cheers,
> Magnus
> 
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