[time-nuts] Operating temperatures of rubidium oscillators
Mark Sims
holrum at hotmail.com
Thu Jun 12 13:44:51 EDT 2008
I recently measured the operating (baseplate) temperatures of several different rubidium standards. These are all in free air without heatsinks. Results are as follows (degrees C over ambient, warmest point found on device):
FRK-L: +21C
M100: +18C
LPRO: +24C
5650A: +35C
PTB100: +12C
The FRK-L mounted on a heatsink with around 80 square inches of heatsink fins had a 11C rise. The fins were in contact with a table, with the device pointing up.
The LPRO was operated with the baseplate in a vertical orientation at 24V. The FRK and M100 with the baseplate in contact with a table at 27V. The 5650A was operated at 15V with the baseplate vertical.
The PTB-100 is essentially an FRK-H with a heatsink that is mounted in a Tektronix TM-500 module.
It appears all the devices can be safely operated in a room temperature environment without heat sinks, but for highest reliability and longest life one should provide some form of heat control. The FRK/M100/LPRO would probably be fine with their baseplates secured to a metal chassis. The FEI-5650A is very close to its maximum specified operating temperature (65C). It would probably exceed the spec if enclosed in a case without airflow. Just a little moving air goes a long way to keeping things cool. Passive cooling with just a heatsink tends to be rather ineffective.
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