[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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