[time-nuts] Considerations When Using The SR620

Paul DeStefano paul.destefano at willamettealumni.com
Sun Dec 2 19:45:50 UTC 2012


 	The following comment appeared on this list recently and it scared 
me a little:

> Though the SR620 TIC is a great instrument when hunting the pico seconds 
> we have to realize, that it's a thermal design desaster (I have to 
> apologize to all sr620 friends). I have to run it for at least 12 
> hoursif not 24 to be shure, that every single part is at a more or less 
> stationary thermal state. Some (NERC) say "...never switch it off".

I assume this instability is due to the instability of the internal 
frequency standard.  There are two options for the SR620: the standard 
oscillator and an ovenized oscillator.  In fact, in our measurements, we 
plan to use a Cesium frequency standard as the timebase to our SR620. 
Does this anecdotal warning apply generally to the instrument or mainly to 
the use of the internal standard oscillator?

We are using the SR620 to measure the interval between 1PPS signals from 
two clocks.  One is the Septentrio PolaRx4 GPS receiver and the other is a 
Rubidium clock.

Many Thanks,

Paul DeStefano

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