[time-nuts] Stanford Research SR620 Measurement Bias

Magnus Danielson magnus at rubidium.dyndns.org
Wed Sep 30 16:17:36 UTC 2009

Hi Jürg,

Jürg Kögel wrote:
> Make the adjustment in the correct sequence:
> 1. Set the Cal jumper to Cal Enable
> 2. Connect the reference to Ext Ref (rear) and Input A
> 3. Switch the counter to Ext Ref
> 4. Set the CalByte 50 for the best display (this is a very fine adjustement)
> 5. Switch the counter to Int Ref
> 6. Set the CalByte 4 for the best display (this adjustement is coarse,
> optimize!)
> 7. Set the Cal jumper to Cal Disable
> After this calibration my SR620 is
> with the external reference  +/- 3 counts  (9'999'999.9997x....10'000'000,0003)
> previous value   -210 counts
> with the internal reference  +/- 6 counts
> previous value   -25 counts

Thanks for that clarification. It seems very reasnoble. I obviously 
never bothered to do a carefull calibration of my SR620, so I haven't 
picked up the fine grain details involved with these procedures. This is 
a good reminder that I should pay attention to those details. I think I 
can say the same for most of my gear.


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