[time-nuts] Stanford Research SR620 Measurement Bias

Jürg Kögel j.koegel5 at gmail.com
Wed Sep 30 14:05:46 UTC 2009

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,
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

Best regards

Jürg Kögel

2009/9/28 Magnus Danielson <magnus at rubidium.dyndns.org>:
> Ulrich,
> Ulrich Bangert wrote:
>> Stan,
>> I believe I made it with calbyte 4 as described on page 71 of the manual.
> How does that explains the shift with time-base?
> I think it is the wrong way around for a time-bias like this. Tweaking the
> time-base will maybe fix it for one of the time-bases, but not for the
> others.
> I'm digging deeper into this, I want to know how to fix it if I see it on
> mine.
> Cheers,
> Magnus
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