Thanks for the tip! Your method eliminates the interaction between the effects of the CalByte 50 and CalByte 4 adjustments in a way that makes perfect sense. After some trial and error, I found that it's easier to get the CalByte 50 adjustment right using the short (0.01 s) timebase setting rather than the long (1 s). My SR620 is now a whole lot more accurate and the bias is essentially gone.
My one complaint is that I can't see the actual counter readings while I'm adjusting the CalByte values. I haven't looked into this yet, but are the readings being outputted from the scope or printer outputs on the rear panel during the cal adjustments? Stan Message: 1 Date: Wed, 30 Sep 2009 16:05:46 +0200 From: J?rg K?gel <[email protected]> Subject: Re: [time-nuts] Stanford Research SR620 Measurement Bias To: Discussion of precise time and frequency measurement <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1 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 Best regards J?rg K?gel _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
