[time-nuts] Stanford Research SR620 Measurement Bias

[Stan]

One last follow-on to this thread: In order to speed up the calibration
process by being able to see the measurement results in real time while
adjusting the two CalByte values, I connected the SR620 scope outputs and
monitored the graphical output on my oscilloscope. It turns out that the
graphical output still works while adjusting the CalBytes and makes the
setup simpler (for me, anyway) than using a terminal emulator on the SR620
serial port to make the adjustments.

Stan

Message: 1
Date: Wed, 30 Sep 2009 16:05:46 +0200
From: J?rg K?gel <j.koegel5 at gmail.com>
Subject: Re: [time-nuts] Stanford Research SR620 Measurement Bias
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Message-ID:
	<390229150909300705v1808d748h5376cf05e7ae637a at mail.gmail.com>
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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