[time-nuts] Looking for good SR620 setup to compare GPS and rubidium
brooke at pacific.net
Thu Sep 7 16:46:54 EDT 2006
The most straight forward way is to make a time interval measurement
between the two 1 PPS signals.
It's good to use a BNC-T connector at the SR620 front panel and a scope
so that you can set the trigger levels at 50%.
If both sources are TTL (0 to 5 volts open circuit) and you use the 50
Ohm termination in the SR620 then the pk-pk will be 2.5 volts and a
trigger level of 1.25 volts works well.
By setting SAMPLE SIZE size to some number like 500 (seconds since your
have 1 PPS input) you can then DISPLAY either MEAN or JITTER.
The latter is a very good indication of what's going on.
w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml
David Forbes wrote:
>We have a rubidium oscillator in a laboratory here that is ripe for
>calibration against a primary standard. We have installed a Datum 9390
>GPS receiver next to it as well as an SR620 counter.
>Can any of you recommend a good operating mode to make the SR620 reveal
>the rubidium drift rate in a reasonably short time a couple days is OK)
>so that we may adjust it to near zero?
>We have both 10 MHz and 1PPS available from both sources.
>We don't currently have a logging computer connected to the SR620, but
>we can do that if needed.
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