I would be interested in those scripts as well. as soon as the replacement TCXO for my sr620 arrives I can put it back together and this would be fun to try.
-eric On Tue, Dec 4, 2012 at 5:11 AM, Tom Van Baak <t...@leapsecond.com> wrote: > > We are using the SR620 to measure the interval between 1PPS signals from > > two clocks. One is the Septentrio PolaRx4 GPS receiver and the other is > a > > Rubidium clock. > > > > Many Thanks, > > Paul > > Hi Paul, > > 1) If you are making frequency measurements, the warm-up of the internal > oscillator is the major factor limiting accuracy. This doesn't mean you > have wait 12 hours. For example, if all you need is 6 digits of precision, > a one-minute warm-up may be sufficient. For each further digit of precision > you wait longer. You can probably get 9 digits with 1/2 hour of warm-up. It > depends on the oscillator. Plotting digits of precision as a function of > warm-up time would make a very educational graph you could tape to the top > of your SR620. > > 2) If you are making time interval measurements and using an external > standard, the warm-up time will also affect the accuracy of your TI > measurements, but to a far lesser degree. Here are informal results for TI > (time interval) mode after a 5 minute power-down (see also attached plots): > > - if you need 1 ns accuracy, you can use the SR620 immediately after > power-up > - if you need 100 ps accuracy, wait 2+ minutes > - if you need 10 ps accuracy, wait 15+ minutes > - if you need 1 ps accuracy, you need a seriously stable lab environment > or a different counter. > > Given that you plan to use the SR620 with high-end GPS gear I would > suggest you try this quick experiment for yourself to see what *your* SR620 > does, with *your* inputs, in *your* environment. Your numbers will come out > different than mine; but the methodology is the same. Your procedures can > then be based on measurement and confidence instead of guesswork and > folklore. > > Note also if your data collection is automated, there's really no reason > to wait after power-up at all. Just collect data as soon as you can and > skip the predetermined number of samples. I can send you the SR620 GPIB > scripts I used for my test. This way you have a record of the warm-up > settling time itself, which further gives you confidence in the data that > follows. > > /tvb > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- --Eric _________________________________________ Eric Garner _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
