Hi The only thing I'd add to that is to be very careful of where the return on the EFC voltage goes.
A "ground drop" in common between the EFC and heater current can really mess things up. A milivolt is pretty easy to come up with as the oven compensates for significant temperature change. That same milivolt getting into the EFC can also give you a very measurable frequency change. Bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Poul-Henning Kamp Sent: Monday, October 05, 2009 4:20 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] LT1763 In message <[email protected]>, John Green writes: >Thanks Poul,I had not considered that one probably because of the package. >It does look like a contender. I am considering the LT3080 because of the >tight regulation and it is available in not one, but 2 power packages. The >tab is tied to the output though. The max current is around 300 mA cold and >less than 100 mA warm. The oscillator seems to have a regulator inside >already but does move around with voltage changes You should pick your poison carefully here: Low noise regulators are usually not very stable, typically they are quite sensitive to temperature. Precision regulators are stable, but tend to be noisy. If your OCXO is voltage sensitive, make sure to connect the sense resistor to the terminal, right at the OCXO VCC terminal. If the heater has a separate VCC terminal on the OCXO, give it its own supply. Another trick: if you don't plan to run your OCXO in high temperatures is to insulate it thermally. That will reduce the current draw from the heaters, making regulation easier, and if done right, will also low-pass-filter the temperature excursions. But don't overdo it, it has to be able to get rid of excess heat and you may shorten the electronics life if it gets too hot. Poul-Henning -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [email protected] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ 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. _______________________________________________ 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.
