Hi Jim, If you are looking for low power (< 80 mW @ 24 degrees C), stable (better that 1ppb per day) & accurate (within 5ppb of 1Hz from factory) then have a look at these devices.
They also have an input pin that takes a GPS 1pps ref used to discipline them. (Used by the device to recalibrate itself.) www.l-3com.com/nautronix/products/hptr.html www.l-3com.com/nautronix/pdfs/HPTR_Rev_2.1.pdf Regards Luke Hoffmann -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Jim Palfreyman Sent: Thursday, 27 May 2010 12:22 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Most accurate small crystal Hi All, I have a RSA SecurID device which I use to log in to my work's VPN. For those of you not familiar with these, they show you a 6 digit number that you use (combined with a PIN) to log in. This number changes every minute. The changing of this number lines up with the servers at the other end and, as I understand it, they do take into account gradual drift. These devices have a limited programmed lifetime of three years as well. So the internal clock on one of these needs to be decent. I have timed the accuracy of this internal clock and have found it to be pretty good so far. 17 days ago it was ticking over at 21.8 sec past the minute and a quick visual inspection today and it was still *very* close to that. I will confirm it properly tonight. Now this device travels around with me, like a wristwatch, but is not on my person. It is usually in my laptop bag. So it is subject to quite varying temperatures. So it's been nearly 3 weeks and this device has barely changed 0.1 to 0.2 secs tops. Now that's not bad compared to digital watches. I presume it has a quartz crystal in it, obviously no oven, but my question is: What is the best crystal you can get on the market today that would work in a watch type device with very little power available? What's the best accuracy that can be expected? I know straight out of the factory they can be pretty spot on (as my Casio G Shock was) but it has aged markedly and now gains a couple of seconds a week. So what is the best we can expect long term too? Regards, Jim Palfreyman _______________________________________________ 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.
