Yes you are correct...for long term accuracy you need to calibrate it to a reliable frequency standard. If all you want is to generate 60 Hz the a good reference is Fairchild's Application Note 42025. There is some good info there. I use the Maxim DS32kHz oscillator on many of my projects and it is quite accurate for a clock time base.
Perhaps our wonderful government will keep the utilities doing what they are doing today....If I received anything other than an accurate 60 Hz supply from them then I will insist on some form of rebate. Time to break out my strip chart recorder and monitor my supply...regards... On 28 June, 13:25, David Forbes <[email protected]> wrote: > On 6/28/11 10:03 AM, neutron spin wrote: > > > 32.768KHz has a nice property that it oscillates 2^15 times per second > > which makes the timer math easy...I made a calc using the average > > tolerance of these crystals and came out to an accuracy of around > > 0.002 % accuracy or better - about 2 seconds a day. This of course > > does not account for temperature drift....wow...are we splitting hairs > > or seconds?...lol...regards... > > The standard 32768 Hz watch crystal has a parabolic > frequency/temperature curve, which tops out in frequency at 25C (77F) > and gets slower in either hotter or colder weather. > > Once adjusted, it's good to a couple PPM at ~20C to 30C (68F to 86F). > One PPM is 30 seconds a year, half a second per week. > > I highly recommend adjusting a crystal if you're going to use it for > timekeeping. The hairs you can split with it are much finer. > > -- > David Forbes, Tucson AZ -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
