At 03:04 PM 2/14/00 +1300, Russell wrote: >The post below gives me an originalish idea. >What you are really trying to achieve is a completely accurate timebase / >clock over along period. > >I understand that power companies measure total cycles sent in a day and >make up the time so that long term there are on average 50 (r 60) cycles per >second. I imagine that any making up of time is achieved gradually but >chances are any change in the rate of change occurs after the ?daily >measurement. IF this is still how they do it (rather than just locking the >system to a high accuracy standard) and IF the time at which changes are >made is constant or nearly so, you may be able to use this to confirm the >absolute tome of day. Probably too many IFs but ... > >Obviously, once you are attached to a powered on mains circuit, your time >keeping problems are over. You may be able to calibrate your local >oscillator long term against the mains so that you can allow for errors >during periods of mains outage. This is the standard method used in AC-powered electric clocks. The power companies will regulate the oscillator to make up time for short outages, so AC-powered clocks (synchronous motors) are always reasonably accurate. This method (catch up on cycles) is not used once a significant (> 5 min?) outage occurs, so the clocks would need to be reset after that occurred. So your idea would suffer from the same defect: your clock will have to be eventually reset after a significant outage. As long as you would need a reset function, you might as well just stick with a crystal oscillator. Alternatively, you could use RF or internet access to get to the Ft. Collins broadcast or the Naval Observatory website or proxies. ================================================================ Robert A. LaBudde, PhD, PAS, Dpl. ACAFS e-mail: ral@lcfltd.com Least Cost Formulations, Ltd. URL: http://lcfltd.com/ 824 Timberlake Drive Tel: 757-467-0954 Virginia Beach, VA 23464-3239 Fax: 757-467-2947 "Vere scire est per causae scire" ================================================================