A clock using the 60 hz frequency of the mains in the US is accurate. This
is because each day the power grid is adjusted to insure the proper average
frequency is 60 hz. at any time the frequency may not be exact but it is
compensated so that long term it is correct.



At 11:34 AM 3/10/97 +0500, Vishram sarurkar wrote:
>On Mon, 10 Mar 1997, TONY NIXON 54964 wrote:
>
>> I need to make a clock that is accurate. It will be powered by the
>> mains, and I thought of using this as a time base as it is a fairly
>> stable waveform.
>>
>> Does anyone else know of a way which will be more accurate?
>>
>> Regards
>>
>> Tony.
>>
>hello,
>        i don't think using the mains for refrence frequency will give
>you a stable clock. if you are using PIC for the clock the best idea is
>to put it in some delay loop and keep on counting the number of passes.
>PIC being driven by a crystal oscillator will give much more stable clock.
>
>vishram.
>
>----------------------------------------------------------------------
>Life is like an onion: you peel off layer after layer, then you find
>there is nothing in it.
>----------------------------------------------------------------------
>
>                +------------------------------------------+
>                |            Vishram A. Sarurkar           |
>                |           ^^^^^^^^^^^^^^^^^^^^^          |
>                |     another hobbyist turned researcher   |
>                |   slogging @ Indian Institute of Science |
>                |               -----------                |
>                |    e-mail:vish@isu.iisc.ernet.in.        |
>                |    Phone:+91 (080) 3092487.              |
>                +------------------------------------------+
>
>
Larry G. Nelson Sr.
L.Nelson@ieee.org
http://www.ultranet.com/~nr