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Hi Paul -

Just to be sure I understand, are the numbers you show seconds or
tenths of a minute - i.e., for July 2008, does .50 mean 50 seconds or
30 seconds?

I have a 7-year-old $20.00 Casio which I hardly ever wear. It's very
slowly gaining. Last January it was 27 seconds fast, now it's 31
seconds fast.

I'm nowhere near as disciplined as you are about recording data, so
thank you for providing a benchmark.

Hewitt

On 1/11/09, Paul Hirose  wrote:
>
>  It may be interesting to look at the seasonal variations in daily rate
>  of an ordinary battery powered wall clock. I check this clock monthly,
>  so the values are the average daily rate for the month. All values are
>  positive, i.e., the clock always runs fast.
>
>       2006  2007  2008
>  Jan   .40   .38*  .37
>  Feb   .40   .45   .39
>  Mar   .38   .46   .44
>  Apr   .43   .46   .45
>  May   .47   .50   .50
>  Jun   .48   .52   .52*
>  Jul   .40   .48   .50
>  Aug   .48   .48   .49
>  Sep   .47   .50   .52
>  Oct   .44   .47   .49
>  Nov   .41   .41   .46
>  Dec   .35   .38   .41
>
>  * new battery installed at beginning of this month
>
>
>  And here are values for a $25 Timex digital watch I bought in 2000. It
>  still has the original battery. I don't wear this watch a lot; probably
>  less than 5 hours per week.
>
>       2006  2007  2008
>  Jan   .43   .41   .42
>  Feb   .40   .42   .42
>  Mar   .41   .43   .45
>  Apr   .41   .41   .43
>  May   .39   .41   .42
>  Jun   .34   .40   .38
>  Jul   .26   .35   .34
>  Aug   .35   .34   .34
>  Sep   .40   .40   .40
>  Oct   .43   .45   .43
>  Nov   .43   .44   .46
>  Dec   .41   .43   .44
>
>
>  The time checks are by eye and ear using WWV on a cell phone. By
>  comparing the phone audio to the audio from a shortwave receiver I've
>  found that the phone is consistently 1/4 second late, as well as I can
>  estimate, so this constant is disregarded.
>
>  My monthly error checks are accurate to perhaps 1/4 second, so the
>  corresponding daily rate is probably accurate to plus or minus .01 second.
>
>
>  --
>  I block messages that contain attachments or HTML.
>
>
>
>  >
>

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