[time-nuts] 60hz disciplined watch (really?)

Bill Hawkins bill at iaxs.net
Wed Apr 20 18:33:48 UTC 2011


Group,

Google can't find anything for "citizen ecodrive watch time sync 60 hz"
except a few where the "k" was left out of "60 khz". All of the watches
that synched received WWVB at 60 KHz.

The claim of 13 millisecond accuracy from line frequency is suspect. There
is no control of the power grid to that accuracy. It is not possible.
The weekly accuracy is measured in cycles. Variation during the day
can be seconds, losing during the day and gaining at night.

It seems to me that the filtering algorithm for 60 Hz would have severe
underflow problems with floating point math in a low power processor.

Bill Hawkins




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