[time-nuts] nubie querie

Tom Van Baak tvb at LeapSecond.com
Fri Mar 5 06:43:57 UTC 2010


> In the last slide you show a sand timer.  Do you have accuracy data for it?

Hi Brooke,

The past 3 hours the "one hour" timer measures 56:24,
56:19, and 56:30. That's at 67 F room temp. Somewhere
I have enough clean data to compute the ADEV; it's more
stable than accurate.

It also has a tempco (one day when my wife wasn't looking
I collected data inside the kitchen refrigerator, and oven).

I would guess it has very little dependence on barometric
pressure or humidity since all the sand is sealed inside the
blown glass bulb.

Eventually I will mechanically automate the hourly turn-over
and get 24x7 long-term data. If I also model the tempco it
may be possible to temperature compensate the rate error.

I don't know where the flicker floor will be. My prediction is
this hour-glass will gradually speed up as the glass or the
sand slowly wear over time.

/tvb






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