[time-nuts] nubie querie
Tom Holmes, N8ZM
tholmes at woh.rr.com
Fri Mar 5 14:20:13 UTC 2010
Not to kick sand in your face, but it seems that in order for your automated
turn-over device to work, as well as to accurately measure the time
intervals, you would need a means to determine when the sand quits flowing.
Possibly an accelerometer or microphone, with the added benefit of being
able to hear the close-in phase noise.
I admire your dedication to monitoring the hour long periods of the sand
timer so diligently. Truly a time-nut!
Tom Holmes, N8ZM
Tipp City, OH
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Tom Van Baak
Sent: Friday, March 05, 2010 1:44 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] nubie querie
> In the last slide you show a sand timer. Do you have accuracy data for
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.
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