[time-nuts] nubie querie

Bob Camp lists at rtty.us
Fri Mar 5 14:28:49 UTC 2010


Hi

Even defining when the sand timer is "done" is not a real simple thing. Waiting for that very last particle to drop may not be the best approach. 

Bob


On Mar 5, 2010, at 9:20 AM, Tom Holmes, N8ZM wrote:

> tvb...
> 
> 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!
> 
> Regards,
> 
> Tom Holmes, N8ZM
> Tipp City, OH
> EM79xx
> 
> -----Original Message-----
> 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
> 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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