[time-nuts] nubie querie

[Tom Holmes, N8ZM]

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



_______________________________________________
time-nuts mailing list -- time-nuts at febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.