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