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-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. > _______________________________________________ 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.