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
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
Don Collie jnr wrote:
I`m not sure that questions like these is welcome on this list, but here goes anyway :
1/ What are the the 10 sources of the most constant [invariant] frequencies
known to man, in order of decreacing constancy? Four immediately come to mind.
I vaguely remember reading
Hi
Then there's the phase noise of the pulsar oscillator
-
For a simple crystal oscillator the two word answer might be Leeson's model.
That of course is a cop out since it clearly defines multiple things that
contribute to phase noise.
Bob
On
If the time duration of the sand timer is defined as when the first
grain of sand lands
on the bottom, until the last grain of sand lands on the pile of sand on
the bottom,
maybe an optical circuit may sense the passing and interruption with a
light beam.
Possibly the optical sensor mounted
The variability will depend on friction between particles and the last
particle's physical slide down the glass!
At 05-03-10, you wrote:
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
Hi
So can you / do you actually *see* the last grain in the hourglass in question?
If we are looking at something that is not observed in normal operation we
have re-defined the function of the device.
Bob
On Mar 5, 2010, at 10:50 AM, Raj wrote:
The variability will depend on friction
Google USB Hourglass or visit http://home.comcast.net/~hourglass/ and you
will see that it has already been done. His application was as a random
number generator. Should be available as a kit soon...
All of this reminds me of a cartoon I saw ages ago, I think was called BC.
Characters were from the cave-man era. Regardless, in one cartoon there is a
guy sitting in the middle of a desert. His friend comes up and asks him what
he is doing. The guy replies that he is going to count all of the
At 10:25 AM -0800 3/4/10, Brooke Clarke wrote:
Hi Tom:
In the last slide you show a sand timer. Do you have accuracy data for it?
Wouldn't that depend on the consistency with which the human flips
the hour glass? They don't flip themselves, you know.
--
--David Forbes, Tucson, AZ
You've not seen me on a bad day - I've been known to flip quite often!
:-)
Dave
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of David Forbes
Sent: 05 March 2010 16:20
To: Discussion of precise time and frequency measurement; Tom Van
Like it very well
On Fri, Mar 5, 2010 at 11:12 AM, Mark Sims hol...@hotmail.com wrote:
Google USB Hourglass or visit http://home.comcast.net/~hourglass/ and
you will see that it has already been done. His application was as a
random number generator. Should be available as a kit soon...
Thought from an interloper:
It would seem to me that the best reference point would be the
instant a piece of sand leaves a specific point from the restricted
center, the spout. In pondering over the methodology it would
appear that the first piece of sand would hit the bottom of the
vessel
FWIW I have seen a lot of failures of these units in both Trak and Odetics
units.
Item is being sold as is. Not sure how much I'd want to offer.
Rob K
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Mark Sims
Sent: 05 March 2010 1:37
rich...@karlquist.com said:
I vaguely remember reading that pulsars have some fantastic stability
like 1E-20. I don't remember how they established this.
Do you remember how long ago you read that? It might have been some
handwaving back before they had good data.
For a while, the
I vaguely remember reading that pulsars have some fantastic
stability like 1E-20. I don't remember how they established
this.
Rick,
See: http://www.leapsecond.com/museum/pulsar for some
pulsar ADEV stability plots and links to many research papers
with all the details.
/tvb
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
Correct. Marking time with an hour glass is not that different
from marking time with a 1PPS. Each signal has a rise time;
one picks the
OK then if you ground up cesium azide and put it in the hour glass wouldn't
you have a cesium clock at much lower cost (And accuracy) then an HP??
Might last quite a while also.
On Fri, Mar 5, 2010 at 1:53 PM, Tom Van Baak t...@leapsecond.com wrote:
Even defining when the sand timer is done is
Hi
A clock and a hazmat site all rolled into one.
Bob
On Mar 5, 2010, at 2:41 PM, paul swed wrote:
OK then if you ground up cesium azide and put it in the hour glass wouldn't
you have a cesium clock at much lower cost (And accuracy) then an HP??
Might last quite a while also.
On Fri,
Plus the effect of a star quake when the crystalline crust rearranges
itself.
Somewhat analogous to a crystal jump.
Bruce
Bob Camp wrote:
Hi
Then there's the phase noise of the pulsar oscillator
-
For a simple crystal oscillator the two word answer
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
You could measure of the weight of the hourglass.
Phil
___
time-nuts mailing list --
Eh, does the weight change if the sand runs from top to bottom? Some
quantum mechanic effect I am missing? Or maybe a change in gravity as
the sand drops from high to low?
phil wrote:
Even defining when the sand timer is done is not a real
simple thing. Waiting for that very last particle to
Yes it does due to the variation of gravitational attraction between the
object and the Earth with height above the ground.
However this classical effect is very small and probably virtually
impossible to measure.
Bruce
Gerard PG5G wrote:
Eh, does the weight change if the sand runs from top
Quoth Bruce Griffiths at 2010-03-06 07:58...
Yes it does due to the variation of gravitational attraction between the
object and the Earth with height above the ground.
However this classical effect is very small and probably virtually
impossible to measure.
So, if the mass is closer to the
Matthew Smith wrote:
Quoth Bruce Griffiths at 2010-03-06 07:58...
Yes it does due to the variation of gravitational attraction between the
object and the Earth with height above the ground.
However this classical effect is very small and probably virtually
impossible to measure.
So,
As one who has measured vague things like hourglass time to great
accuracy,
I would suggest finding a robust definition of end of flow.
This would inevitably involve watching the flow past the end of
flow to determine retrospectively
when the flow had effectively ceased.
To be fair to the
On Sat, 06 Mar 2010 08:03:01 +1030, Matthew Smith wrote:
So, if the mass is closer to the centre of the planet, it weighs more?
Never really considered this before, but fascinating nonetheless.
No!
The gravitational attraction will decrease once penetrating the surface.
At the center of gravity
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.
Correct. It's not unlike a zero crossing detector. The period
of the sand
It's all very well to talk about zero-crossing detection in an hour glass,
but you haven't got an oscillator until you have some uniform means to
flip it. Then you can talk about measuring the period (two flips) over
some useful interval.
Seems like the flip should take a second or so. Too fast
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