One Kg Quartz Resonator
Hi
Not having a bar sitting here to play with, it's hard to tell how the bar is mounted. If it's mounted by the points on the disks, then they must be non-moving nodal points. If that's what they are, I'm a bit surprised that the bar has nodes at the ends.
Bob
On Jan 23, 2013, at 6:57 PM, Fabio Eboli fabioeb@quipo.it wrote:
Il 2013-01-23 13:39 Bob Camp ha scritto:
the mode that the bar is resonating in, it's a bit hard to guess where
the nodes will be. Just looking at the bar, you wouldn't guess that
the end points would be nodes...
Bob
Sorry Bob I didnt understand last part.
You say that the end faces are nodes that move very little?
Or that it's hard to tell the way they move?
I asked that because reading the patent, I understand
that the plates are trimmed to stay near the rod and
not touching it, to give costant air reflection behaviour.
And talks about supersonic movement of the air, so I
was wondering why that was only a problem on end faces
and not on other "long" faces of the rod.
Thanks,
Fabio.
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On 1/23/2013 3:34 AM, Magnus Danielson wrote:
On 01/23/2013 02:32 AM, Mike S wrote:
Can you have a Cs under zero acceleration and at zero temperature, the
only conditions for which the second is defined? Since most metric units
are derived from the definition of the second, are any "primary
standards," in your opinion?
Isn't it defined for zero sea-level, that is standard acceleration?
"At its 1997 meeting the CIPM affirmed that:
This definition refers to a caesium atom at rest at a temperature of 0
K." - http://www.bipm.org/en/si/si_brochure/chapter2/2-1/second.html
Sea-level would be 1 g of acceleration, would it not?
On 1/24/13 7:24 AM, Mike S wrote:
On 1/23/2013 3:34 AM, Magnus Danielson wrote:
On 01/23/2013 02:32 AM, Mike S wrote:
Can you have a Cs under zero acceleration and at zero temperature, the
only conditions for which the second is defined? Since most metric units
are derived from the definition of the second, are any "primary
standards," in your opinion?
Isn't it defined for zero sea-level, that is standard acceleration?
"At its 1997 meeting the CIPM affirmed that:
This definition refers to a caesium atom at rest at a temperature of 0
K." - http://www.bipm.org/en/si/si_brochure/chapter2/2-1/second.html
Sea-level would be 1 g of acceleration, would it not?
which sea? and even if you pick a definition for sea level, g is nowhere
near constant in either magnitude or direction at that "surface".
(well, there is a "g points down normal to the surface" definition of geoid)
ANd then, there are thing like solid earth tides (so your sea level lab
is moving up and down a bit), and the local g is changing because of the
sun and moon. (moon is about 10 microg, sun half that, I think)
Such are the problems faced by people trying to get that 9+ digits of
accuracy.
Hi
Part of the process is to actually measure the local "g" and correct for it.
NIST is nowhere near the sea...
Bob
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Jim Lux
Sent: Thursday, January 24, 2013 10:38 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] One Kg Quartz Resonator
On 1/24/13 7:24 AM, Mike S wrote:
On 1/23/2013 3:34 AM, Magnus Danielson wrote:
On 01/23/2013 02:32 AM, Mike S wrote:
Can you have a Cs under zero acceleration and at zero temperature, the
only conditions for which the second is defined? Since most metric units
are derived from the definition of the second, are any "primary
standards," in your opinion?
Isn't it defined for zero sea-level, that is standard acceleration?
"At its 1997 meeting the CIPM affirmed that:
This definition refers to a caesium atom at rest at a temperature of 0
K." - http://www.bipm.org/en/si/si_brochure/chapter2/2-1/second.html
Sea-level would be 1 g of acceleration, would it not?
which sea? and even if you pick a definition for sea level, g is nowhere
near constant in either magnitude or direction at that "surface".
(well, there is a "g points down normal to the surface" definition of geoid)
ANd then, there are thing like solid earth tides (so your sea level lab
is moving up and down a bit), and the local g is changing because of the
sun and moon. (moon is about 10 microg, sun half that, I think)
Such are the problems faced by people trying to get that 9+ digits of
accuracy.
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.
On 1/24/2013 10:38 AM, Jim Lux wrote:
On 1/24/13 7:24 AM, Mike S wrote:
On 1/23/2013 3:34 AM, Magnus Danielson wrote:
On 01/23/2013 02:32 AM, Mike S wrote:
Can you have a Cs under zero acceleration and at zero temperature, the
only conditions for which the second is defined? Since most metric
units
are derived from the definition of the second, are any "primary
standards," in your opinion?
Isn't it defined for zero sea-level, that is standard acceleration?
"At its 1997 meeting the CIPM affirmed that:
This definition refers to a caesium atom at rest at a temperature of 0
K." - http://www.bipm.org/en/si/si_brochure/chapter2/2-1/second.html
Sea-level would be 1 g of acceleration, would it not?
which sea?
OK, "roughly 1 g," but that's missing the point. Which is, a real-world
device that realizes the definition of the second is (currently?)
impossible. That TAI is a weighted average of many "standards" I think
supports that - real world devices must be compensated to be close, but
still imperfect.
My question was in response to a claim that if "the number and type of
atoms in such a standard" (proposed 1 kg silicon sphere) couldn't be
counted, "its not a primary standard." The same logic could be applied
to the second, and all derived units.
Hi
I think a better analogy would be:
There don't have to be exactly X atoms in the Avogadro ball for it to be a
standard. You simply have to know how many relative to X in order to correct
for your gizmo. The gotcha obviously is you need the count of each isotope.
The same sort of issue applies to a cesium. You actually measure gravity
(and several other things) and correct for them. If there was no way to
measure your local gravity (or magnetic field), you would have a lot of
trouble using Cs as a primary standard.
That said, the currently accepted primary mass standard is simply an
arbitrary lump of metal. It does not connect to anything other than it's
self. That's not a good thing at all.
Bob
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Mike S
Sent: Thursday, January 24, 2013 11:50 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] One Kg Quartz Resonator
On 1/24/2013 10:38 AM, Jim Lux wrote:
On 1/24/13 7:24 AM, Mike S wrote:
On 1/23/2013 3:34 AM, Magnus Danielson wrote:
On 01/23/2013 02:32 AM, Mike S wrote:
Can you have a Cs under zero acceleration and at zero temperature, the
only conditions for which the second is defined? Since most metric
units
are derived from the definition of the second, are any "primary
standards," in your opinion?
Isn't it defined for zero sea-level, that is standard acceleration?
"At its 1997 meeting the CIPM affirmed that:
This definition refers to a caesium atom at rest at a temperature of 0
K." - http://www.bipm.org/en/si/si_brochure/chapter2/2-1/second.html
Sea-level would be 1 g of acceleration, would it not?
which sea?
OK, "roughly 1 g," but that's missing the point. Which is, a real-world
device that realizes the definition of the second is (currently?)
impossible. That TAI is a weighted average of many "standards" I think
supports that - real world devices must be compensated to be close, but
still imperfect.
My question was in response to a claim that if "the number and type of
atoms in such a standard" (proposed 1 kg silicon sphere) couldn't be
counted, "its not a primary standard." The same logic could be applied
to the second, and all derived units.
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.
Hi,
It would seem to me that since the second is(was) defined
relative to a specific number of resonances of a C-beam at a
specific gravity, and inertial frame of reference, that any
deviation from the defined value is an indication of not
the error in your C-beam, but rather the error due to your
location.
Perhaps the corrections are inappropriate?
-Chuck Harris
Bob Camp wrote:
Hi
I think a better analogy would be:
There don't have to be exactly X atoms in the Avogadro ball for it to be a
standard. You simply have to know how many relative to X in order to correct
for your gizmo. The gotcha obviously is you need the count of each isotope.
The same sort of issue applies to a cesium. You actually measure gravity
(and several other things) and correct for them. If there was no way to
measure your local gravity (or magnetic field), you would have a lot of
trouble using Cs as a primary standard.
That said, the currently accepted primary mass standard is simply an
arbitrary lump of metal. It does not connect to anything other than it's
self. That's not a good thing at all.
Bob
Hi
If you take the position that a primary standard is only functional if it's
under the ideal nominal conditions - you have no primary standards at all.
They all require corrections of one sort or the other. Having a system with
no standards is not a system at all...
The practical approach is to define the ideal conditions in a way that you
can indeed correct back to them. The most common way is to take the
contribution to zero. There obviously are other approaches. Regardless of
weather you take it to zero or x.xxx the net result is the same, as long as
everybody does the same thing.
Bob
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Chuck Harris
Sent: Thursday, January 24, 2013 12:56 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] One Kg Quartz Resonator
Hi,
It would seem to me that since the second is(was) defined
relative to a specific number of resonances of a C-beam at a
specific gravity, and inertial frame of reference, that any
deviation from the defined value is an indication of not
the error in your C-beam, but rather the error due to your
location.
Perhaps the corrections are inappropriate?
-Chuck Harris
Bob Camp wrote:
Hi
I think a better analogy would be:
There don't have to be exactly X atoms in the Avogadro ball for it to be a
standard. You simply have to know how many relative to X in order to
correct
for your gizmo. The gotcha obviously is you need the count of each
isotope.
The same sort of issue applies to a cesium. You actually measure gravity
(and several other things) and correct for them. If there was no way to
measure your local gravity (or magnetic field), you would have a lot of
trouble using Cs as a primary standard.
That said, the currently accepted primary mass standard is simply an
arbitrary lump of metal. It does not connect to anything other than it's
self. That's not a good thing at all.
Bob
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Hi Bob,
It seems to me that all of our current primary standards
are only functional under the ideal nominal conditions.
Which ones aren't?
-Chuck Harris
Bob Camp wrote:
Hi
If you take the position that a primary standard is only functional if it's
under the ideal nominal conditions - you have no primary standards at all.
They all require corrections of one sort or the other. Having a system with
no standards is not a system at all...
The practical approach is to define the ideal conditions in a way that you
can indeed correct back to them. The most common way is to take the
contribution to zero. There obviously are other approaches. Regardless of
weather you take it to zero or x.xxx the net result is the same, as long as
everybody does the same thing.
Bob
Hi
If the standard only functions unreachable conditions, then you have no
standard.
The point is that you do operate them under normal conditions, and then
correct the result as required. I do not know of any primary standards that
are totally un-influenced by their environment in any way. That of course
doesn't mean there are none...
Bob
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Chuck Harris
Sent: Thursday, January 24, 2013 2:40 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] One Kg Quartz Resonator
Hi Bob,
It seems to me that all of our current primary standards
are only functional under the ideal nominal conditions.
Which ones aren't?
-Chuck Harris
Bob Camp wrote:
Hi
If you take the position that a primary standard is only functional if
it's
under the ideal nominal conditions - you have no primary standards at all.
They all require corrections of one sort or the other. Having a system
with
no standards is not a system at all...
The practical approach is to define the ideal conditions in a way that you
can indeed correct back to them. The most common way is to take the
contribution to zero. There obviously are other approaches. Regardless of
weather you take it to zero or x.xxx the net result is the same, as long
as
everybody does the same thing.
Bob
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