[time-nuts] Re: What everyday uses are there for accurate clocks?

[Andy Talbot]

The kilogram was sorted a couple of years ago.
It is now defined in terms of teh Planc constant which has been declared as
a fixed value
All the other SI units are defined the same way now - by fixing the
physical constants  = and all referring back to the second.

https://physicsworld.com/a/new-definition-of-the-kilogram-comes-into-force/#:~:text=The%20kilogram%20is%20now%20defined,such%20as%20the%20Kibble%20balance
.

Andy
www.g4jnt.com



On Tue, 29 Nov 2022 at 19:33, Oz-in-DFW via time-nuts <
time-nuts at lists.febo.com> wrote:

> On 11/28/2022 8:45 PM, Dr. David Kirkby via time-nuts wrote:
> > I mentioned to someone the other day that I owned an HP GPS time and
> > frequency standard. He asked me a simple question, but one I didn’t know
> > the answer to.
> >
> >
> > Apart from GPS, what in the daily lives of the general public need the
> sort
> > of accuracy one can get from time-nut grade clocks? I believe some
> > financial transactions is one application, and the cellular phone system
> > another. Are there others?
> Aside from Communication and astronomy, accurate time is a fundamental
> measure used in the establishment of many other dimensions. Current and
> Length are both defined with time as component.  Improved accuracy of
> time improves the accuracy of those other measures.  I believe the only
> measure that uses a physical item as it's reference is mass in the form
> of /*the */kilogram, and there is a lot of work going into eliminating
> that need.
>
> As for things that need accurate clock, the question becomes how accurate?
>
> If we use "better than NTP" as a reference there are a host of
> industrial applications that synchronize machinery.  High speed roll
> fed multistage printing presses need to have the stages synchronized to
> prevent from piling paper up, or shredding it.  Any similar process flow
> of continuous material needs PTP level synch - so wire drawing, metal
> sheet mills, paper mills, and so on.  Older versions of these used
> timing shafts which limited ramp rates and had propagation problems
> related to shaft flexure that limited the size of systems. Application
> of mechanical buffers was used to some degree, but they have their own
> problems.
>
> Traffic flow management like trains and highways require far higher
> accuracy than I expected. It's required to maintain safety at high flow
> rates and optimize capacity. The incremental cost of rail capacity is
> not small. I expected the need to be ~10 sec accuracy and its often more
> like 10 milliseconds for high volume passenger rail and highways.
>
> --
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>
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