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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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19th Nov 2009, 10:21 pm | #1 |
Retired Dormant Member
Join Date: Sep 2008
Location: Harrogate, North Yorkshire, UK.
Posts: 352
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The Watt balance and the search for the kilogram
It is refreshing to read that one of the most advanced state of the art experimental machines for providing an accurate definition of the kilogram uses current-carrying coils and Faraday's law of induction.
Vintage electronics is alive and well. http://en.wikipedia.org/wiki/Watt_balance |
19th Nov 2009, 11:46 pm | #2 |
Rest in Peace
Join Date: Nov 2004
Location: Antwerp, Belgium
Posts: 345
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Re: The Watt balance and the search for the kilogram
There was once a lump of platinum-iridium alloy in France which we all believed in.
No problem with "progress", but don't anyone get carried away ....! |
20th Nov 2009, 11:42 am | #3 |
Dekatron
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
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Re: The Watt balance and the search for the kilogram
But surely this depends on the value of g being the same all along the balance beam? Even my school teachers couldn't agree on g ..... we would use 9.8 in maths (where we were using 22/7 for π and no calculators) or 10 in physics and CDT (where we were using calculators, and they already had a button for π. I remember my own calculator had several other fundamental constants, but g was not among them).
I always thought they were going to redefine the kilogram in terms of Avogadro's constant. I can just see some hapless lab technician having to count out 602 300 000 000 000 000 000 000 individual atoms of carbon-12 ..... and making sure there's no carbon-14 in there .....
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If I have seen further than others, it is because I was standing on a pile of failed experiments. |
20th Nov 2009, 7:11 pm | #4 |
Retired Dormant Member
Join Date: Sep 2008
Location: Harrogate, North Yorkshire, UK.
Posts: 352
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Re: The Watt balance and the search for the kilogram
The British engineering breakthrough that establishes exactly how much mass there is in a kilogram has been sold to Canada.
http://www.eurekamagazine.co.uk/arti...e-problem.aspx according to the article the uncertainty is enough to put a space probe off course (I don't think that this is going to be a problem to most of us seeing that I can't remember the last time that I plotted the flight path of a space ship). The machine was first designed to define the amp in terms of the metre, kilogram and second. I assume that the amp can now be defined in terms of Planck's constant(?), the second and metre can be defined to high degrees of accuracy which working backwards allows you to calculate the kg. It would be interesting to create some of the early vintage instruments. |