Watt_balance,_large_view.jpg
Summary
Description Watt balance, large view.jpg |
English:
The
Watt balance
at the US
National Institute of Standards and Technology
(NIST). This is an experimental, extremely accurate mass measuring instrument. The vacuum chamber dome, above the apparatus, descends during use so it operates in vacuum. The Watt balance measures mass by comparing it to atomic units,
Planck's constant
and the speed of light. It is being developed to provide a more accurate standard of mass than the current one. Currently the primary standard defining all the world's mass and weight units is the
International Prototype Kilogram
(IPK), a cylinder of platinum-iridium alloy kept in a vault at Sevres, France. It is the only unit defined by a physical artifact, so it is vulnerable to damage and deterioration over the years, and in fact has been found to vary in mass. When it is perfected, the Watt balance will be used to "weigh" the IPK, defining the kilogram by atomic units so a physical prototype will not be needed, creating an "electronically" defined kilogram.
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Date | 17 October 2007 (original upload date) | ||
Source | Transferred from en.wikipedia to Commons by Mormegil using CommonsHelper . | ||
Author | Photo by Richard Steiner (The original uploader was Greg L at English Wikipedia .) | ||
Permission
( Reusing this file ) |
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Licensing
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License , Version 1.2 or any later version published by the Free Software Foundation ; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License . http://www.gnu.org/copyleft/fdl.html GFDL GNU Free Documentation License true true |
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This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license. | |
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This licensing tag was added to this file as part of the GFDL licensing update . http://creativecommons.org/licenses/by-sa/3.0/ CC BY-SA 3.0 Creative Commons Attribution-Share Alike 3.0 true true |
Original upload log
The original description page was
here
. All following user names refer to en.wikipedia.
- 2007-10-18 00:38 Greg L 550×474×8 (293997 bytes)
- 2007-10-17 23:51 Greg L 550×484×8 (236377 bytes)
- 2007-10-17 23:35 Greg L 500×412×8 (199416 bytes) The NISTâs Watt balance. The vacuum chamber dome can be seen above the apparatus. Photo by Richard Steiner