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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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Author Photo by Richard Steiner (The original uploader was Greg L at English Wikipedia.)
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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 NIST’s Watt balance. The vacuum chamber dome can be seen above the apparatus. Photo by Richard Steiner


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17 October 2007

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current12:54, 23 July 2008Thumbnail for version as of 12:54, 23 July 2008550 × 474 (287 KB)File Upload Bot (Magnus Manske) {{BotMoveToCommons|en.wikipedia}} {{Information |Description={{en|The NIST’s Watt balance. The vacuum chamber dome can be seen above the apparatus. Photo by Richard Steiner}} |Source=Transferred from [ en.wikipedia]; transferr
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