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| Electronic Kilogram |
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NIST physicist Richard Steiner positions a mass standard at a special NIST facility designed to help redefine the kilogram in terms of current and voltage. Mass is the only one of the seven basic measurement standards that is still defined in term of a physical artifact, a century-old platinum-iridium cylinder weighing one kilogram that is housed in a special vault in France. NIST's electronic kilogram project aims to stabilize mass-related measurements over the next several decades by defining mass through electrical and other electronic standards (such as lasers). The two story high apparatus works on the same magnetic principles as electric motors and generators. It measures, with great precision, how much current passes through a wire coil in a strong magnetic field to balance the pull of gravity on a one-kilogram mass standard, and how much voltage is generated by moving the coil. Separate systems in the laboratory determine reference levels for voltage and gravity.
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Copyright is owned by the photographer. This photo is available without charge for use in materials that describe NIST programs directly. All other uses require permission from the photographer. For further information or to receive a high resolution version of this image contact: inquiries@nist.gov, (301) 975-6478 |
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Electronics and Electrical and Engineering Laboratory
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