The NIST-4 Watt Balance (IMAGE)

National Institute of Standards and Technology (NIST)

The NIST-4 Watt Balance

Caption

The NIST-4 watt balance has measured Planck's constant to within 34 parts per billion, demonstrating that the high-tech scale is accurate enough to assist with 2018's planned redefinition of the kilogram.

Credit

J. L. Lee/NIST

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