The mini Kibble balance will measure 10 grams to a few ten-thousandths of a percent accuracy
By Emily Conover | ScienceNews
A tabletop device makes the new definition of the kilogram more accessible. Previously, the kilogram had been equal to the mass of a special metal cylinder kept in a vault near Paris. But researchers did away with that standard on May 20, pegging the kilogram instead to a quantum mechanical number known as the Planck constant (SN Online: 5/20/19).
Using that new definition, scientists at the National Institute of Standards and Technology in Gaithersburg, Md., created a scaled-down version of a device called a Kibble balance to directly measure masses of several grams via the Planck constant. When the prototype’s kinks are worked out, the apparatus should be accurate to a few ten-thousandths of a percent, researchers report in the June IEEE Transactions on Instrumentation and Measurement.
A full-scale Kibble balance requires its own laboratory space, costs millions of dollars to build and demands Ph.D.s to run it. But the new, suitcase-sized Kibble balance is just over half a meter tall, with a price tag around $50,000. That puts it within reach for pharmaceutical companies, for example, which must accurately dole out small drug dosages.