METTLER TOLEDO’s Redesigned M_one Supports Kilogram Redefinition Research, Becomes Comparator of Choice for World-Renowned Metrology Institute

METTLER TOLEDO’s Redesigned M_one Supports Kilogram Redefinition Research, Becomes Comparator of Choice for World-Renowned Metrology Institute

The M_one is providing high-accuracy mass determination of silicon spheres and mass standards, lending much-needed precision to the study of the redefined kilogram.

In December 2017, the new METTLER TOLEDO M_one was installed at a world-renowned National Metrology Institute in Europe. Experts at this preeminent institute expect the highly precise vacuum mass comparator to be instrumental in further research into the establishment of a redefined kilogram. They also expect the comparator to be useful in mass calibration as standards are disseminated.

The institute has been highly involved in research surrounding the potential of establishing a new mass standard, as well as the effort to secure accuracy and traceability of studied artifacts as part of the Avogadro Project. This effort to determine a constant as represented by the number of atoms in a nearly pure silicon (28Si) sphere has so far provided one of the most consistent mass measurements. Another method being researched involves use of a Watt or Kibble balance. Both methods require that artifacts be weighed and disseminated in a constant vacuum to ensure the most accurate comparisons as researchers attempt to secure the widely used SI unit to a natural constant.

The redefinition itself will occur at a very high level of accuracy. Part of the process involves creating an exacting sphere from a nearly isotope-pure 28Si crystal. Each sphere is first measured using dimensional and x-ray apparatuses. Then, the sphere is transferred under vacuum to the M_one for mass measurement. The stakes are high, as the value of a crafted and measured silicon sphere can be as high as 1,000,000 EUR.

The M_one with its newly designed Artifact Storage and Transfer Vessel (ASTV) has proved critical to the effort, making the M_one a natural choice for metrologists in this particular research/application field. The comparator itself offers a 0.1 microgram resolution and 0.3 microgram typical repeatability, while providing a constant 10-6 millibar vacuum environment for measuring the spheres. This excellent repeatability along with a flexible, six-position automatic weight-handling device enables the accurate mass determination of artefacts in a variety of shapes, including large cylinders and spheres.

The M_one determines masses from 100 to 1,000 grams without the need for disc weights, while a built-in, exchangeable adjustment/sensitivity weight adds the possibility of sensitivity checks during measurements. Additionally, the M_one’s user-friendly, Windows®-based software enables intuitive system control and secure data processing. These features, as well as the performance of existing METTLER TOLEDO comparators at the institute, have enhanced researchers’ confidence that the M_one will be able to perform with required accuracy.

The M_one offers metrology institutes modular ergonomic design and flexibility.

Image 1 Caption:

METTLER TOLEDO’s M_one is the mass comparator of choice for metrology institutes around the world.

Image 2 Caption:

A newly-designed Artifact Storage and Transfer Vessel (ASTV) allows comparisons to be made under vacuum or at constant ambient pressure. This protects highly valuable artifacts such as the isotopical-enriched silicon spheres being studied as part of the effort to redefine the international prototype kilogram (IPK).

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