New M_one Vacuum Mass Comparator to Support the Redefined Kilogram

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As the benchmark in mass comparison, the M_one from METTLER TOLEDO delivers results accurate to 0.1 µg with typical repeatability of 0.3 µg. The newest M_one succeeds by minimizing all sources of uncertainty from the environment, the process, and even itself during both measurement and transport, making it vital in the race to define the new kilogram.

M_one, displayed with Artefact Transfer Device and included Artefact Storage & Transporation Vessel

The M_one is famous for its reproducibility; in fact, 28 NMIs have staked their reputation on the modular METTLER TOLEDO system.

The METTLER TOLEDO M_one has long established itself as the reference instrument of choice for mass comparison under a controlled
environment. Today, improved artefact storage and transfer capabilities are helping to minimize uncertainty even better than past models, putting the newly-designed M_one at the center of the race to define a new kilogram based on physical constants.

The race to redefine the kilogram involves two experiments: one using a Watt balance and the other using the Avogadro principle. To share and disseminate the investigated artefacts, each artefact must be transferred in a contamination-free atmosphere. Eliminating human error through automation, the M_one vacuum pumping system enables the necessary controlled environment starting at ambient pressure and going down to a vacuum level of 10-6 mbar.

Ergonomic design allows users to place weights directly onto the M_one turntable through a large, quick-loading door. The system is sealed and allowed to reach desired atmospheric conditions. Once this pressurized environment is reached, the artefact is never exposed to air again. A newly designed Artefact Storage and Transport Vessel (ASTV), Artefact Transfer Device (ATD), and automatic Load Lock arm facilitate easy transfer of the artefact and preserve the pressure required to deliver necessary stability.

Once the artefact reaches the measurement chamber during comparisons, it is placed on a star-shaped weighing pan designed to accept various artefact shapes, such as cylindrical weights and silicon spheres from 100 g – 1 kg without adapter plates. Automated Gravimetric Centering (AGC) ensures correct positioning, minimizing eccentricity and ensuring the highest possible repeatability.

The M_one is famous for its reproducibility; in fact, 28 NMIs have staked their reputation on the modular METTLER TOLEDO system. Extensive M_one adoption is further enhancing redefinition efforts by allowing artefact intercomparisons at minimized uncertainty.

METTLER TOLEDO is proud that M_one technology is leading the way to a higher level of weighing accuracy in current efforts to redefine the kilogram. To learn more about the M_one’s role in the effort, or to discover how an NMI, governmental, or research organization can obtain this specialized technology, click here.

METTLER TOLEDO is a leading global manufacturer of precision instruments. The Company is the world’s largest manufacturer and marketer of weighing instruments for use in laboratory, industrial and food retailing applications. The Company also holds top-three market positions for several related analytical instruments and is a leading provider of automated chemistry systems used in drug and chemical compound discovery and development. In addition, the Company is the world’s largest manufacturer and marketer of metal detection systems used in production and packaging. Additional information about METTLER TOLEDO can be found at

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Branko Radovinovic
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