massastandardit

Massastandardit, often translated as mass standards, are highly precise physical objects used to define and realize units of mass. The most fundamental mass standard is the International Prototype of the Kilogram (IPK), also known as "Le Grand K." This cylinder, made of a platinum-iridium alloy, was historically the sole definition of the kilogram. Its mass is maintained under strict conditions at the International Bureau of Weights and Measures (BIPM) in Sèvres, France.

However, the reliance on a physical artifact for the definition of a fundamental unit like the kilogram presented challenges, including the potential for its mass to change over time. Consequently, in 2019, the kilogram was redefined based on fundamental physical constants. Specifically, it is now defined by fixing the numerical value of the Planck constant, h, to 6.62607015 × 10⁻³⁴ J⋅s (joule-seconds). This redefinition means that while physical mass standards are still crucial for practical metrology and calibration, they no longer serve as the ultimate definition of the kilogram.

In practice, laboratories and industries use a hierarchy of mass standards. These range from primary standards, which are calibrated against the IPK or the new constant-based definition, down to working standards used for routine calibrations. These standards are made from stable materials and are manufactured to very tight tolerances to ensure accuracy and reproducibility. They are essential for a wide range of applications, including scientific research, industrial quality control, and trade. The accuracy of these standards underpins the reliability of measurements worldwide.