Redefinition of four basic measurements in force

Redefinition of four basic units for weight, electrical current, temperature and quantity — the kilogram, ampere, kelvin and mole — came into force in China on Monday, the top market regulator announced on the same day.

Adopting the new definitions, which are based on constants rather than physical objects to assure the stability of the units, will produce significant impact on scientific and technological progress, industrial development, economy and trade, environmental protection, health improvement and social governance, Qin Zhiyong, deputy minister in charge of the State Administration for Market Regulation, said at a ceremony in Beijing.

"The reform makes possible precise and infinite measurement, and will promote human beings' efforts in the exploration of the micro world and getting knowledge of the universe," he said. "More precise measurements will also contribute to a more fair market and trade, environmental protection, healthcare and protection of consumers' rights."

As a member state of the Meter Convention, China will continue to promote the use of the International System of Units (SI), and intensify international cooperation in metrology, he said.

The four units were redefined after a vote by member states of the International Bureau of Weights and Measures (BIPM) in November during a conference in Paris. Member states agreed to carry out the redefinition on May 20, 2019 — World Metrology Day.

The decision means all seven SI units have been defined in terms of constants that describe the natural world. The other three units — the second, meter and candela — were redefined previously.