New Delhi, May 21 (IANS): The new System of Units (SI) to measure weight, temperature, amount of substance, and current came into operation in India from Monday on the occasion of the World Metrology Day, an official release said.

The resolution to redefine four of the seven base units - the kilogram (SI unit of weight), Kelvin (SI unit of temperature), mole (SI unit of amount of substance), and ampere (SI unit of current) - was adopted at the 26th General Conference on Weights & Measures (GCWM), which is comprised of 60 member countries, in November 2018.

"This decision has now enabled scientists and researchers to base the SI units entirely on fundamental properties of nature, which will ensure their ongoing refinement and improvement for years to come," the Science and Technology Ministry Ministry said in a release.

"The fundamental constants are invariants of time and space and successfully replaced the artifact-based units, and aptly opened up the new era for quantum world by linking all seven base units to fundamental constants/quantum standards."

The existing definition of the kg is over 130 years old. The new SI system, which is defined in terms of Planck's constant, would be stable in the long term and practically realisable.

The new SI System will be helpful in bringing in accuracy while dealing with international trade, biotechnology, high-tech manufacturing and human health and safety.

The new definition of kg involves accurate weighing machines called 'Kibble balance', which uses Planck's Constant to measure the mass of an object using a precisely measured electromagnetic force.