World Metrology Day 2019

Posted on 20th May 2019

The theme chosen for this year is The International System of Units – Fundamentally Better. It was chosen in November last year and the effects will come into place from today.

This year, we will see one of the most significant changes applied to the SI units. The units will now be based upon a set of definitions linked to the laws of physics, while being compliant for further changes in science and technology in the future. In short, the SI units need to be able to keep up with anything future advancements may hold.

As science and technology are constantly evolving and changing around us, the need for accurate measurements is more important than ever before. The SI units will now be defined in constants of nature. For example, a constant of nature is the speed of light. By having seven constants for the seven units, the SI definitions will remain stable.

The revision will see new definitions being brought to the ampere, kilogram, kelvin (Celsius) and mole.

The Revision in Detail

Although the changes to the SI units will go largely unnoticed in day-to-day life, those who make measurements such as scientists and engineers will have to adhere to them.

  • The kilogram will be defined in terms of the Planck (h).
  • The ampere will be defined in terms of the elementary charge (e).
  • The kelvin will be defined in terms of the Boltzmann constant (k).
  • The mole will be defined in terms of the Avogadro constant (NA).

The three remaining SI units (second, metre and candela) are already defined by physical constants.

How will the Revision Affect CoMech?

From today, alongside many organisations around the world, CoMech Metrology will be using the revised and constant measurement definitions within our procedures involving calibrations, repairs, maintenance and any other process within the business.

The revision will also ensure that our measurement practices will remain accurate for the future. The Si units will remain a constant reference for all the measurements being carried out henceforth.

This is the most significant change the SI units will have seen since their implementation in 1960. This change will safeguard the rules surrounding measurements for the years to come.

Did you like this article? Share it!


  • Calibration
  • Innovation
  • Design
  • Supply Chain
  • Technology